Pertussis and Transmission

Pertussis and Transmission

 I’m sure we’ve all seen the campaign ads called “Do it for your baby”. If not, here is an example. There is also a website.

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More recently, J. Lo was recruited by Sanofi Pasteur and the March of Dimes to jump on the bandwagon and promote Pertussis vaccines for adolescents and adults.

 Let’s take a look at the issue of Pertussis transmission and what the vaccine really does or doesn’t do.

Pertussis Infection in Fully Vaccinated Children in Day-Care Centers, Israel (Emerging Infectious Diseases (Vol. 6, No. 5, September–October 2000)

 Conclusions

 The effects of whole-cell pertussis vaccine wane after 5 to 10 years, and infection in a vaccinated person causes nonspecific symptoms (3-7). Vaccinated adolescents and adults may serve as reservoirs for silent infection and become potential transmitters to unprotected infants (3-11). The whole-cell vaccine for pertussis is protective only against clinical disease, not against infection (15-17). Therefore, even young, recently vaccinated children may serve as reservoirs and potential transmitters of infection.

 

…We found that immunity does not even persist into early childhood in some cases. We also observed that DPT vaccine does not fully protect children against the level of clinical disease defined by WHO. Our  results indicate that children ages 5-6 years and possibly younger, ages 2-3 years, play a role as silent reservoirs in the transmission of pertussis in the community. More studies are needed to find the immunologic basis of protection against infection and colonization and thus an effective way to eradicate pertussis.

 Also See:

Characterization of Bactericidal Immune Responses following Vaccination with Acellular Pertussis Vaccines in Adults

booster immunization of adults with acellular pertussis vaccines was not found to increase bactericidal activity over preimmunization levels. Identifying ways to promote bactericidal immune responses might improve the efficacy of acellular pertussis vaccines.

Informal consultation on the control of pertussis with whole cell and acellular vaccines

Dr Cherry pointed out in the 1999 WHO meeting, that even with a return to high vaccination coverage in Japan, pertussis incidence in children less than three months of age, had not declined substantially.

 

Pertussis toxin inhibits neutrophil recruitment to delay antibody-mediated clearance of Bordetella pertussis 

…However, their efficacy against subclinical infection is doubtful, as the majority of vaccinated populations test positive for subsequent infection (10, 17), suggesting that the bacterium successfully infects immune and/or vaccinated individuals.

  

The Pertussis vaccines do not prevent transmission or infection. It simply prevents or suppresses the symptoms, or causes subclinical infection. The reason the vaccines do not prevent transmission is because they do not kill the bacteria that cause the disease. The vaccines only make the body able to resist the toxin that the bacteria release. The toxin is what makes a person sick and causes clinical disease. That is the reason behind the claim that being vaccinated will make a clinical case of Pertussis ‘milder’. Even if you don’t get the full effect of the vaccine, you might get partial blockage of the toxin which might cause you to cough less, etc.

What is also worth noting is the small print of an advertisement for Adacel, a DTaP booster:

“It is unknown whether immunizing adolescents and adults against pertussis will reduce the risk of transmission to infants.”

At least there was some honesty there. The adolescent or adult booster helps one person, the person who receives it! Why doesn’t the campaign advertisement just say “Do it for you!” They don’t because time as shown repeatedly that the majority of adults will not do booster vaccines. But, if they use infants or children as a reason, it works.

 Read on…

 Acellular Pertussis Vaccines and Complement Killing of Bordetella pertussis

At least one of the antigens in the acellular pertussis vaccine appears to be able to serve as a target for complement-mediated bactericidal activity. However, in this study and other studies (19, 21), improved bactericidal responses after immunization were rarely observed, possibly due to induction of antibodies that fail to fix complement. The absence of vaccine-induced bactericidal activity in vitro is consistent with the observation that the pertussis vaccine is effective at preventing severe disease, likely due to pertussis toxin neutralization and blocking attachment to reduce bacterial colonization, but it is less effective at producing a sterilizing immune response (5, 18). Despite high vaccination rates, the number of reported cases of pertussis in the United States has increased steadily since the 1980s (22). Developing a pertussis vaccine with a greater potential to elicit bactericidal activity could reduce bacterial carriage and reduce the incidence of disease.

 

 According to this study, some were less likely to be protected, and the majorities were no more likely to be protected from infection than they were before the vaccine. To boot, the vaccine made them more susceptible to infection. There was a level of protection from severe disease due to the toxoid in the vaccine. This study alone shows that the vaccine doesn’t reduce carriage of the bacteria.  Therefore, marketing the vaccines solely to protect infants isn’t being entirely truthful. It simply does not work that way. The vaccine can’t stop you from being infected, nor stop you from spreading the bacteria to infants, the immuno-compromised, the unvaccinated or vaccinated.  

 

 It is also acknowledged that the whole-cell pertussis vaccine was more efficacious, but also more reactive, hence why we now use the DTaP.

Use of Pertussis Vaccines in Outbreaks

Estimates of the efficacy of immunization with pertussis vaccines are subject to wide variation due to variation in study design, including factors such as case definition, case ascertainment, and duration of follow up. A recent study of reported cases in the United States in 1992 – 1994 estimated the effectiveness of whole-cell vaccine against culture proven pertussis; the effectiveness of three doses among children aged 7-18 months was 79% and the effectiveness of 4 doses among children aged 19-47 months was 90%.2

Estimates are also available from recent field trials that compared the efficacy of acellular and whole-cell pertussis vaccines. In these trials, the efficacy of three doses of whole cell pertussis vaccines from different manufacturers ranged from 83% to 98%, although the DTP vaccine from one manufacturer had a low efficacy in two trials (35% to 48%). In the field trials, the efficacy of the four licensed acellular vaccines ranged from 71% to 89%.

 

 

When is a true case a case… or not? How does case definition come into play?

The Science and Fiction of Pertussis Vaccines  (PEDIATRICS Vol. 104 No. 6 December 1999, pp. 1381-1383)

Case definition has been particularly problematic in all of the recent DTaP vaccine efficacy trials. For uniform comparative purposes a case definition was suggested by a WHO expert committee. This definition required 21 days of paroxysmal cough plus laboratory confirmation of pertussis in the subject or household contact. There are 2 problems with this definition. The first is that a substantial number of B pertussis infections in unvaccinated children are mild and would not meet the case definition. The second is that all pertussis vaccines tend to modify duration and severity of disease rather than completely preventing illness. Therefore, the WHO definition has made all vaccines look better than they are and it has tended to obscure differences between vaccines.

 

Easily Missed?

Whooping cough is a common respiratory infection caused by the bacterium Bordetella pertussis. It should be considered as a possible diagnosis in any adolescent or adult with an acute cough of more than two weeks’ duration, even if they have been fully immunised.

