Randomized Controlled Trial of the Safety and Immunogenicity of Revaccination With Tetanus-Diphtheria-Acellular Pertussis Vaccine (Tdap) in Adults 10 Years After a Previous Dose

A literature review and evidence-based evaluation of the Dutch national immunisation schedule yield possibilities for improvements

National Immunisation Programmes (NIPs) develop historically. Its performance (disease incidences, vaccination coverage) is monitored. Reviewing the schedule as a whole could inform on further optimisation of the programme, i.e., providing maximal protection with the lowest number of doses. We systematically evaluated the performance and strategies of the Dutch pathogen-specific NIP schedules through literature review, assessment of surveillance data and expert opinions. Pathogen-specific vaccinations were categorised according to their strategy of protection: I) elimination or eradication, II) herd immunity or III) 'only' individual protection. The schedule of each vaccine-component was evaluated based on fixed criteria: 1. Is the achieved protection adequate? 2. Is the intended protection achieved? 3. Does the programme include too many or too few doses? 4. Is the timing optimal or acceptable? and 5. Are there drawbacks of the NIP for (part of) the population? Identified issues were explored using surveillance data and literature. Using fixed criteria facilitated comparison between pathogens and revealed opportunities to optimise the Dutch NIP by: i. Reducing the number of polio and tetanus vaccinations; ii. prolonging the interval between diphtheria, pertussis, tetanus, polio, hepatitis B, and Hib vaccine doses for improved effectiveness; iii. Expedite the second measles vaccination from 9 to 2-4 years of age to offer unvaccinated children and primary vaccine failures an earlier chance to be protected; and iv. Delaying the second mumps vaccination to enhance protection in adolescents/young adults. No schedule adaptations were deemed necessary for the vaccines against HPV, rubella, pneumococcal disease, and meningococcal disease. Based on this evaluation the NITAG advised to move the DTaP-IPV-HBV-Hib-booster from age 11 to 12 months, the second MMR-dose from 9 to 2-4 years, replace the Tdap-IPV at 4 years with a Tdap at 5-6 years and move the dt-IPV from 9 to 14 years. Implementation of these changes is planned for 2025.

Overuse of tetanus toxoid vaccine: a common but under-addressed issue in Nepal

Introduction and importance

Tetanus, though potentially fatal, is preventable with proper vaccination, but high tetanus titers from frequent or higher doses can lead to increased adverse events. In countries like Nepal, where tetanus vaccines are readily available over the counter, irrational and frequent dosing, especially in certain occupational groups, is a noted issue.

Case presentation

A 28-year-old metal worker presented with a superficial cut on his forearm, managed with standard wound care, and reported a history of frequent tetanus vaccinations. Given his extensive vaccination history, a tetanus toxoid injection was deemed unnecessary, and he was educated on proper vaccination schedules and advised to seek medical attention for future injuries.

Clinical discussion

Timely administration of vaccines for pre-exposure and postexposure prophylaxis is crucial for combating tetanus, with booster doses recommended every 10 years or as needed for wound management. High antibody titers from frequent tetanus vaccinations can increase the risk of adverse events, prompting guidelines to avoid administering Td more frequently than every 10 years unless necessary. Local reactions, like pain and swelling at the injection site, are common, while systemic reactions can include fever and peripheral neuropathy. Over-immunization is a concern in some regions, with frequent unnecessary booster doses potentially causing harm and highlighting the need for adherence to vaccination guidelines.

Conclusion

Modifying and monitoring adult Td booster vaccination can lead to significant cost savings and fewer adverse events, requiring proper vaccination record-keeping, accurate assessment, and adherence to guidelines by healthcare workers.

