Assessment of Tdap Vaccination Effectiveness in Adolescents in Integrated Health-Care Systems

Assessing the Impact of the 2020 Council of State and Territorial Epidemiologists Case Definition for Pertussis on Reported Pertussis Cases

BACKGROUND

In 2020, the Council of State and Territorial Epidemiologists (CSTE) pertussis case definition was modified; the main change was classifying polymerase chain reaction (PCR)-positive cases as confirmed, regardless of cough duration. Pertussis data reported through Enhanced Pertussis Surveillance (EPS) in 7 sites and the National Notifiable Diseases Surveillance System (NNDSS) were used to evaluate the impact of the new case definition.

METHODS

We compared the number of EPS cases with cough onset in 2020 to the number that would have been reported based on the prior (2014) CSTE case definition. To assess the impact of the change nationally, the proportion of EPS cases newly reportable under the 2020 CSTE case definition was applied to 2020 NNDSS data to estimate how many additional cases were captured nationally.

RESULTS

Among 442 confirmed and probable cases reported to EPS states in 2020, 42 (9.5%) were newly reportable according to the 2020 case definition. Applying this proportion to the 6124 confirmed and probable cases reported nationally in 2020, we estimated that the new definition added 582 cases. Had the case definition not changed, reported cases in 2020 would have decreased by 70% from 2019; the observed decrease was 67%.

CONCLUSIONS

Despite a substantial decrease in reported pertussis cases in the setting of coronavirus disease 2019 (COVID-19), our data show that the 2020 pertussis case definition change resulted in additional case reporting compared with the previous case definition, providing greater opportunities for public health interventions such as prophylaxis of close contacts.

The durability of vaccine-induced protection: an overview

INTRODUCTION

Current vaccines vary widely in both their efficacy against infection and disease, and the durability of the efficacy. Some vaccines provide practically lifelong protection with a single dose, while others provide only limited protection following annual boosters. What variables make vaccine-induced immune responses last? Can breakthroughs in these factors and technologies help us produce vaccines with better protection and fewer doses? The durability of vaccine-induced protection is now a hot area in vaccinology research, especially after COVID-19 vaccines lost their luster. It has fueled discussion on the eventual utility of existing vaccines to society and bolstered the anti-vaxxer camp. To sustain public trust in vaccines, lasting vaccines must be developed.

AREAS COVERED

This review summarizes licensed vaccines' protection. It analyses immunological principles and vaccine and vaccinee parameters that determine longevity of antibodies. The review concludes with challenges and the way forward to improve vaccine durability.

EXPERT OPINION

Despite enormous advances, we still lack essential markers and reliable correlates of lasting protection. Most research has focused on humoral immune responses, but we must also focus on innate, mucosal, and cellular responses - their assessment, correlates, determinants, and novel adjuvants. Suitable vaccine designs and platforms for durable immunity must be found.

Vaccination schedule for adolescents. Consensus of the AEV, CAV-AEP and SEMA

We present the consensus document on the immunization schedule for adolescents developed by 3 scientific societies: the Spanish Association of Pediatrics (AEP), through its Advisory Committee on Vaccines (CAV-AEP), the Spanish Society of Adolescent Medicine (SEMA) and the Spanish Association of Vaccinology (AEV). There are particularities in infectious disease during adolescence, such as an increased susceptibility to pertussis, poorer outcomes of chickenpox, mumps and hepatitis A, a high incidence of sexually transmitted infections or increased prevalence of meningococcal carriage. The document analyses the schedule for adolescents in the context of vaccination policy overall. It contemplates the vaccines to be included in the immunization schedule for healthy adolescents: against invasive meningococcal disease (tetravalent ACWY and B), against human papillomavirus (which should be gender-neutral), against pertussis, against influenza and against SARS-CoV-2 (in unvaccinated individuals and at-risk groups). It is worth noting that the 4CMenB vaccine appears to confer some protection against gonococcal infection, which would be a considerable added value for adolescents. The vaccination of adolescents belonging to risk groups or travelling abroad also needs to be contemplated, as is the case in any other age group. Vaccination against hepatitis A, which is included in the routine immunization schedule of Catalonia, Ceuta and Melilla from the second year of life, should also be considered a priority in adolescents traveling to endemic areas.

Chapter Controlled Human Infection with Bordetella pertussis

Bordetella pertussis, a slow-growing Gram-negative coccobacillus and the causative agent of whooping cough, is one of the leading causes of vaccine-preventable death and morbidity globally. A state of asymptomatic human carriage has not yet been demonstrated by population studies but is likely to be an important reservoir for community transmission of infection. Such a carriage state may be a target for future vaccine strategies. This chapter presents a short summary of the characteristics of B. pertussis, which should be taken into account when developing a human challenge model and any future experimental medicine interventions. Three studies involving deliberate infection with B. pertussis have been described to date. The first of these was a scientifically and ethically unacceptable paediatric challenge study involving four children in 1930. The second was an investigation of a putative live vaccine using a genetically modified and attenuated strain of B. pertussis. Finally, a systematically constructed human challenge model using a wild-type, potentially pathogenic strain has been established. The latter study has demonstrated that deliberate induction of asymptomatic colonisation in humans is safe and immunogenic, with colonised participants exhibiting seroconversion to pertussis antigens. It has also shown nasal wash to be a more sensitive method of detecting the presence of B. pertussis than either pernasal swab or throat swab, and that B. pertussis carriage can be cleared effectively with Azithromycin. The development of this wild-type B. pertussis human challenge model will allow the investigation of host-pathogen and facilitate future vaccine development.