 

Whooping cough in school age children with persistent cough: prospective cohort study in primary care

 

…Studies in the United States report a 20% incidence of Bordetella pertussis infection among adults with a persistent cough.2 Despite data showing that neither infection nor immunisation results in lifelong immunity, whooping cough is seldom diagnosed in primary care because of the lack of specificity of clinical symptoms and signs. Whooping cough is perceived as a disease of very young children who have not been immunised and who have classic features such as whoop…

…General practitioners should be alert to a potential diagnosis of whooping cough in any child who presents with a persistent cough. We found that children with pertussis cough for a median of 16 weeks. Little evidence indicates that administering erythromycin to children with pertussis two weeks after they have contracted the infection either reduces symptoms or prevents transmission.10

 

Acellular Pertussis Vaccines and Complement Killing of Bordetella pertussis 

 

When examined individually, the pre- versus postimmunization bactericidal activity was not significantly different at any dilution tested for 8 of the 15 acellular vaccine recipients. The individuals in the group with unchanged activity after immunization included an individual with undetectable preimmunization activity against the wild-type strain (individual 32-60), and the individual with the highest preimmunization activity (individual 26-47) (Fig. 2). These results suggest that the level of preimmunization bactericidal activity does not necessarily influence the ability to generate a postimmunization response.

 

However, statistically significant differences between pre- and post immunization bactericidal activity were observed (P < 0.05) using the paired t test for at least one serum dilution for 7 of the 15 acellular vaccine recipients. Furthermore, evidence of both improved bactericidal activity and reduced bactericidal activity after immunization was found in these seven serum samples. Four individuals displayed improved bactericidal activity after immunization when serum was added at lower concentrations (1.0 or 0.10%) but not at 10% (Fig. 3). However, in addition to enhanced bactericidal activity, individuals 4-43 and 20-55 displayed evidence of blocking activity, since fewer bacteria were killed when serum was added at 10% than when serum was added at 1%. Blocking activity could occur when antibodies that do not fix complement compete with complement-fixing antibodies for access to antigen. More definitive evidence of blocking was demonstrated in three other individuals (Fig. 4). For these individuals, the post immunization serum samples had significantly less bactericidal activity than the pre immunization serum samples at a serum concentration of 10%.

However, in this study and other studies (19, 21), improved bactericidal responses after immunization were rarely observed, possibly due to induction of antibodies that fail to fix complement. The absence of vaccine-induced bactericidal activity in vitro is consistent with the observation that the pertussis vaccine is effective at preventing severe disease, likely due to pertussis toxin neutralization and blocking attachment to reduce bacterial colonization, but it is less effective at producing a sterilizing immune response (5, 18).

 In various studies, vaccinated children do not fit the case definition of pertussis, yet they test positive. They exhibit atypical or mild symptoms. This shows the vaccine may protect against clinical disease, but not against infection.  Vaccinated children and adults are still serving as asymptomatic reservoirs and transmit infection.  A reduction in colonization, without any kind of sterilizing immune response, is the most you will get. There should be an enhanced bacterial clearance in the vaccinated, but studies have proved there isn’t. What is even worse is, serology states that more than half of are catching pertussis every 2 1/2 years. If humans did not transmit pertussis easily, or could clear it easier, we wouldn’t have it so much. The vaccine has not changed that. Vaccinated or not, you can and do, carry and transmit the disease.

 

 Other Studies:

 

Cell-mediated immune responses to antigens of Bordetella pertussis and protection against pertussis in school children  (Pediatric Infection Disease Journal 1999; 18: 366-370)

 Abstract

Background. Increasing evidence suggests that cell-mediated immunity (CMI) is involved in immune response against Bordetella pertussis. However, there are practically no studies evaluating the significance of pertussis-specific CMI in relation to protection against clinical pertussis.

 

On pg. 366: “The immunologic mechanisms of protection against clinical pertussis are poorly understood. Although several studies have suggested that antibodies to some pertussis antigens may be predictive of protection against pertussis, there is no generally accepted laboratory measure of immunity. Further in clinical efficacy trials of acellular vaccines, no clear correlation has been found between serum antibody values and protection. 

…”In the present study, no clear association was found between serum antibody values and clinical outcome.”

 

Pertussis toxin: the cause of the harmful effects and prolonged immunity of whooping cough. A hypothesis. (Rev Infect Dis. ;1 (3):401-12 233166)

The nature of the pathogenesis and of the prolonged immunity of whooping cough has not been clearly defined. The literature of Bordetella pertussis indicated that only the antigen that induces histamine sensitization, lymphocytosis, and other biological reactions in mice is the cause of the harmful effects and prolonged immunity of whooping cough. This antigen has the general characteristics of bacterial protein exotoxins that cause the harmful effects of infectious diseases such as diphtheria and tetanus. It is proposed that this antigen, which is histamine-sensitizing, lymphocyte-leukocyte-promoting, and islets-activating (HSF-LPF-IAP), be designated pertussis toxin. Agglutinogen, hemagglutinin, and heat-labile (at 56 C) and heat-stable (at 100 C) toxins are no doubt interrelated with the immunologic and/or toxic reactions of whooping cough. It appears that the first defense against the disease is the antibody that prevents adhesion of the bacteria to the cilia of the respiratory epithelium and that the second defense is the antitoxin against pertussis toxin (HSF-LPF-IAP).

 

 Those who have been vaccinated are still considered susceptible, unless they have had a natural case of Pertussis, because a natural case can protect them at a higher rate than the vaccine. A vaccine may give them a less severe case with exposure, but it has been shown repeatedly that it does not prevent transmission. The vaccine for adolescents and adults is solely to prevent them from getting a clinical case and passing it on the infant. But overall, it just extends the length of time before they do/can get it.

The vaccine can provide some ‘herd immunity’. How? It can postpone, suppress the disease, or make a less severe case. But herd immunity is limited. The chance of catching pertussis at some point in ones life is inevitable. People can also get Pertussis more than once. This natural cycle of the disease also provides herd immunity. Pertussis has virulent cycles of every 2-5 years and vaccines have not changed its natural virulence cycle.

 Underreporting of Pertussis has been acknowledged repeatedly. How does this correlate to the reduced disease burden? Simply put-It is only a guess.

Reemergence of Pertussis: Methods

 

Data from pertussis reporting (required by law since 1976) were obtained from 1976 to 1998 from the Inspectorate of Health. A case definition, introduced in 1988, included clinical symptoms and laboratory confirmation (or close contact with a person with laboratory-confirmed pertussis).

