Acellular pertussis vaccines in Japan: past, present and future

"I Want People to Be Able to Make an Informed Choice": How Quebec naturopaths discuss vaccination in their practice

Health care providers' recommendations can play an important role in individuals' vaccination decisions. Despite being one of the most popular complementary and alternative medicine (CAM), naturopathy is understudied in relation to vaccination decisions. We sought to address this gap through this study of vaccination perspectives of naturopathy practitioners in the province of Quebec, Canada. We conducted in-depth interviews with 30 naturopaths. Thematic analysis was conducted. Main themes were developed deductively (i.e., based on prior literature) and expanded through inductive coding of the data. Participants noted that they discuss vaccination in their practice, but only when clients asked questions or wanted advice. Naturopaths described refraining from explicitly recommending for or against vaccination. Instead, they focus on empowering their clients to make their own informed decision regarding vaccination. Most participants noted that they direct clients towards sources of information so that clients could decide for themselves, but some mentioned they discussed with clients what they considered to be risks associated with vaccination, as well as its benefits. These discussions were framed through a personalized and individual approach with clients.

Attitude towards Intranasal Vaccines and Psychological Determinants: Effects on the General Population in Northern Italy

Little is known about the use of intranasal vaccines, but some studies have shown that this innovative way of administration is preferred over needle injection as it is considered both less painful and intrusive to the body, equally effective, and associated with fewer side effects. This study aimed to investigate specific psychological determinants (intolerance of uncertainty, persecutory ideation, perceived control, vaccine hesitancy) of attitude toward nasal vaccine delivery. A convenience sample including 700 Italian participants took part in this cross-sectional study and completed an online questionnaire. A structural equation model with a latent variable was performed to study the relationship between psychological variables, vaccine hesitancy, and attitude toward nasal vaccine delivery. The results indicate that both a hesitant attitude toward vaccination (β = 0.20, p = 0.000) and low perceived control (β = -0.20, p = 0.005) may directly increase preference for nasal administration; furthermore, high levels of persecutory ideation may indirectly influence the propensity for intranasal vaccine. These findings suggest that pharmaceutical companies could implement nasal vaccines and provide detailed information on these vaccines through informational campaigns. Hesitant individuals with low levels of perceived control could more easily comply with these types of vaccines.

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.

Development of carbohydrate based next-generation anti-pertussis vaccines

Pertussis is a highly contagious respiratory disease caused by the Gram-negative bacterial pathogen, Bordetella pertussis. Despite high global vaccination rates, pertussis is resurging worldwide. Here we discuss the development of current pertussis vaccines and their limitations, which highlight the need for new vaccines that can protect against the disease and prevent development of the carrier state, thereby reducing transmission. The lipo-oligosaccharide of Bp is an attractive antigen for vaccine development as the anti-glycan antibodies could have bactericidal activities. The structure of the lipo-oligosaccharide has been determined and its immunological properties analyzed. Strategies enabling the expression, isolation, and bioconjugation have been presented. However, obtaining the saccharide on a large scale with high purity remains one of the main obstacles. Chemical synthesis provides a complementary approach to accessing the carbohydrate epitopes in a pure and structurally well-defined form. The first total synthesis of the non-reducing end pertussis pentasaccharide is discussed. The conjugate of the synthetic glycan with a powerful immunogenic carrier, bacteriophage Qβ, results in high levels and long-lasting anti-glycan IgG antibodies, paving the way for the development of a new generation of anti-pertussis vaccines with high bactericidal activities and biocompatibilities.

Whole-Cell and Acellular Pertussis Vaccine: Reflections on Efficacy

Pertussis is a common respiratory infection caused by the bacterium Bordetella pertussis. Although most cases occur in developing countries, it is considered endemic globally. The World Health Organization estimates there are 20-40 million cases of pertussis annually. Pertussis vaccines played a pivotal role in reducing the burden of pertussis disease as well as infant morbidity and mortality. Although the two forms of pertussis vaccine are effective, each has its advantages and drawbacks. This review aims to review the current knowledge on pertussis vaccines, emphasizing vaccine effectiveness in different populations within a community. Clinical trials have shown favorable vaccine efficacy with acellular pertussis (aP)vaccine. However, observational and population-level studies showed that introducing at least a single dose of whole-cell pertussis (wP) vaccine within the routine immunization schedule is associated with better disease protection and a longer duration of immunity. On the other hand, wP vaccine is more reactogenic and associated with higher adverse events. Therefore, the selection of vaccine should be weighed against the effectiveness, reactogenicity, and cost-effectiveness. Due to its safety profile, aP vaccine can be offered to wider population groups. Booster adolescent and pregnant immunization programs have been implemented globally to control outbreaks and protect vulnerable infants. Due to the variable effectiveness performance of both vaccines, different countries adopted distinctive immunization programs. Determining the right vaccination approach depends on financial consideration, immunization program infrastructure, adverse event monitoring, and pertussis surveillance in the community.