Pertussis vaccine effectiveness and duration of protection - A systematic review and meta-analysis

A comprehensive review of observational pertussis vaccine effectiveness (VE) studies is needed to update gaps from previous reviews. We conducted a systematic review of VE and duration of protection studies for the whole-cell (wP) and acellular (aP) pertussis vaccines and conducted a formal meta-analysis using random effects models. Evidence continues to suggest that receipt of any pertussis vaccine confers protection in the short-term against disease although this protection wanes rapidly for aP vaccine. We detected significant heterogeneity in pooled estimates due, in part, to factors such as bias and confounding which may be mitigated by study design. Our review of possible sources of heterogeneity may help interpretation of other VE studies and aid design decisions in future pertussis VE research.

Boosting Teenagers With Acellular Pertussis Vaccines Containing Recombinant or Chemically Inactivated Pertussis Toxin: A Randomized Clinical Trial

BACKGROUND

Protection induced by acellular pertussis (aP) vaccines is partial and short-lived, especially in teenagers, calling for novel immunization strategies.

METHODS

We conducted an investigator-driven proof-of-concept randomized controlled trial in aP-primed adolescents in Geneva to assess the immunogenicity and reactogenicity of a novel recombinant aP (r-aP) vaccine including recombinant pertussis toxin (PT) and filamentous hemagglutinin (FHA) coadministered with tetanus-diphtheria toxoids (Td), compared to a licensed tetanus-diphtheria-aP vaccine containing chemically detoxified PT (cd/Tdap). The primary immunological endpoints were day 28/365 geometric mean concentrations (GMCs) of total and neutralizing anti-PT antibodies. Memory B cells were assessed.

RESULTS

Sixty-two aP-primed adolescents were randomized and vaccinated with r-aP + Td or cd/Tdap. Reactogenicity, adverse events, and baseline GMCs were similar between the groups. Day 28 PT-neutralizing GMCs were low after cd/Tdap (73.91 [95% confidence interval {CI}, 49.88-109.52] IU/mL) and approximately 2-fold higher after r-aP + Td (127.68 [95% CI, 96.73-168.53] IU/mL; P = .0162). Anti-PT GMCs were also low after cd/Tdap (52.43 [95% CI, 36.41-75.50] IU/mL) and 2-fold higher after r-aP + Td (113.74 [95% CI, 88.31-146.50] IU/mL; P = .0006). Day 28 anti-FHA GMCs were similar in both groups. Day 365 anti-PT (but not PT-neutralizing) GMCs remained higher in r-aP + Td vaccinees. PT-specific memory B cells increased significantly after r-aP + Td but not cd/Tdap boosting.

CONCLUSIONS

Boosting aP-primed adolescents with r-aP induced higher anti-PT and PT-neutralizing responses than cd/Tdap and increased PT-specific memory B cells. Despite this superior immunogenicity, r-aP may have to be given repeatedly, earlier, and/or with novel adjuvants to exert an optimal influence in aP-primed subjects.

CLINICAL TRIALS REGISTRATION

NCT02946190.

Tetanus, diphtheria and acellular pertussis (Tdap) vaccine for prevention of pertussis among adults aged 19 years and older in the United States: A cost-effectiveness analysis

Currently, the Advisory Committee on Immunization Practices recommends one-time tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccination for all adults 19 years and older. This study is designed to evaluate the cost-effectiveness of Tdap vaccination for Tdap-eligible adults aged 19 through 85 in the United States. A cost-effectiveness model was developed to compute costs and health outcomes associated with pertussis among 100,000 Tdap-eligible persons of each age cohort. From the societal perspective, the cost per quality-adjusted life-year (QALY) saved was evaluated under the vaccination scenarios. Sensitivity analyses were also conducted to evaluate the impacts of changes in key variables. All costs were adjusted to 2018 US$ with an annual discount rate of 3% applied to costs and outcomes. The incremental cost-effectiveness ratios (ICERs) for vaccinating US adults aged 19 to 85 with Tdap ranged from $248,000/QALY to $900,000/QALY. The lowest cost per QALY was found to be $248,000 for the age 65 cohort, followed by $332,000 for the cohort of age 19, and followed by $477,000 for the age 50 cohort. Sensitivity analysis showed the most dramatic changes in ICER occurred when changing the underreporting factor, vaccine effectiveness and vaccination costs. While Tdap vaccination may not be as cost effective as predicted earlier, it remains the best available preventive measure against pertussis. Further investigation of the true burden of pertussis disease among adults and the effectiveness of Tdap vaccination in this population is needed to better estimate the impact of Tdap vaccination.

Adolescent vaccinations: updates for the general practitioner

PURPOSE OF REVIEW

Adolescent providers have a unique opportunity to interface with adolescents during a transformative time period. Optimizing vaccinations may protect teens against preventable but potentially deadly diseases. Healthcare providers must be aware of the evolving vaccination data and up-to-date recommendations for vaccinations.

RECENT FINDINGS

In spite of the Center for Disease Control recommendations, there is a gap between the actual and desired vaccination rates of adolescents. Tetanus, diphtheria, and acellular pertussis, meningococcal against ACWY serotypes, and human papillomavirus (HPV) are vaccinations unique to the adolescent period. There has been a marked increase in pertussis cases over the last 2 decades. Either of the meningitis B vaccines may be given to 16-18 year olds and are effective in controlling college outbreaks. Increasing evidence continues to demonstrate the safety and efficacy of the HPV vaccination, although a substantial number of adolescents remain unvaccinated. Fortunately, there are proven strategies to remedy this.

SUMMARY

Adolescent providers should be aware of the increase in pertussis cases over the past 2 decades and the Category B recommendation for meningococcal B vaccine at 16-18 years, and they should work towards closing the gap between the actual and desired HPV vaccination rates.