…From 1988 to April 1997, laboratory confirmation was defined as either a positive culture of B. pertussis (or B. parapertussis) or positive two-point serology, in turn defined as a significant rise of immunoglobulin (Ig) G antibodies against pertussis toxin or IgA antibodies against B. pertussis in paired sera. In April 1997, a positive polymerase chain reaction (PCR) and positive one-point serology were also accepted as laboratory confirmation. Positive one-point serology was defined as high IgG or IgA antibody titers in a single serum sample…

 

 Pertussis in Adults

 …In the prevaccine era, reported pertussis was a cyclic disease, with epidemic peaks every 2 to 5 years [9]. When pertussis was brought under control by vaccination of children in the 1960s in the United States and England and Wales, it was noted that the 2– to 5-year cyclic pattern continuedFailure of the pertussis cycle to lengthen led to Fine and Clarkson’s suggestion [11] that immunization controlled the disease in children but did not disrupt circulation of the organism. This observation and the knowledge that adults were a common source of disease in infants led our group and others to study the epidemiology of adult pertussis.

…contrast with our findings in the UCLA students (94% of whom had been vaccinated in childhood), we found that German adults (most of whom had not been vaccinated during childhood) were more likely to have typical pertussis with whooping and post-tussive vomiting [12]. Twenty-six percent of these adults had had pertussis during childhood.

Immunoglobulin A antibodies to B. pertussis antigens usually result from infection, not immunization. With this fact in mind, we examined the prevalence and degree of IgA antibody to four B. pertussis antigens in young adults in the United States and Germany [18]. We found that the mean titers and the prevalence of antibody to the four antigens were similar, suggesting that the circulation of B. pertussis in adults in the two countries was similar even though pertussis was epidemic in Germany and rare in the United States. In another study [19], in which we obtained serum samples yearly for 5 years from 51 persons, 90% of these persons had serologic evidence of at least one case of pertussis [19].

 

Essential Problems in Pertussis (Am J Public Health, Apr 1939; 29: 337 – 340).

…It would seem reasonable to expect that the case fatality of pertussis might have been favorably affected bv the better home hygiene, antirachitic and other nutritional advances in the dietaries of children, more general and skilled home nursing of patients during isolation, and other factors which we see applied for the benefit of children under 5 years of age, but there are, I believe, no studies to confirm these general impressions.

 

…Second, one finds a very considerable incompleteness of reporting, the extent of which varies widely according to the interest and adequacy of the local health and medical services of the community, from approximate completeness to about 5 per cent of estimated cases.

Third, one finds that routine departmental procedure in establishing the diagnosis and recording the presumed susceptibility, exposure, and subsequent history of infection in households where other children than the reported patient are living, is neither uniform nor adequate to permit study of the relative merits of isolation periods of different lengths, of inoculations intended to prevent, or of therapy designed to modify the course of the disease.

 

 Pertussis surveillance

…Surveillance is carried out in some countries, but is not done in any meaningful way in three quarters of the world. Surveillance data and coverage data are both unreliable. Reliable surveillance data are needed to check coverage and vaccine efficacy; both surveillance and coverage data are needed to monitor immunization programmes…

… There are two principal methods of estimating burden: the natural history method and the proportional mortality method. The general approach used by WHO to estimate disease burden is to start with an expert consultative process in order to develop a sound approach. The methodology should aim to use the best data available and seek to validate results with existing data. Sensitivity analysis and continuous critical review are the only guarantees that the approach is as sound as it can be.

The estimates continue to be refined as new information becomes available. The final product is a database of cases and deaths by age, sex, country and year, as well as a careful documentation of methods, assumptions, and data sources. The process should result in recommendations on how to improve the precision, robustness and usefulness of the estimates.

Factors that affect the estimates are epidemiologic, demographic and programmatic, as well as co-factors such as HIV prevalence and nutritional status. Other practical issues include the quality and generalizability of the input data. Validation of the estimates is always important. The process is often messy since reliable data may be lacking, broad extrapolations or generalizations are made, or there is a heavy reliance on “expert opinion”.

 

 Prevention of Pertussis among Adolescents by Vaccination: Taking Action on What We Know and Acknowledging What We Do Not Know

…But there is much that is not known about pertussis. It is unclear whether the recent increases in reported disease are real or are artifacts of increased recognition; the increase in reported cases among young infants, coupled with relatively stable rates of reported disease among older infants and preschool-aged children, suggests that there may be a real increase in the circulation of Bordetella pertussis in some age groups [1]. But there is no doubt that ascertainment of pertussis is variable and incomplete in most age groups. Physicians may not consider the diagnosis, especially in adolescents and adults, because of a lack of clinical awareness that pertussis occurs in these age groups. Diagnostic testing is imperfect, and some tests have not been well standardized. Culture of B. pertussis remains the gold standard by which other assays are judged, but unless the diagnosis is considered early in the course of illness and before administration of antimicrobial therapy, isolation of the bacterium is unlikely. Serological testing, once standardized, may facilitate diagnosis, but it remains unavailable in most areas, and assays based on PCR are variable in sensitivity and specificity [2]. Thus, our knowledge of the burden of pertussis is far from complete.

There is also much that we do not know about the dynamics of B. pertussis transmission. It is unclear what impact vaccinating young adolescents would have on disease incidence in other age groups. Do middle and high schools, with their high contact rates and susceptible populations, amplify B. pertussis circulation in the community? If routine vaccination of young adolescents prevented those outbreaks but immunity was not long lasting, would outbreaks then occur among young adults? Would transmission to young infants—the group with the highest morbidity and mortality due to pertussis—decrease or increase following implementation of an adolescent pertussis vaccination program? Mathematical modeling suggests that the impact of routine adult pertussis vaccination on the incidence of pertussis in young children may be relatively modest [3].

Because of these and other uncertainties, estimating the impact of pertussis vaccination of adolescents and adults on disease burden requires many assumptions….

 

Epidemiology of pertussis

 

 …In the majority of countries where pertussis is a notifiable disease, a case-based national surveillance system is in place. However, different case definitions, methods of diagnosis and reporting and surveillance systems make direct intercountry comparisons difficult, and pertussis is not a statutory notifiable disease in every country. Nevertheless the general consensus is that reported incidences are probably considerably lower than the actual incidence of pertussis; underreporting is common. Prolonged cough may be the only clinical feature in adolescents or adults, who may present for diagnosis late (precluding laboratory confirmation) or not at all. When they do present, their condition is often misdiagnosed because, in part, clinicians continue to perceive pertussis as a childhood disease.Despite underreporting, an increased incidence of infant, adolescent and adult pertussis has been observed worldwide since the introduction of widespread vaccination… 

 

 Also See:  Failure of Physicians to Consider the Diagnosis of Pertussis in Children

  

More on Adacel (11-64 years):

 Clinical Studies;

 

The efficacy of the tetanus toxoid and diphtheria toxoid used in Adacel vaccine was based on the immune response to these antigens compared to a US licensed Tetanus and Diphtheria Toxoids Adsorbed For Adult Use (Td) vaccine manufactured by Sanofi Pasteur Inc., Swiftwater, PA.