Recommendations for Adult Immunization by the Korean Society of Infectious Diseases, 2023: Minor Revisions to the 3rd Edition

The Korean Society of Infectious Diseases has been regularly developing guidelines for adult immunization since 2007. In 2023, the guidelines for the following seven vaccines were revised: influenza, herpes zoster, pneumococcal, tetanus-diphtheria-pertussis (Tdap), human papillomavirus (HPV), meningococcal, and rabies vaccines. For the influenza vaccine, a recommendation for enhanced vaccines for the elderly was added. For the herpes zoster vaccine, a recommendation for the recombinant zoster vaccine was added. For the pneumococcal vaccine, the current status of the 15-valent pneumococcal conjugate vaccine and 20-valent PCV was described. For the Tdap vaccine, the possibility of using Tdap instead of tetanus-diphtheria vaccine was described. For the HPV vaccine, the expansion of the eligible age for vaccination was described. For the meningococcal vaccine, a recommendation for the meningococcal B vaccine was added. For the rabies vaccine, the number of pre-exposure prophylaxis doses was changed. This manuscript documents the summary and rationale of the revisions for the seven vaccines. For the vaccines not mentioned in this manuscript, the recommendations in the 3rd edition of the Vaccinations for Adults textbook shall remain in effect.

Immunogenicity at delivery after Tdap vaccination in successive pregnancies

Background

Tetanus, diphtheria, acellular pertussis (Tdap) vaccination is recommended to be administered in every pregnancy. Although the safety of this strategy has been confirmed, the immunogenicity of Tdap vaccination in two successive pregnancies has not yet been described. This study investigated Tdap-specific immunity levels and transplacental transfer in two successive pregnancies after repeated Tdap-vaccination.

Methods

Women enrolled in prior studies on Tdap vaccination during pregnancy were invited to participate in a follow-up study if they became pregnant again. Women who received a Tdap vaccine in both pregnancies were considered for this analysis. Tdap-specific total IgG and IgG subclasses were measured with a multiplex immunoassay.

Results

In total, 27 participants with a mean interval between deliveries of 2.4 years were included in the analysis. In maternal serum, Tdap-specific total IgG levels were comparable at both deliveries whereas in cord serum, all Tdap-specific total IgG antibody levels were reduced at the second compared to the first delivery. This was largely reflected in the IgG1 levels in maternal and cord serum. Transplacental transfer ratios of total IgG and IgG1 were also mostly reduced in the second compared to the first pregnancy.

Conclusion

This study reports for the first time Tdap-specific total IgG and IgG subclass levels and transfer ratios after repeated Tdap vaccination in successive pregnancies. We found reduced transfer of most Tdap-specific IgG and IgG1 antibodies in the successive pregnancy. As pertussis-specific antibodies wane quickly, Tdap vaccination in each pregnancy remains beneficial. However, more research is needed to understand the impact of closely spaced booster doses during pregnancy on early infant protection against pertussis.

Patient-reported reactogenicity and safety of COVID-19 vaccinations vs. comparator vaccinations: a comparative observational cohort study

BACKGROUND

In the course of the SARS-CoV-2 pandemic, multiple vaccines were developed. Little was known about reactogenicity and safety in comparison to established vaccines, e.g. influenza, pneumococcus, or herpes zoster. Therefore, the present study aimed to compare self-reported side effects in persons vaccinated against SARS-CoV-2 with the incidence of side effects in persons receiving one of the established vaccines.

METHODS

A longitudinal observational study was conducted over a total of 124 days using web-based surveys. Persons receiving either a vaccination against SARS-CoV-2 or one of the established vaccines (comparator group) were included. In the first questionnaire (short-term survey), 2 weeks after vaccination, mainly local and systemic complaints were evaluated. The long-term survey (42 days after vaccination) and follow-up survey (124 weeks after vaccination) focused on medical consultations for any reason. Multivariate analyses were conducted to determine the influence of the vaccine type (SARS-CoV-2 vs. comparator) and demographic factors.

RESULTS

In total, data from 16,636 participants were included. Self-reported reactogenicity was lowest in the comparator group (53.2%) and highest in the ChAdOx1 group (85.3%). Local reactions were reported most frequently after mRNA-1273 (73.9%) and systemic reactions mainly after vector-based vaccines (79.8%). Almost all SARS-CoV-2 vaccines showed increased odds of reporting local or systemic reactions. Approximately equal proportions of participants reported medical consultations. None in the comparator group suspected a link to vaccination, while this was true for just over one in 10 in the mRNA-1273 group. The multivariate analysis showed that people with SARS-CoV-2 vaccination were not more likely to report medical consultations; patients who had received a regimen with at least one ChAdOx1 were even less likely to report medical consultations. Younger age, female gender and higher comorbidity were mostly associated with higher odds of medical consultations.

