Epidemiological and Economic Effects of Priming With the Whole-Cell Bordetella pertussis Vaccine

A Sensitive Public Health Issue—The Vaccine Acceptancy and the Anti-Pertussis Immune Status of Pregnant Women from a Romanian Metropolitan Area

(1) Background: Immunization of pregnant women (PWs) against Bordetella pertussis infection is still a challenging health matter. (2) Methods: We gathered questionnaire data from 180 PWs regarding their expectancies and current opinion on infectious disease prevention. For the group of PWs who agreed to further investigations, the serum levels of Ig G anti-B. pertussis antibodies (IgG-PT) titer were measured and analyzed. (3) Results: A total of 180 PWs completed the questionnaire and 98 (54.44%, study group) accepted to perform the laboratory tests. During the first two pregnancy trimesters, PWs were found to be more willing (compared with the control group) to test for identifying high-risk situations that could affect themselves and their future infant (p < 0.001). Most of the participating PWs (91, 91.9%) had low levels of anti-pertussis antibodies (values < 40 IU/mL). Declared vaccine coverage of the PWs newborn infants for DTaP-1 and Prevenar 13 (at 2 months) and DTaP-2 and Prevenar 13 (at 4 months) vaccination reached 100% in the study group, while in the control group only 30/82 (36.59%) PWs accepted to be vaccinated during pregnancy, none of them providing data on their infants’ vaccine coverage. (4) Conclusions: Enrolled PWs faced a waning immunity against the B. pertussis infection. By raising maternal confidence in the protective role of vaccines against infectious diseases, better vaccine acceptance and better infant vaccine coverage can be achieved.

Evaluation of Whole-Cell and Acellular Pertussis Vaccines in the Context of Long-Term Herd Immunity

After the pertussis vaccine had been introduced in the 1940s and was shown to be very successful in reducing the morbidity and mortality associated with the disease, the possibility of improving both vaccine composition and vaccination schedules has become the subject of continuous interest. As a result, we are witnessing a considerable heterogeneity in pertussis vaccination policies, which remains beyond universal consensus. Many pertussis-related deaths still occur in low- and middle-income countries; however, these deaths are attributable to gaps in vaccination coverage and limited access to healthcare in these countries, rather than to the poor efficacy of the first generation of pertussis vaccine consisting in inactivated and detoxified whole cell pathogen (wP). In many, particularly high-income countries, a switch was made in the 1990s to the use of acellular pertussis (aP) vaccine, to reduce the rate of post-vaccination adverse events and thereby achieve a higher percentage of children vaccinated. However the epidemiological data collected over the past few decades, even in those high-income countries, show an increase in pertussis prevalence and morbidity rates, triggering a wide-ranging debate on the causes of pertussis resurgence and the effectiveness of current pertussis prevention strategies, as well as on the efficacy of available pertussis vaccines and immunization schedules. The current article presents a systematic review of scientific reports on the evaluation of the use of whole-cell and acellular pertussis vaccines, in the context of long-term immunity and vaccines efficacy.

Vaccine-Induced Cellular Immunity against Bordetella pertussis: Harnessing Lessons from Animal and Human Studies to Improve Design and Testing of Novel Pertussis Vaccines

Pertussis ('whooping cough') is a severe respiratory tract infection that primarily affects young children and unimmunised infants. Despite widespread vaccine coverage, it remains one of the least well-controlled vaccine-preventable diseases, with a recent resurgence even in highly vaccinated populations. Although the exact underlying reasons are still not clear, emerging evidence suggests that a key factor is the replacement of the whole-cell (wP) by the acellular pertussis (aP) vaccine, which is less reactogenic but may induce suboptimal and waning immunity. Differences between vaccines are hypothesised to be cell-mediated, with polarisation of Th1/Th2/Th17 responses determined by the composition of the pertussis vaccine given in infancy. Moreover, aP vaccines elicit strong antibody responses but fail to protect against nasal colonisation and/or transmission, in animal models, thereby potentially leading to inadequate herd immunity. Our review summarises current knowledge on vaccine-induced cellular immune responses, based on mucosal and systemic data collected within experimental animal and human vaccine studies. In addition, we describe key factors that may influence cell-mediated immunity and how antigen-specific responses are measured quantitatively and qualitatively, at both cellular and molecular levels. Finally, we discuss how we can harness this emerging knowledge and novel tools to inform the design and testing of the next generation of improved infant pertussis vaccines.