The protective efficacy against mild pertussis (defined as at least one day of cough with laboratory-confirmed B pertussis infection) was 77.9% (95% CI: 72.6%, 82.2%). (8) (9) In addition, the ability of Adacel vaccine to elicit a booster response to the pertussis antigens following vaccination was evaluated. The acellular pertussis formulations for Adacel and DAPTACEL vaccines differ only in the amount of detoxified PT (2.5 μg in Adacel vaccine versus 10 μg in DAPTACEL vaccine).

The primary measures of immunogenicity were (a) the percentage of participants attaining an antibody level of at least 0.1 IU/mL and (b) the percentage of participants achieving a rise in antibody concentration after vaccination (booster response). The demonstration of a booster response depended on the antibody concentration to each antigen prior to immunization.

 Threshold or “cut-off” values for antibody concentrations to each antigen were established based on the 95th percentile of the pre-vaccination antibody concentrations observed in previous clinical trials. A booster response was defined as a four-fold rise in antibody concentration if the pre-vaccination concentration was equal to or below the cut-off value and a two-fold rise in antibody concentration if the pre-vaccination concentration was above the cut-off value.

 The efficacy of the pertussis antigens used in Adacel vaccine was inferred based on a comparison of pertussis antibody levels achieved in recipients of a single booster dose of Adacel vaccine with those obtained in infants after three doses of DAPTACEL vaccine. In the Sweden I Efficacy Trial, three doses of DAPTACEL vaccine were shown to confer a protective efficacy of 84.9% (95% CI: 80.1%, 88.6%) against WHO defined pertussis (21 days of paroxysmal cough with laboratory-confirmed B pertussis infection or epidemiological link to a confirmed case).

 …Pregnancy Category C

 

Animal reproduction studies have not been conducted with Adacel vaccine. It is also not known whether Adacel vaccine can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Adacel vaccine should be given to a pregnant woman only if clearly needed…

Nursing Mothers

 

It is not known whether Adacel vaccine is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Adacel vaccine is given to a nursing woman.

The safety and effectiveness of concomitant administration of Adacel vaccine with other vaccines has not been evaluated.

  

 Boostrix (10-18years)

 Prevention of Pertussis, Tetanus, and Diphtheria Among Pregnant and Postpartum Women and Their Infants

In 2006, ACIP recommended routine administration of Tdap for postpartum women who were not vaccinated previously with Tdap to provide personal protection and reduce the risk for transmitting pertussis to their infants (1,2) . After careful consideration, in June 2006, ACIP voted to reaffirm its recommendation for use of Td in pregnant women who have urgent indication for tetanus toxoid or diphtheria toxoid vaccination to prevent maternal or neonatal tetanus, or to prevent diphtheria. Pregnant women not vaccinated previously with Tdap will receive a measure of protection against pertussis by ensuring that children in the household are up-to-date with recommended doses of pediatric diphtheria and tetanus toxoids and acellular pertussis vaccine (DTaP)* (2123) and that adult and adolescent household contacts have received a dose of Tdap (Table 2) (1,2). Health-care providers can monitor pregnant women who have not received a dose of Tdap for exposures to pertussis or to respiratory illness consistent with pertussis, and they can administer antimicrobials for postexposure prophylaxis or treatment of pertussis, if needed, to reduce the risk for transmitting pertussis to their infants.

This report provides the background and rationale for routine administration of Tdap in postpartum women who were not vaccinated previously with Tdap and for maintaining the previous recommendation for use of Td in pregnant women if indicated. The safety and efficacy of using Tdap in pregnant women has not been demonstrated, and Tdap is not recommended for use in pregnant women in any country. No evidence exists of excess morbidity or any fatality among pregnant women ascribed to pertussis. No evidence exists demonstrating whether

  • Tdap in pregnant women harms the fetus or increases risk for adverse pregnancy outcomes,
  • transplacental antibody induced by Tdap administered during pregnancy will protect infants against pertussis, or
  • Tdap-induced transplacental maternal antibody will have a negative impact on an infant’s protective immune response to later-administered routine pediatric DTaP or to conjugate vaccines containing tetanus toxoid or diphtheria toxoid.

Health-care providers should weigh the theoretical risks and benefits before choosing to administer Tdap vaccine to a pregnant woman…

…The specific issues for pertussis differ from those for tetanus and diphtheria. Important among these is the limited understanding of immunity and correlates of protection for pertussis. In addition, data supporting the safety of vaccinating pregnant women with Tdap to prevent pertussis are scarce for women, their fetuses, and pregnancy outcomes. Whether transplacental maternal antibody exerts an inhibitory or other effect on the infant-protective immune response to active immunization with pediatric DTaP or conjugate vaccines containing tetanus toxoid or diphtheria toxoid has not been studied. Protection against infant pertussis through Tdap-induced transplacental maternal antibody has not been demonstrated. Until additional information is available, the majority view of the working group held that Tdap administered to women in the immediate postpartum period, in addition to ensuring pertussis vaccination of close contacts, would likely provide a measure of protection for mother and infant.

 

Vaccinating Pregnant Women against Pertussis

Tdap:

No prelicensure studies were conducted with Tdap in pregnant women. In 2005, to increase understanding of the safety of Tdap in relationship to pregnancy, both Tdap manufacturers established registries to solicit voluntary reports of pregnant women who received Tdap during pregnancy or who received Tdap and were determined subsequently to be pregnant (212,213). The main utility of the registries is to signal the possibility and nature of any risk (214). All women who are vaccinated with Tdap at any time during pregnancy should be reported to the registry as early as possible during the pregnancy. Information from pregnancy registries differs from surveillance reports, which are used to evaluate outcomes among women when an adverse outcome of pregnancy already might have occurred (e.g., an infant born with a birth defect) (214).

Also see: Guidelines for Vaccinating Pregnant Women (ACIP Guidelines May 2008) 

  • Pregnancy is not a contraindication for use of Tdap. Data on safety, immunogenicity and the outcomes of pregnancy are not available for pregnant women who receive Tdap. When Tdap is administered during pregnancy, transplacental maternal antibodies might protect the infant against pertussis in early life. They also could interfere with the infant’s immune response to infant doses of DTaP, and leave the infant less well protected against pertussis. 11
  • ACIP recommends Td when tetanus and diphtheria protection is required during pregnancy. In some situations*, healthcare providers can choose to administer Tdap instead of Td to add protection against pertussis. When Td or Tdap is administered during pregnancy, the second or third trimester is preferred. 11
  • Providers who choose to administer Tdap to pregnant women should discuss the lack of data with the pregnant women and are encouraged to report Tdap administrations regardless of the trimester, to the appropriate manufacturer’s pregnancy registry: for Boostrix® to GlaxoSmithKline Biologicals at 1-888-825-5249, or for Adacel®, to sanofi pasteur at 800-822-2463. 11
  •  

    It appears there is much they ‘don’t know’. But that isn’t stopping them. Vaccinating Post-partum Mothers before leaving the hospital with Tdap, even if they are breastfeeding, has been increasing.