CONCLUSION

The rate of adverse reactions after established vaccinations was roughly comparable to previous studies. Two weeks after vaccination, participants in the SARS-CoV-2 vaccination group reported more local and systemic local reactions than participants in the comparator group. In the further course, however, there were no higher odds of medical consultations in either of the two groups. Thus, altogether, we assume comparable safety.

TRIAL REGISTRATION

DRKS-ID DRKS00025881 and DRKS-ID DRKS00025373.

Coping Strategies for Pertussis Resurgence

Pertussis (whooping cough) is a respiratory disease caused primarily by Bordetella pertussis, a Gram-negative bacteria. Pertussis is a relatively contagious infectious disease in people of all ages, mainly affecting newborns and infants under 2 months of age. Pertussis is undergoing a resurgence despite decades of high rates of vaccination. To better cope with the challenge of pertussis resurgence, we evaluated its possible causes and potential countermeasures in the narrative review. Expanded vaccination coverage, optimized vaccination strategies, and the development of a new pertussis vaccine may contribute to the control of pertussis.

Improving vaccination rates in older adults and at-risk groups: focus on pertussis

Despite the implementation of effective paediatric vaccination programmes, pertussis remains a global health problem. Disease epidemiology has changed over time, shifting towards the adolescent and adult populations. In adults, the true burden of pertussis is greatly underestimated and pertussis vaccine coverage rates are suboptimal, including individuals with chronic conditions. Here, we report the outcomes of a virtual international scientific workshop to assess the evidence on the burden of pertussis in older adults and identify potential solutions to improve uptake of pertussis vaccines. In adults, pertussis is underdiagnosed in part due to atypical or milder clinical presentation and the lack of testing and case confirmation. However, contemporary epidemiological data denoted an increase in the burden of pertussis among adolescents and adults. This might be related to a variety of reasons including the waning of immunity over time, the lack of booster vaccination, and the improved diagnostic methods that led to increased recognition of the disease in adults. Pertussis sequelae can be severe in older adults, particularly those with existing chronic medical conditions, and the vulnerability of these groups is further enhanced by low pertussis vaccine coverage. Possible measures to increase vaccine uptake include strengthening and harmonisation of immunisation guidelines, healthcare professionals taking a more active role in recommending pertussis vaccination, involvement of vaccination centres and pharmacies in the vaccination process, and improving knowledge of pertussis burden and vaccine efficacy among the general population.

Immunogenicity and Safety of a Tetravalent Dengue Vaccine Administered Concomitantly or Sequentially With Tdap Vaccine: Randomized Phase IIIb Trial in Healthy Participants 9-60 Years of Age in the Philippines

BACKGROUND

Incorporating dengue vaccination into existing childhood vaccination programs could increase vaccine coverage. This study assessed the safety and immunogenicity of concomitant versus sequential administration of the combined tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccine and the tetravalent dengue vaccine (CYD-TDV).

METHODS

This phase IIIb, randomized, open-label, multicenter study was conducted in the Philippines in individuals 9-≤60 years of age (NCT02992418). Participants were to receive 3 CYD-TDV doses 6 months apart, the first dose administered either concomitantly or sequentially (28 days post-Tdap). Antibody levels were measured at baseline and 28 days post-first doses of Tdap vaccine and CYD-TDV, using enzyme-linked immunosorbent assay (pertussis, tetanus), micrometabolic inhibition test-toxin neutralization assay (diphtheria) and plaque reduction neutralization test (dengue). Immunogenicity was assessed for all participants, and statistical analysis reported for baseline dengue seropositive participants. Safety was assessed throughout.

RESULTS

Among 688 randomized participants, 629 (91.4%) were baseline dengue seropositive (concomitant group, n = 314 and sequential group, n = 315). After the first dose, non-inferiority of immune responses between concomitant and sequential vaccination was achieved; between-group geometric mean antibody concentration ratios were close to 1 for anti-PT, anti-FHA, anti-PRN and anti-FIM, between-group differences in percent achieving seroprotection (titers ≥0.1 IU/mL) were 0.26% (diphtheria) and 0.66% (tetanus), and between-group geometric mean antibody titer ratios were close to 1 for dengue serotypes 1-4. Safety profiles in both study groups were comparable.