Cost-Effectiveness of Pertussis Vaccination Schedule in Israel

Pertussis is a highly contagious bacterial disease that primarily affects infants. To optimize the pertussis vaccination schedule in Israel and evaluate the cost-effectiveness of alternative strategies that add or remove booster doses, we developed an age-structured model for pertussis transmission. Our model was calibrated using 16 years of data from laboratory-confirmed pertussis cases in Israel. Costs and quality-adjusted life years (QALYs) projected by the model within 12 years from the implementation of the considered interventions were compared with the current vaccination schedule. We found that by using the same number of vaccines administered today, the targeting of children at the age of six instead of seven would be predicted to be the optimal schedule to decrease both outpatient visits and hospitalizations. We also found that any increase in maternal vaccination coverage is likely to be cost-effective, with an incremental cost-effectiveness ratio of $77,000–$97,000 per QALY. By contrast, the contribution of the second booster dose is limited, with a probability of only 0.6 to be cost-effective at $110,000/QALY saved. Additional effort should be invested to encourage maternal vaccination against pertussis. We recommend moving the first booster to age six and prudently considering the necessity of the second booster dose.

Cost-effectiveness of maternal pertussis immunization: Implications of a dynamic transmission model for low- and middle-income countries

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(84) Low- and middle-income countries (LMICs) have experienced a resurgence of pertussis.

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(74) Maternal aP immunization could prevent pertussis among very young infants.

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(84) A dynamic transmission model was used to evaluate maternal aP immunization in LMICs.

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(82) Maternal aP is cost-effective when infant vaccination coverage is moderate or low.

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(85) Maternal aP immunization is not cost-effective in LMICs with infant coverage 90-95%.

Objective

This study evaluates the cost-effectiveness of maternal acellular pertussis (aP) immunization in low- and middle-income countries using a dynamic transmission model.

Methods

We developed a dynamic transmission model to simulate the impact of infant vaccination with whole-cell pertussis (wP) vaccine with and without maternal aP immunization. The model was calibrated to Brazilian surveillance data and then used to project health outcomes and costs under alternative strategies in Brazil, and, after adjusting model parameter values to reflect their conditions, in Nigeria and Bangladesh. The primary measure of cost-effectiveness is incremental cost (2014 USD) per disability-adjusted life-year (DALY).

Results

The dynamic model shows that maternal aP immunization would be cost-effective in Brazil, a middle-income country, under the base-case assumptions, but would be very expensive at infant vaccination coverage in and above the threshold range necessary to eliminate the disease (90–95%). At 2007 infant coverage (DTP1 90%, DTP3 61% at 1 year of age), maternal immunization would cost < $4,000 per DALY averted. At high infant coverage, such as Brazil in 1996 (DTP1 94%, DTP3 74% at 1 year), cost/DALY increases to $1.27 million. When the model’s time horizon was extended from 2030 to 2100, cost/DALY increased under both infant coverage levels, but more steeply with high coverage. The results were moderately sensitive to discount rate, maternal vaccine price, and maternal aP coverage and were robust using the 100 best-fitting parameter sets. Scenarios representing low-income countries showed that maternal aP immunization could be cost-saving in countries with low infant coverage, such as Nigeria, but very expensive in countries, such as Bangladesh, with high infant coverage.

Conclusion

A dynamic model, which captures the herd immunity benefits of pertussis vaccination, shows that, in low- and middle-income countries, maternal aP immunization is cost-effective when infant vaccination coverage is moderate, even cost-saving when it is low, but not cost-effective when coverage levels pass 90–95%.

Comparison of adverse events following immunisation with acellular and whole-cell pertussis vaccines: A systematic review

INTRODUCTION

Two types of vaccines are currently licensed for use against pertussis: whole-cell (wP) and acellular pertussis (aP). There is evidence that wP confers more durable immunity than aP, however wP has been more frequently associated with adverse events following immunisation (AEFI). A comparison of the frequency of AEFI with the first doses of wP and aP has not yet been clearly documented. This must be done in light of recent considerations to move towards a wP prime-aP boost vaccination strategy in low and middle-income countries.

OBJECTIVES

To compare the frequency of AEFI associated with the first dose of the wP and aP vaccines. We also compared the frequency of AEFI associated with subsequent doses of wP.

METHODS

This systematic review was carried out in strict accordance with the published protocol.

RESULTS

High heterogeneity amongst included one-armed studies did not allow for pooling of prevalence estimates. The prevalence estimates of AEFI at first vaccine dose of wP ranged from 0 to 75%, while the prevalence estimates of AEFI at first vaccine dose of aP ranges from 0 to 39%. The prevalence estimates of adverse events following second and third vaccine dose of wP ranged from 0 to 71% and 0 to 61%, respectively. Risk ratios among two-armed studies showed an increased risk of adverse events with first dose of wP compared to aP [local reaction RR 2.73 (2.33, 3.21), injection site pain RR 4.15 (3.24, 5.31), injection site swelling RR 4.38 (2.70, 7.12), fever over 38 °C RR 9.21 (5.39, 15.76), drowsiness RR 1.34 (1.18, 1.52) and vomiting RR 1.28 (0.91, 1.79)].