    Investigators in Houston have successfully implemented a novel vaccination strategy – vaccinating women who have just given birth to prevent them transmitting pertussis (whooping cough) to their young infants.  This study took place in a medically underserved and underinsured population.   Study investigators gave tetanus, diphtheria and acellular pertussis (Tdap) vaccine to over 1000 mothers at Ben Taub General Hospital, a county hospital that serves a predominantly Hispanic population in Houston, over a 3 month period.  Approximately 75% of women who were offered Tdap received the vaccine and when Tdap was not administered it was usually because mothers had received a recent tetanus vaccine (a relative precaution to receiving Tdap vaccine).  This program is, to our knowledge, the first to implement and track on a large scale the 2006 Centers for Disease Control and Prevention (CDC) recommendation that women receive Tdap before they leave the hospital after delivery.

    Also see: Forrest General gives recommended vaccine for new mothers

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    Whooping cough vaccine not as powerful as thought

    Whooping cough vaccine not as powerful as thought

     

    …Of the 18 students in the recent Cobb cluster, 17 were properly immunized with five doses of DTaP vaccine, which protects against diphtheria, tetanus and pertussis, health officials said.

     

    …But scientists are struggling to understand why reports of pertussis cases have risen dramatically since the 1980s. It may reflect more testing or diagnosis; it may reflect the cyclical nature of the disease. It’s even unclear how often clusters like the one in Cobb occur.

     

    About 10,000 cases and 20 infant deaths were reported in the United States last year, but some studies have suggested the number of people sickened each year may be closer to 300,000, CDC officials said.

    Experts believe the disease is underdiagnosed and underreported in vaccinated school-age children and adults who often have milder symptoms and whose childhood shots have worn off. They believe that adolescents and adults are spreading the disease to vulnerable infants and children.

     

    …While no vaccine is 100 percent effective, some parents are surprised and angry that a vaccine they trusted is failing to protect some children. And officials with the Georgia Division of Public Health said too many local doctors are not aware the disease is circulating in the community and can infect fully vaccinated children.

     

    Nationally, school-age children diagnosed with the disease are generally teenagers, which is what prompted a CDC advisory panel in 2005 to recommend an additional pertussis booster shot at age 11 or 12.

    To try to determine the magnitude of the problem at the four Cobb schools, last month CDC and local health officials gave voluntary pertussis tests to 108 children and staff who were currently coughing, and 22 of them showed evidence of recent infection, said Julie Gabel, a state health department epidemiologist.

    Despite the study’s test results, some doctors refused to believe parents when they said that their children had pertussis. “More than one said to the parent: ‘Well, your child couldn’t have had pertussis, your child’s been vaccinated,” Gabel said, adding that the department is working to educate physicians.

    At the four schools, health officials think the outbreaks are over or winding down. But whooping cough continues to be reported elsewhere. Georgia health officials aren’t aware of any other current whooping cough clusters.

    …“The real issue is what the rate of vaccine failure is,” said Orenstein, a former CDC official who recently became deputy director for vaccine preventable diseases at the Gates Foundation in Seattle…

     

    PERTUSSIS CASES

    U.S.

    2009* 1,699

    2008 10,007

    2007 10,454

    2006 15,631

    2005 25,617

    2004 25,827

    2003 11,647

     

    * Year so far

    Source: CDC

    Treatment of Pertussis

    Vaccinating yourself and your children will not prevent your new baby from getting it. The vaccine has one of the lowest efficacy rates and you can still spread the germs that cause it even if you are not currently infected. Pertussis isn’t as deadly for infants as you are led to believe it is. When they say the mortality rate for pertussis in infants under 6 months is 0.5%, or 1 out of every 200, that is including all the infants who are formula fed, who live with smokers, who have health problems, etc. There’s a big difference between a baby in those circumstances and a breastfed baby living in a healthy environment.

    Vitamin C in the treatment of Pertussis:

     Vitamin C, Infectious Diseases, & Toxins by Thomas E. Levy, MD, JD

    pg. 116: Otani (1936) found that pertussis bacteria seemed to be especially susceptible to the effects of vitamin C in the test tube, with high enough dose having a killing, bactericidal effect. It was also demonstrated that a culture of pertussis bacteria in which vitamin C had been added possessed a “strongly reduced” infectivity in test animals.

     

    Pg. 118: The bacteria causing pertussis can be killed in culture by vitamin C, and the effects of the pertussis toxin also appear to be lessened by vitamin C…

    …adequate regular dosing of vitamin C should prevent pertussis from ever being contracted.

     

     

    The primary function of Vitamin C is not to kill the bacteria. It does inhibit them, but the main action in any toxin-mediated disease is to neutralize the toxin, and to support the liver so that when the liver is reducing the amount of endotoxin,  the liver works much more efficiently.   It does not stop the disease. It modifies it, and makes the cough milder.

     

     Vitamin C also puts petrol into the tank of macrophages and phagocytes, and in vitro increases their activity levels. Therefore, in the body, it should increase the effectiveness of the immune system in general, as well as dealing with the specifics of the toxin issue, and inhibiting the bacteria itself.

    You can dissolve Vitamin C (sodium ascorbate powder) in breast milk. You can use a dropper or dribble it into the inside of the cheek. Don’t squirt it in their mouths in case they inhale it and that would trigger the vagus nerve.

     

    The Bowl tolerance Method:

     

    You give your child a small dose (1/4 tsp) of the C in liquid you choose every half hour to an hour until they have a loose stool. The amount of Vitamin C it took them to get there is just past tolerance. You then cut back 1/4 tsp and that’s saturation. Each person has a different level. Everyone will tolerate more when we are sick.

     

     For Breast feeding Mothers:

     

    It takes about 8 hours for the vitamin C you take to get through to the breast milk. A Pinch is about 250 mg. If I thought my child was really sick, then I would calculate Vitamin C for her at 375 mg/kg of body weight, and give that over waking hours, and perhaps a larger dose given just before bedtime.

     

     Also, a good vitamin and mineral supplement to help your body deal with emotional stress, Halibut Liver oil, and about 10 grams of vitamin C spread out over your waking hours. You can use powdered sodium ascorbate, and mix it (10 grams = 2 heaped teaspoons) in with 1.25 liters of water in a water bottle. Drink it gradually throughout the day.

     

    The Progression:

     

     First they get a cold. Then after a week, they start the odd cough, and after about two weeks, the cough gets stronger. At the end of the cough, which might be a month later, they will bring up globs of fairly thick mucus. This is because it pools down to the bottom of the lungs because the toxin from the bacteria has cut off most of the hairs in the bronchial that sweeps the mucus up and around. The cough sounds dry and that’s because the mucus membranes aren’t being kept as moist as they normally are. Most children, as long as they are getting that mucus up, and do not pool it (where secondary bacterial infections can set it) only have problems when they are coughing. The rest of the time they act normal. Coughing can be provoked by touching the back of the tongue, eating food, or running around. Towards the end of the illness, if they get worked up and tense up, it triggers the cough.