CONCLUSIONS

CYD-TDV and Tdap vaccine administered concomitantly or sequentially in baseline dengue seropositive participants elicited comparable immunogenicity and safety profiles.

Safety of vaccines used for routine immunization in the United States: An updated systematic review and meta-analysis

BACKGROUND

Understanding the safety of vaccines is critical to inform decisions about vaccination. Our objective was to conduct a systematic review of the safety of vaccines recommended for children, adults, and pregnant women in the United States.

METHODS

We searched the literature in November 2020 to update a 2014 Agency for Healthcare Research and Quality review by integrating newly available data. Studies of vaccines that used a comparator and reported the presence or absence of key adverse events were eligible. Adhering to Evidence-based Practice Center methodology, we assessed the strength of evidence (SoE) for all evidence statements. The systematic review is registered in PROSPERO (CRD42020180089).

RESULTS

Of 56,603 reviewed citations, 338 studies reported in 518 publications met inclusion criteria. For children, SoE was high for no increased risk of autism following measles, mumps, and rubella (MMR) vaccine. SoE was high for increased risk of febrile seizures with MMR. There was no evidence of increased risk of  intussusception with rotavirus vaccine at the latest follow-up (moderate SoE), nor of diabetes (high SoE). There was no evidence of increased risk or insufficient evidence for key adverse events for newer vaccines such as 9-valent human papillomavirus and meningococcal B vaccines. For adults, there was no evidence of increased risk (varied SoE) or insufficient evidence for key adverse events for the new adjuvanted inactivated influenza vaccine and recombinant adjuvanted zoster vaccine. We found no evidence of increased risk (varied SoE) for key adverse events among pregnant women following tetanus, diphtheria, and acellular pertussis vaccine, including stillbirth (moderate SoE).

CONCLUSIONS

Across a large body of research we found few associations of vaccines and serious key adverse events; however, rare events are challenging to study. Any adverse events should be weighed against the protective benefits that vaccines provide.

ERRATA CORRIGE

[This corrects the article on p. E530-E541 in vol. 61, PMID: 33628957.].

An observational study of antibody responses to a primary or subsequent pertussis booster vaccination in Australian healthcare workers

Adult pertussis vaccination is increasingly recommended to control pertussis in the community. However, there is little data on the duration and kinetics of immunity to pertussis boosters in adults. We compared IgG responses to vaccination with a tetanus, low-dose diphtheria, low-dose acellular pertussis (Tdap) booster at 1 week, 1 month and 1 year post-vaccination in whole-cell (wP)-primed Australian paediatric healthcare workers who had received an adult Tdap booster 5-12 years previously, to those who received their first Tdap booster. Tdap vaccination was well tolerated in both groups. Previously boosted adults had significantly higher pre-vaccination IgG concentrations for all vaccine-antigens, and more were seropositive for pertussis toxin (PT)-specific IgG (≥ 5 IU/mL) (69.5%; 95% confidence interval (CI) 59.5-79.5) than adults in the naïve group (45.2%; 95% CI 32.8-57.5). Tdap vaccination significantly increased IgG responses 1 month post-vaccination in both groups. This increase was more rapid in previously boosted than in naïve adults, with geometric mean fold-increases in PT-IgG at 1 week post vaccination of 3.6 (95% CI 2.9-4.3) and 2.6 (95% CI 2.2-3.2), respectively. Antibody waning between 1 month and 1 year post-vaccination was similar between groups for IgG specific to PT and filamentous haemagglutinin (FHA), but was faster for IgG against pertactin (PRN) in the naïve group (GMC ratio 0.36; 95% CI 0.31-0.42) than the previously boosted group (GMC ratio 0.45; 95% CI 0.39-0.50). At baseline, all but one adult had protective IgG titres against tetanus toxin (TT) (≥ 0.1 IU/mL), and 75.6% in the previously boosted and 61.3% in the naïve group had protective IgG titres against diphtheria toxoid (DT) of ≥ 0.1 IU/mL. This study shows that pertussis immune memory is maintained up to 12 years after Tdap vaccination in wP-primed Australian adults. There was no evidence that pertussis immune responses waned faster after a booster dose. These findings support current recommendations of repeating Tdap booster vaccination in paediatric healthcare workers at least every 10 years. Clinical trials registry: ACTRN12615001262594.