CONCLUSION

Our results confirm that, when comparing the first dose, wP is more reacotgenic than aP. The proposed wP prime followed by aP boost pertussis vaccine strategy should be approached with caution.

Th1/Th17 polarization persists following whole-cell pertussis vaccination despite repeated acellular boosters

In the mid-1990s, whole-cell pertussis (wP) vaccines were associated with local and systemic adverse events that prompted their replacement with acellular pertussis (aP) vaccines in many high-income countries. In the past decade, rates of pertussis disease have increased in children receiving only aP vaccines. We compared the immune responses to aP boosters in individuals who received their initial doses with either wP or aP vaccines using activation-induced marker (AIM) assays. Specifically, we examined pertussis-specific memory CD4+ T cell responses ex vivo, highlighting a type 2/Th2 versus type 1/Th1 and Th17 differential polarization as a function of childhood vaccination. Remarkably, after a contemporary aP booster, cells from donors originally primed with aP were (a) associated with increased IL-4, IL-5, IL-13, IL-9, and TGF-β and decreased IFN-γ and IL-17 production, (b) defective in their ex vivo capacity to expand memory cells, and (c) less capable of proliferating in vitro. These differences appeared to be T cell specific, since equivalent increases of antibody titers and plasmablasts after aP boost were seen in both groups. In conclusion, our data suggest that there are long-lasting effects and differences in polarization and proliferation of T cell responses in adults originally vaccinated with aP compared with those that initially received wP, despite repeated acellular boosters.

Whole-Cell or Acellular Pertussis Primary Immunizations in Infancy Determines Adolescent Cellular Immune Profiles

Introduction

Pertussis is re-emerging worldwide, despite effective immunization programs for infants and children. Epidemiological studies show a more limited duration of protection against clinical pertussis in adolescents primed with acellular pertussis (aP) vaccines during infancy than those who have been primed with whole-cell pertussis (wP) vaccines. This study aimed to determine whether memory immune responses to aP, diphtheria, and tetanus vaccine antigens following booster vaccinations at 4 and 9 years of age differ between wP- versus aP-primed children.

Methods

In a cross-sectional study, blood was collected of DTwP- or diphtheria, tetanus, and aP (DTaP)-primed children before, 1 month, and 2 years after the preschool DTaP booster administered at 4 years of age (n = 41–63 per time point). In a longitudinal study, blood was sampled of DTwP- or DTaP-primed children before, 1 month, and 1 year after a preadolescent Tdap booster at 9 years of age (n = 79–83 per time point). Pertussis, diphtheria, and tetanus vaccine antigen-specific IgG levels, B-cell and T-cell responses were determined.

Results

After the preschool booster vaccination, IgG levels were significantly higher in aP-primed as compared with wP-primed children until 6 years of age. Before the preadolescent Tdap booster vaccination, humoral and cellular immune responses were similar in aP- and wP-primed children. However, the Tdap booster vaccination induced lower vaccine antigen-specific humoral, B-cell, and T-helper 1 (Th1) cell responses resulting in significantly lower Th1/Th2 ratios in aP-primed compared with wP-primed children.

Conclusion

The memory immune profiles at preadolescent age to all DTaP vaccine antigens are already determined by the wP or aP combination vaccines given in infancy, showing a beneficial Th1-dominated response after wP-priming. These immunological data corroborate epidemiological data showing that DTaP-primed adolescents are less protected against clinical pertussis than DTwP-primed children.

Use of acellular pertussis vaccines in the United States: can we do better?

INTRODUCTION

Despite robust vaccination schedules and high vaccination rates, many countries, including the U.S., have seen large pertussis outbreaks with a shift in recent years in the distribution of disease burden towards adolescents and young adults. Areas covered: This perspective covers problems related to the increased incidence of pertussis among adolescents. Because the Tdap vaccine only protects against pertussis for 1-2 years after vaccination, we propose a new strategy which aims to optimize the benefit of Tdap in adolescents. Expert commentary: Current pertussis vaccination schedules are based on age and have not been effective at protecting adolescents and teenagers from pertussis outbreaks. An alternative to the current practice would be to take advantage of the cyclical nature of pertussis outbreaks. Rather than immunizing children and adolescent solely based on age regardless of risk of pertussis at that moment, perhaps we should consider a 'timed' Tdap. The goal would be to administer Tdap to susceptible adolescents and young adults during periods when there is a greater risk of being exposed to pertussis. This approach would optimize the use of an effective, but short-lived vaccine by maximizing protection at the time of increased risk.

Adverse events following primary and secondary immunisation with whole-cell pertussis: a systematic review protocol

INTRODUCTION

Pertussis is a contagious respiratory illness caused by the bacterium Bordetella pertussis. Two types of vaccines are currently available against the disease: whole-cell pertussis (wP) and acellular pertussis (aP). With the shift of high-income countries from wP to aP as a result of adverse events following immunisation (AEFI), an upsurge in reported cases of pertussis has been noticed. Owing to this, it is proposed to use wP as a prime and aP for boost vaccination strategy. However, a comparison of the AEFI with the first doses of wP and aP are not clearly documented.