     

     To help a baby during the cough:

     

    Turn the baby round, with its back to yours. Split your legs, so the baby is supported around the tummy but the legs are straight down. Your hands make a net around the baby’s ribcage and tummy, and when the baby coughs, lean forward slightly and use the hands as a very gentle net so that the baby has something for the tummy to push against. They haven’t learned to control their abdominal muscles to get an efficient cough yet, so t hands make it much easier for them. If it is whooping cough, then you will get a thick clear mucus glob ejected. If it is whooping cough, then the cough will become more regular.

     

    The cough is caused by the bacteria adhering to the bronchial walls, and secreting a toxin, which cuts off the cilia (hairs) in the bronchials. These hairs sweep the mucus up and spread throughout the throat. The bronchial hairs move the mucus around all the time, so that it replaces, and at the same time, gets rid of any pathogens. This mucus is part of the innate immune system. It is linked to the BALT (Bronchial associated lymphatic tissue). You must keep the mucus moving. Whooping cough cuts off the hairs, and tries to stops the mucus from  moving. As long as you keep the mucus moving, your baby should not get a secondary infection.

    The other thing the toxin can do is get into the blood-stream, and irritate the body. If the baby’s immune system is not good then this toxin can get to the brain as well. If the mucus is not gotten out, bacteria will grow and cause a secondary bacterial infection, which they will want to treat with antibiotics. Whooping cough in rare cases can cause long-lasting bronchial problems. However, that is if you treat it the way the doctors do, with antibiotics. Antibiotics do not deal with the pooling mucus, or manage it, or deal with the toxin. If you keep the mucus moving there should be nor further problems other than the cough itself.

    Whooping cough will last approximately 100 days, but mainly as an irritating annoyance only. After a bout of whooping cough, for the next 6 – 9 months, any cold that the child gets, the child will start to whoop, or cough, the same way as they did with whooping cough. The reason for that is that it takes a long time for the hairs to grow back, and so any infection without proper hairs in the bronchials, will result in mucus pooling.
    It is this mucus pooling that has to trigger a cough strong enough, to get the mucus from the bottom of the bronchials up to the top. If they are coughing until they are purple, then your doses of vitamin C are too small. Bump them right up to the level of 375 milligrams per kilo of body weight over the waking hours, as a starting dose. If your dose is right, within 8 hours there should be a two third reduction in the coughing.

     

    Testing for Pertussis:

     This one is useless:

    Isolation of B. pertussis by culture is 100% specific; however, sensitivity of culture varies because fastidious growth requirements make it difficult to transport and isolate the organism. Although the sensitivity of culture can reach 80%–90% under optimal conditions, in practice, sensitivity typically ranges from 30%–60% (57). The yield of B. pertussis from culture declines in specimens taken after 2 or more weeks of cough illness, after antimicrobial treatment, or after previous pertussis vaccination (58). Within 3 weeks after onset of cough, culture is only 1%–3% sensitive (59). Although B. pertussis can be isolated in culture as early as 72 hours after plating, it takes 1–2 weeks before a culture result can definitively be called negative (60). Culture is essential to isolate B. pertussis for antimicrobial susceptibility testing and for molecular subtyping of strains.  
     
    Direct fluorescent antibody (DFA) tests provide rapid results (hours), but are generally less sensitive (sensitivity: 10%–50%) than culture. With use of monoclonal reagents, the specificity of DFA should generally be >90%; however, the interpretation of the test is subjective, and interpretation by an inexperienced microbiologist can result in lower specificity (61). Because of the limitations of DFA testing, CDC does not recommend its use.

     

    The only Pertussis diagnostic tests that the CDC endorses are culture and Nasophyngeal PCR. Tests other than the PCR have a high false positive or false negative rating. However, many medical articles still say that there are no reliable correlates of protection (antibody test) for Pertussis.

     

    Whooping cough cannot be correctly diagnosed without a nasopharyngeal swab because other pathogens like adenovirus can cause an identical syndrome, as can other bacteria, so the swab must be tested with the PCR (polymerase chain reaction) test.  

     
    Doctors will give you Erythromycin, which does not shorten, or do anything to lessen the course of the disease. It can make babies irritable, bother the stomach, and suppress the immune system further. It can simply make the situation worse. There is no reason to use antibiotics, unless the mucus they spit up becomes green in color. Make sure the child drinks enough liquids, to keep the mucus as thin and easy to get up as possible.

     

     

    Pertussis-Epidemiology and Transmission of Disease

    Epidemiology and Transmission of Disease

    Pertussis infection is unique to humans. There are no animal reservoirs, and the organism cannot survive for a prolonged period in the environment. Localized to the respiratory tract, the organism is transmitted primarily by aerosol droplets from an infected person to a susceptible one. The infection is highly contagious, with attack rates ranging from 50% to 100%. The highest attack rates occur among persons with exposure within 5 feet of a coughing patient.[5]

    In the pre-vaccine era, pertussis was predominantly an infection of children aged 1 to 5 years, with maternal immunity providing passive protection during an infant’s first year of life. At that time, an average of 175,000 US cases were reported per year (incidence of approximately 150 cases per 100,000 population).[6] The incidence of disease declined steadily over the two decades after introduction of whole-cell pertussis vaccine, reaching an all-time low of just over 1000 reported cases in 1976.[7,8] Since then, the incidence of infection has continued to rise, with almost 26,000 cases reported to the CDC in 2004 (Figure 1).[9]

     

     Pertussis is the only vaccine-preventable disease on the rise in the US and it is severely underreported. CDC estimates that, at best, one-third of cases are believed to be reported to the CDC;[10] other estimates place the reported cases at 1 in 10 to 1 in 20 of the true incidence.[11] Although pertussis incidence remains highest among young infants, rates are also on the rise in adolescents and adults and there may be significant under-reporting in these age groups, especially those with mild or atypical infection.[7] Compared with surveillance data from 1994 to 1996, the pertussis incidence rate among adolescents and adults increased 62% and 60%, respectively, from 1997 to 2000.[7]

    Increased incidence of pertussis in adolescents and adults relates to waning immunity and, likely, to a combination of previous underreporting and recent improvements in reporting processes. The longer the duration since vaccination, the higher the attack rate (Figure 2).[12] Data from a seroprevalence study by Cattaneo et al showed a peak in antibody titers at 4 to 6 years of age, coinciding with DTaP booster dosing, followed by a decline, and a second peak between 13 and 17 years of age.[13] Similar findings were documented by the National Health and Nutrition Examination Survey (NHANES), which reported a protracted decline interrupted by a peak in persons aged 40 to 45 years.[14] Since no pertussis-containing vaccine had been given past the age of 6 years, these spikes in adolescents and older persons clearly represent natural pertussis exposure. These persons not only represent potential cases, but a reservoir of disease that puts those most susceptible to significant morbidity and mortality (ie, those at the extremes of age) at risk of exposure.