Immunogenicity and antibody persistence of diphteria-tetanus-acellular pertussis vaccination in adolescents and adults: a systematic review of the literature showed different responses to the available vaccines

INTRODUCTION

In industrialized countries, the routine use of Bordetella pertussis vaccines has shifted the burden of Bordetella pertussis disease from children to infants, adolescents and adults, leading to the necessity for booster doses.

MATERIALS AND METHODS

We prepared a review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) with the aims of: a) describing the immunogenicity of the main available vaccines for adolescents and adults; b) describing antibody persistence after immunization with the main vaccines available in childhood and adults and, also, possible co-administration; and c) identifying the gold standard for adolescent and adult immunizations.

RESULTS

We identified 6906 records. After removing duplicate records, we included 12 RCT (Randomized Controlled Trial) (people aged 11-73): 7 of these studies had only 1 control group, 4 had 2 control groups and 1 had 5 control groups; moreover, of the 12 studies included, only 2 regarded co-administration, while all concerned immunogenicity. Nine of the 12 studies had a Jadad score above 3 points, and 10 out of 12 met the criteria of Cochrane Back Review Group Criteria List for Methodological Quality Assessment.

DISCUSSION AND CONCLUSION

We found a limited number of good-quality RCTs investigating our object. The 5-component vaccines, although containing a lower dose of antigen, proved more effective than the 1-component vaccine. Evidence supports the use of 5-component vaccines for booster sessions in adolescence and adulthood.

Use of Tetanus Toxoid, Reduced Diphtheria Toxoid, and Acellular Pertussis Vaccines: Updated Recommendations of the Advisory Committee on Immunization Practices - United States, 2019

Since 2005, a single dose of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine has been recommended by the Advisory Committee on Immunization Practices (ACIP) for adolescents and adults (1,2). After receipt of Tdap, booster doses of tetanus and diphtheria toxoids (Td) vaccine are recommended every 10 years or when indicated for wound management. During the October 2019 meeting of ACIP, the organization updated its recommendations to allow use of either Td or Tdap where previously only Td was recommended. These situations include decennial Td booster doses, tetanus prophylaxis when indicated for wound management in persons who had previously received Tdap, and for multiple doses in the catch-up immunization schedule for persons aged ≥7 years with incomplete or unknown vaccination history. Allowing either Tdap or Td to be used in situations where Td only was previously recommended increases provider point-of-care flexibility. This report updates ACIP recommendations and guidance regarding the use of Tdap vaccines (3).

Diphtheria

Diphtheria is a potentially fatal infection mostly caused by toxigenic Corynebacterium diphtheriae strains and occasionally by toxigenic C. ulcerans and C. pseudotuberculosis strains. Diphtheria is generally an acute respiratory infection, characterized by the formation of a pseudomembrane in the throat, but cutaneous infections are possible. Systemic effects, such as myocarditis and neuropathy, which are associated with increased fatality risk, are due to diphtheria toxin, an exotoxin produced by the pathogen that inhibits protein synthesis and causes cell death. Clinical diagnosis is confirmed by the isolation and identification of the causative Corynebacterium spp., usually by bacterial culture followed by enzymatic and toxin detection tests. Diphtheria can be treated with the timely administration of diphtheria antitoxin and antimicrobial therapy. Although effective vaccines are available, this disease has the potential to re-emerge in countries where the recommended vaccination programmes are not sustained, and increasing proportions of adults are becoming susceptible to diphtheria. Thousands of diphtheria cases are still reported annually from several countries in Asia and Africa, along with many outbreaks. Changes in the epidemiology of diphtheria have been reported worldwide. The prevalence of toxigenic Corynebacterium spp. highlights the need for proper clinical and epidemiological investigations to quickly identify and treat affected individuals, along with public health measures to prevent and contain the spread of this disease.

Antibody persistence and safety and immunogenicity of a second booster dose nine years after a first booster vaccination with a reduced antigen diphtheria-tetanus-acellular pertussis vaccine (Tdap) in adults

BACKGROUND

Over the last decades, pertussis showed periodic increases in its incidence among adults, despite being a vaccine-preventable disease.