METHODS AND ANALYSIS

The primary outcomes of interest are AEFI with dose 1 of wP, subsequent doses of wP and dose 1 of aP. As a secondary outcome frequency of AEFI with wP will be compared with the AEFI of doses 2 and 3 of wP and dose 1 of aP. Electronic databases will be searched and two authors will screen the titles and abstracts of the output. Full texts will then be independently reviewed by the first author and two other authors. Qualifying studies will then be formally assessed for quality and risk of bias using a scoring tool. Following standardised data extraction, statistical analysis will be carried out using STATA. Where data are available, subgroup analyses will be performed. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines will be followed in reporting the findings of the systematic review and meta-analysis.

ETHICS AND DISSEMINATION

No ethics approval is required as the systematic review will use only published data already in the public domain. Findings will be disseminated through publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

This protocol has been registered with the International Prospective Register of Systematic Reviews (PROSPERO), registration number CRD42016035809.

Vaccination and unexplained sudden death risk in Taiwanese infants

PURPOSE

In March 1992, eight infants who had died within 36 hours of receiving whole-cell pertussis vaccine (diphtheria, tetanus, and whole-cell pertussis [DTwP]) prompted the Taiwan health authorities to suspend its use. We conducted an investigation of vaccination and sudden unexplained infant death (SUID) and repeated it more recently after Taiwan switched to acellular pertussis vaccine (diphtheria, tetanus, and acellular pertussis [DTaP]) in 2010.

METHODS

All SUIDs aged 31-364 days during 1990-1992 and 1996-2013 were selected from the death registration databases. The case-control investigation matched each case to two controls on clinic, sex, and birth date, whereas the follow-up self-controlled case series study compared risk of death during the 30-day post-vaccination risk periods with those in the control periods within the same case.

RESULTS

Sudden unexplained infant death was associated with never receiving DTwP (odds ratio 2.28, 95% confidence interval 1.25-4.15) in the case-control investigation. The odds ratios within 0-1, 2-7, 8-14, and 15-30 days of DTwP administration were 1.18, 0.26, 0.50, and 0.77. In the 1996-2013 self-controlled case series studies, this temporal shift between DTwP and SUID was consistently observed for female (incidence rate ratio 1.70, 0.75, 1.01, and 0.84) but not male or DTaP recipients. A pooled analysis showed significant risk within 2 days of receiving DTwP in female infants (incidence rate ratio 1.66, 95% confidence interval 1.05-2.60).

CONCLUSIONS

Being unvaccinated and recent receipt of DTwP in female infants was significantly associated with SUID; the latter was consistent with a temporal shift pattern without overall increase in risk. The currently used pertussis vaccine, DTaP, did not increase risk of SUID. Copyright © 2016 John Wiley & Sons, Ltd.

Effectiveness of pertussis vaccination and duration of immunity

BACKGROUND

A resurgence of pertussis cases among both vaccinated and unvaccinated people raises questions about vaccine effectiveness over time. Our objective was to study the effectiveness of the pertussis vaccine and characterize the effect of waning immunity and whole-cell vaccine priming.

METHODS

We used the test-negative design, a nested case-control study with test-negative individuals as controls. We constructed multivariable logistic regression models to estimate odds ratios (ORs). Vaccine effectiveness was calculated as (1 - OR) × 100. We assessed waning immunity by calculating the odds of developing pertussis per year since last vaccination and evaluated the relative effectiveness of priming with acellular versus whole-cell vaccine.

RESULTS

Between Dec. 7, 2009, and Mar. 31, 2013, data on 5867 individuals (486 test-positive cases and 5381 test-negative controls) were available for analysis. Adjusted vaccine effectiveness was 80% (95% confidence interval [CI] 71% to 86%) at 15-364 days, 84% (95% CI 77% to 89%) at 1-3 years, 62% (95% CI 42% to 75%) at 4-7 years and 41% (95% CI 0% to 66%) at 8 or more years since last vaccination. We observed waning immunity with the acellular vaccine, with an adjusted OR for pertussis infection of 1.27 (95% CI 1.20 to 1.34) per year since last vaccination. Acellular, versus whole-cell, vaccine priming was associated with an increased odds of pertussis (adjusted OR 2.15, 95% CI 1.30 to 3.57).

INTERPRETATION

We observed high early effectiveness of the pertussis vaccine that rapidly declined as time since last vaccination surpassed 4 years, particularly with acellular vaccine priming. Considering whole-cell vaccine priming and/or boosters in pregnancy to optimize pertussis control may be prudent.