    Pertussis has been estimated to account for up to 17% of prolonged cough illness in adults.[15,16] Among adults with cough illness, the incidence of confirmed pertussis has been estimated at 170 to 630 cases per 100,000.[17,18] The rates among adolescents were almost 2-fold higher. Data from a prospective acellular pertussis vaccine efficacy trial (APERT) extrapolate the burden of pertussis to be nearly 1 million US cases annually in persons 15 years old.[11]

    Given the large disease burden in adolescents and adults estimated by these studies, the limited number of confirmed cases of pertussis (defined in Table 1 ) in older children, adolescents, and adults is striking. A large proportion of these cases may be atypical and undiagnosed. However, according to recent data from Bisgard et al,[19] in cases where the source of pertussis was identifiable, adolescents and adults were the primary source of infection for 20% and 56%, respectively, of infants with pertussis.

    Contact with infected adolescents and adults is a common source of B. pertussis infection in infants and unprotected, young children. Widespread silent transmission of pertussis within families has been reported.[20] In a study of risk factors for pertussis-related hospitalizations, siblings were the most common source (53%), followed by parents (20%), other relatives (12%), neighbors (8%), and day-care contacts (3%).[21] In a case-control study, infants of adolescent mothers (aged 15 to 19 years) were 6-fold more likely to contract pertussis, compared with infants of older mothers (aged 20 to 29 years).[22]

    Details of the pathogenesis of pertussis infection have been extensively reviewed elsewhere.[23] In brief, the development of pertussis infection begins with entry of B. pertussis into the respiratory tract of a susceptible host. The organism produces adhesion and bacterial surface attachment factors that allow its attachment to cilia in the respiratory mucosa. Tracheal cytotoxin and other toxins are produced and released into the local environment, damaging the cilia and respiratory epithelium. These changes disturb clearance of pulmonary secretions and probably result in development of the coryza and cough observed during the catarrhal phase of the illness. Even as local damage increases, attracting host immune cells, the actions of additional toxins probably inhibit phagocyte functions, thereby protecting the proliferating organisms from clearance. In some cases, the proliferation of B. pertussis continues until organisms reach the alveoli, resulting in pneumonia.

    Pertussis symptoms are nonspecific in nature, making the clinical diagnosis challenging. The type and severity of symptoms that develop are highly variable, as is the time frame over which they appear and resolve. Adolescents and adults, as well as those partially protected by pertussis vaccine, frequently have mild clinical disease (or even asymptomatic disease) that goes undiagnosed. Although illness may be milder in adolescents and adults, they are a reservoir of infection and may transmit whooping cough to unimmunized or partially immunized infants. Of great concern, health care providers often do not recognize the varied clinical presentations and do not consider a pertussis diagnosis in patients with chronic cough.[17] Furthermore, management of pertussis is complicated by the fact that infected persons are most contagious early in their illness, before they become symptomatic.

    Despite significant interpatient variability, generalizations can be made about the clinical course of illness ( Table 2 ).[5,24] Pertussis infection develops in four sequential stages, beginning with an incubation period during which infected individuals are asymptomatic followed by three stages of symptomatic illness. The incubation period of pertussis infection commonly lasts for 7 to 10 days, but can be as short as 4 days or as long as 21 days. The first stage in which symptoms can be observed is the catarrhal stage. This stage, which typically lasts 1 to 2 weeks, is characterized by the insidious onset of coryza, sneezing, low-grade fever, and a mild, occasional, nonspecific cough that gradually becomes more severe. In young infants, this stage is often characterized by excessive sneezing or “throat clearing.”

    During the next stage, the paroxysmal stage, many pertussis patients have bursts, or paroxysms, of numerous, rapid coughs, apparently due to impaired mucociliary clearance. At the end of the paroxysm, a long inspiratory effort is oftentimes associated with a high-pitched whoop. Post-tussive vomiting and cyanosis can also occur. The paroxysmal attacks increase in frequency during the first 1 to 2 weeks, remain at the same level for 2 to 3 weeks, and then gradually decrease.

    During the convalescent stage, which lasts for weeks to months, recovery is gradual, with cough becoming less paroxysmal and then disappearing.

    The symptomatology of infants during the paroxysmal stage of infection is different from that in adolescents and adults. Although very young infants do experience paroxysms of coughing, they often do not “whoop.” Although the absent whoop in adolescents and adults is usually associated with milder disease, the whoop may be absent in infants because they lack sufficient musculature in the chest wall to take the deep inhalation that creates the whooping sound. The whoop may appear later in the disease as infants gain in size and strength. Infants may also exhibit clinical symptoms such as gagging, gasping, or eye bulging. Occasionally, they may also present with bradycardia or cyanosis. Pertussis is often ignored in the differential diagnosis of cough illness in young infants due to the absence of a “whoop” and the frequency of concomitant respiratory infections.

    Life-threatening complications are most common in infants <3 months of age,[19,21] but infection can also be severe in some adult cases. Secondary bacterial pneumonia is diagnosed in up to one quarter of young infants with pertussis[21,25] and is the most common complication and the cause of most pertussis-related deaths across age groups. Data from 1997 to 2000 indicate that pneumonia occurred in up to 5.2% of all reported pertussis cases, and 11.8% of infants <6 months of age.[7] Other complications include seizures (0.8% of all cases, 1.4% of infants <6 months of age) and encephalopathy (0.1% of all cases, 0.2% of infants <6 months of age).

    Death due to pertussis is rare (0.2%). The vast majority (90%) occurs in children younger than 6 months of age with no predisposing conditions.[2] Risk factors for death among infants include premature birth, Hispanic ethnicity, and having a young mother.[2,26] Pertussis has also been linked to sudden infant death (3% to 5%).[27,28] Other less severe complications in infants include otitis media, anorexia, and dehydration. Pressure effects of severe paroxysms may lead to pneumothorax, epistaxis, subdural hematomas, hernias, and rectal prolapse. Additional complications identified in adolescents and adults include urinary incontinence, rib fracture, unilateral hearing loss, herniated disk, and precipitation of angina pectoris.[5,24]

    Laboratory confirmation of pertussis infection is not as straightforward as that of many other infectious diseases. Most local laboratories are not equipped to make the diagnosis of B. pertussis infection. The preferred approach is polymerase chain reaction (PCR) testing and a culture of the organism from a posterior nasopharyngeal specimen obtained using two separate Dacron swabs.[29] For proper collection, the swab must touch the epithelial cells of the posterior nasopharyngeal wall. Culture is the only method from which antibiotic susceptibilities can be measured and molecular typing determined. Isolation of the organism is compromised by recent antibiotic therapy effective against pertussis (ie, macrolide/azalide or trimethoprim-sulfamethoxazole), by delay in specimen collection beyond the first 2 weeks of illness, and in vaccinated persons.