METHODS

This phase III, multicenter, extension study (NCT00489970) was conducted in adults from the United States, followed at Year (Y) 5 and Y9 post-vaccination with a dose of reduced-antigen-content tetanus-diphtheria-acellular pertussis vaccine containing either 3 (Tdap-B group) or 5 pertussis components (Tdap-A group). Willing participants in Tdap groups and newly-recruited participants (Control group) received one Tdap-B dose at Y9. Antibody persistence (at Y5 and Y9) and safety of Tdap-B at Y9 were assessed. Non-inferiority of immune response elicited by 2 Tdap doses was evaluated at Y9: (i) versus one Tdap-B dose for diphtheria and tetanus in terms of seroprotection rates; (ii) for all antigens in terms of booster response rates (Tdap-B and Tdap-A groups versus Control group); and (iii) for pertussis antigens in terms of geometric mean concentrations (GMCs) versus a 3-dose series of a combined diphtheria-tetanus-acellular pertussis vaccine (DTPa) administered during infancy.

RESULTS

1257 participants were enrolled at Y5 and 809 participants were vaccinated at Y9. Seroprotection rates in both Tdap groups were ≥98.4% and ≥98.0% (Y5) and ≥98.3% and ≥98.1% (Y9) for diphtheria and tetanus, respectively. For pertussis antigens, antibody concentrations above assay cut-offs were observed for ≥76.6% (Y5) and ≥84.9% (Y9) of participants in Tdap groups. At Y9, one month post-Tdap vaccination, comparable seroprotection/seropositivity rates and antibody GMCs were observed among groups. Non-inferiority of immune responses in both Tdap groups was demonstrated when compared to the Control group for diphtheria and tetanus and to a 3-dose DTPa series for pertussis antigens. Non-inferiority criteria in terms of booster response were not met for all antigens. No safety concerns were raised.

CONCLUSION

A second dose of Tdap-B administered in adults, 9 years after initial Tdap vaccination, is immunogenic and well-tolerated.

Humoral immunity 10 years after booster immunization with an adolescent and adult formulation combined tetanus, diphtheria, and 5-component acellular pertussis vaccine in the USA

BACKGROUND

In a prospective, randomized pivotal phase III clinical trial, the immunogenicity and reactogenicity of a tetanus-diphtheria-acellular pertussis vaccine (Tdap) and a tetanus-diphtheria vaccine (Td) vaccine were studied in participants aged 11-64 years. Here we report antibody persistence through 10 years after vaccination.

METHODS

Participants who received Tdap or Td in the original phase III trial and provided pre- and post-vaccination serum samples were recruited to donate sera at 1, 3, 5 and 10 years post-vaccination. Antibody concentrations were measured using standard assay techniques.

RESULTS

Initially, 1457 Tdap and 1152 Td recipients were included; of these, 175 persons from Tdap group were available at the final study bleed point. Nearly all adolescents in both groups had diphtheria antibody levels ≥0.1 IU/mL 1 month after vaccination, which were maintained in ≥95% of vaccinees at 5 and 10 years. Among adults, ≥94% had diphtheria antibody levels ≥0.1 IU/mL 1 month after vaccination, which were maintained in ≥80% at 5 and 10 years. Nearly all participants had tetanus antibodies ≥0.1 IU/mL throughout the study. PT antibodies declined to pre-vaccination levels approximately 5 years post-vaccination; FHA, PRN and FIM antibodies waned at 5 and 10 years but remained several-fold higher than pre-vaccination levels.

CONCLUSIONS

Tdap and Td provide long-lasting protective immune responses against diphtheria and tetanus. Pertussis antibodies following Tdap generally exceeded pre-vaccination levels throughout the study, but showed substantial waning. These data may inform discussion of the need for repeat Tdap booster vaccinations among adults.

TRIAL REGISTRATION

The original phase III clinical trial, as well as the 1-, 3-, and 5-year serology follow-up studies were conducted prior to mandatory registration. The 10-year serology follow-up data collection was performed as part of a repeat Tdap administration clinical trial that was registered under clinicaltrials.gov number NCT01439165.