    Serologic testing for B. pertussis is limited by a lack of standardization and should not be obtained for clinical decision making.[30] However, because of its convenience, serology continues to be the most common method used to diagnosis pertussis, especially in the later stages of the infection, making it an important tool in our understanding of disease frequency.[31] Various enzyme-linked immunosorbent assay (ELISA) techniques are available in commercial laboratories, although there is little evidence of sensitivity or specificity relative to clinical infection.[32] None of the commercially available serologic tests for pertussis is FDA-licensed for the routine diagnosis of infection.[14] Direct fluorescent antibody (DFA) is no longer considered useful for diagnosis of pertussis due to low sensitivity and variable specificity.

    Pertussis Vaccination of Children

    DTaP vaccine, which contains purified, inactivated components of B. pertussis cells (along with tetanus and diphtheria toxoids), has been available in the United States for more than a decade. Since 1997, the CDC recommends DTaP for all doses of the vaccination series for infants and children <7 years of age. The primary immunization series consists of three doses given at 4- to 8-week intervals, beginning at 6 weeks to 2 months of age. A fourth dose is given 6 to 12 months after the third dose. Children who have received all four primary doses before the fourth birthday should receive a fifth (booster) dose before entering school. A fifth dose is not necessary if the fourth dose was administered on or after the fourth birthday.

    Point estimates of vaccine efficacy across trials of infants ranged from 80% to 85%.[24] In comparative studies, the acellular pertussis vaccine was significantly more effective than the whole-cell DTP, which is no longer available in the United States. Local and systemic adverse reactions occurred less frequently among infants vaccinated with acellular pertussis vaccine than among those vaccinated with whole-cell pertussis.[34]

    Pertussis Vaccination of Adolescents and Adults

    The availability of a less reactogenic acellular pertussis vaccine combined with evidence of substantial pertussis infection among adolescents and adults led to reconsideration for the need for acellular pertussis boosters among older subgroups.

    Specific formulations of Tdap for adolescents 10 to 18 years, Boostrix® (GlaxoSmithKline), and for adolescents and adults 11 to 64 years, Adacel® (sanofi pasteur), were recently licensed for use in the United States. They contain tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis. In a randomized, controlled, multicenter clinical trial, 10- to 18-year-olds were vaccinated with one dose of Boostrix or a US-licensed Td vaccine.[35] Each subject had completed his or her routine childhood vaccinations against diphtheria, tetanus, and pertussis according to the CDC recommended schedule. Boostrix was comparable to the Td vaccine based on immunogenicity. In both treatment groups, >99.9% of subjects had anti-diphtheria and anti-tetanus concentrations greater than 0.1 IU/mL, indicating seroprotection against these two diseases. In the Boostrix treatment group, anti-pertussis antibodies levels following primary immunization exceeded (by 1.9 to 7.4 times) those observed in infants, in whom efficacy against pertussis disease was previously demonstrated. The overall safety profile was comparable between the Boostrix and Td vaccine groups.

    Adacel was evaluated in four principal clinical trials in which 7206 individuals (4185 adolescents and 3021 adults) who had not received tetanus or diphtheria toxoid-containing vaccines within 5 years were enrolled. The trials consisted of one randomized, controlled trial that compared Adacel vaccine to a licensed Td vaccine,[36] one lot consistency trial, and two concomitant administration trials (one with hepatitis B vaccine and one with influenza vaccine). Across trials, a total of 3393 adolescents and 2448 adults received Adacel vaccine and 792 adolescents and 573 adults received Td vaccine. In the largest Adacel trial, the seroprotection rate (of at least 0.1 IU/mL) for tetanus and diphtheria was 99.8% and 100%, respectively.[36] Pertussis antibody geometric mean titers (GMTs) following one dose of Adacel were 2.1- to 5.4-fold higher than those observed among infants following three doses of DTaP. Overall, Adacel vaccine was well tolerated, with local and systemic adverse reactions occurring at similar rates in the Adacel and Td vaccine groups. The ACIP recently revised its recommendations for pertussis vaccination. The immunization schedule now includes a Tdap booster dose for all adolescents at 11 to 12 years of age ( Table 3 ).[37,38] The ACIP also calls for catch-up vaccination of those aged 13 to 18 years who did not receive the Td booster. Finally, because of the importance of controlling pertussis, those in this age range who received the Td booster are encouraged to get the new Tdap vaccine after a suggested 5-year interval. This interval may be shortened to as little as 2 years in the presence of increased risk (eg, during outbreaks or periods of increased pertussis activity in the community).[7]

    The ACIP also recommends a single dose of Tdap booster to replace the next scheduled dose of tetanus diphtheria vaccine among persons 19 to 64 years of age. In addition, adults who have or who anticipate having close contact with a vulnerable infant (ie, an infant who has not received two to three doses of DTaP) should receive a single dose of Tdap booster.[39]

    In February 2006, the ACIP recommended a single dose of Tdap booster as soon as feasible for health care workers in hospital or ambulatory care settings who have direct patient contact. The Committee stated that priority should be given to vaccination of health care workers with direct contact with infants <12 months of age. Other health care workers should receive a single dose of Tdap booster according to the routine recommendation and interval guidance for use of Tdap among adults.[39]

    Widespread administration of Tdap vaccination should have a substantial impact on pertussis. By way of example, adolescent pertussis immunization programs were recently implemented countrywide in Canada, but started earlier in the Northwest Territories and Newfoundland. Following introduction of an adolescent booster dose, pertussis incidence in the Northwest Territories decreased from 7.9 per 100,000 in the late 1990s to 0.2 per 100,000 in 2004.[40] In Newfoundland, no person vaccinated with the Tdap booster has been diagnosed with pertussis to date.[41]

    Pertussis is an often serious, potentially deadly community-acquired illness in persons of all ages. Infected adolescents and adults may suffer substantial morbidity and also are a reservoir for disease transmission to infants. Newly available Tdap vaccines are safe and effective in preventing infection. The addition of a pertussis booster to the previously available tetanus and diphtheria booster will not only directly benefit vaccine recipients but may allow for greater control of the pertussis reservoir in adolescents and adults, potentially leading to decreased incidence in infants who are at highest risk for severe complications including death. If widely administered, Tdap vaccination should have a substantial impact on pertussis.

    Epidemiology and Transmission of Disease

    J Am Board Fam Med.  2006;19(6):603-611.  ©2006 American Board of Family Medicine.

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