Molecular Epidemiology of Bordetella pertussis

Although vaccination has been effective, Bordetella pertussis is increasingly causing epidemics, especially in industrialized countries using acellular vaccines (aPs). One factor behind the increased circulation is the molecular changes on the pathogen level. After pertussis vaccinations were introduced, changes in the fimbrial (Fim) serotype of the circulating strains was observed. When bacterial typing methods improved, further changes between the vaccine and circulating strains, especially among the common virulence genes including pertussis toxin (PT) and pertactin (PRN) were noticed. Moreover, development of genome based techniques including pulsed-field gel electrophoresis (PFGE), multiple-locus variable number tandem repeat analysis (MLVA) and whole-genome sequencing (WGS) have offered a better resolution to monitor B. pertussis strains. After the introduction of aP vaccines, B. pertussis strains that are deficient to vaccine antigens, especially PRN, have appeared widely. On the other hand, antimicrobial resistance to first line drugs (macrolides) against B. pertussis is still low in many countries and therefore no globally evaluated antimicrobial susceptibility test values have been recommended. In this review, we focus on the molecular changes in the bacteria, which have or may have affected the past and current epidemiology of pertussis.

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.

Recommendations and barriers to vaccination in systemic lupus erythematosus

Patients with Systemic Lupus Erythematosus (SLE) pose a unique dilemma pertaining to immunization against common pathogens. SLE patients are usually not immunized with vaccines based on the fear of either precipitating infection in this immunosuppressed patient population (with live vaccines) or aggravating autoimmunity and hence lupus flares (with any vaccines). However, elevated vulnerability to infection makes patients with SLE precisely the population that needs protection from vaccine-preventable diseases. A summary of guidelines from the Centers for Disease Control and Prevention, professional societies, review articles and expert opinions regarding use of individual vaccines applicable to adults with SLE is presented in this review.

Safety testing of acellular pertussis vaccines: Use of animals and 3Rs alternatives

The current test of acellular Bordetella pertussis (aP) vaccines for residual pertussis toxin (PTx) is the Histamine Sensitization test (HIST), based on the empirical finding that PTx sensitizes mice to histamine. Although HIST has ensured the safety of aP vaccines for years, it is criticized for the limited understanding of how it works, its technical difficulty, and for animal welfare reasons. To estimate the number of mice used worldwide for HIST, we surveyed major aP manufacturers and organizations performing, requiring, or recommending the test. The survey revealed marked regional differences in regulatory guidelines, including the number of animals used for a single test. Based on information provided by the parties surveyed, we estimated the worldwide number of mice used for testing to be 65,000 per year: ∼48,000 by manufacturers and ∼17,000 by national control laboratories, although the latter number is more affected by uncertainty, due to confidentiality policies. These animals covered the release of approximately 850 final lots and 250 in-process lots of aP vaccines yearly. Although there are several approaches for HIST refinement and reduction, we discuss why the efforts needed for validation and implementation of these interim alternatives may not be worthwhile, when there are several in vitro alternatives in various stages of development, some already fairly advanced. Upon implementation, one or more of these replacement alternatives can substantially reduce the number of animals currently used for the HIST, although careful evaluation of each alternative's mechanism and its suitable validation will be necessary in the path to implementation.

A postpartum vaccination promotion intervention using motivational interviewing techniques improves short-term vaccine coverage: PromoVac study

BACKGROUND

Due to the increasing number of vaccine-hesitant parents, new effective immunization promotion strategies need to be developed to improve the vaccine coverage (VC) of infants. This study aimed to assess the impact of an educational strategy of vaccination promotion based on motivational interviewing (MI) techniques targeting parents and delivered at the maternity ward, for the VC of infants at 3, 5, and 7 months of age.

METHODS

An individual educational information session, administered using MI techniques, regarding immunization of infants aged 2, 4, and 6 months was (experimental group) or was not (control group) proposed to parents during the postpartum stay at the maternity ward. Immunization data were obtained through the Eastern Townships Public Health registry for infants at 3, 5, and 7 months of age. Absolute VC increases at 3, 5, and 7 months in the experimental group were calculated and the relative risks with the respective 95% confidence intervals were computed using univariate logistic regression with the generalized estimating equations (GEE) procedure. Multivariate regression using GEE was used to adjust for confounding variables.

RESULTS

In the experimental and control groups, 1140 and 1249 newborns were included, respectively. A significant increase in VC of 3.2, 4.9, and 7.3% was observed at 3, 5, and 7 months of age (P < 0.05), respectively. The adjusted relative risk of the intervention's impact on vaccination status at 7 months of age was 1.08 (95% confidence interval: 1.03-1.14) (P = 0.002).

CONCLUSIONS

An educational strategy using MI techniques delivered at the maternity ward may be effective in increasing VC of infants at ages 3, 5, and 7 months. MI could be an effective tool to overcome vaccine hesitancy.

Protective effects of in vivo-expressed autotransporters against Bordetella pertussis infection

Bordetella pertussis causes whooping cough, a severe and prolonged respiratory disease that results inhas high morbidity and mortality rates, particularly in developing countries. The number incidence of whooping cough cases is increasing in many countries despite high vaccine coverage. Causes for the re-emergence of the disease include the limited duration of protection conferred by the acellular pertussis vaccines (aP)s and pathogenic adaptations that involve antigenic divergence from vaccine strains. Therefore, current vaccines therefore need to be improved. In the present study, we focused on five autotransporters: namely SphB1, BatB, SphB2, Phg, and Vag8, which were previously found to be expressed by B. bronchiseptica during the course of infection in rats and examined their protective efficiencies as vaccine antigens. The passenger domains of these proteins were produced in recombinant forms and used as antigens. An intranasal murine challenge assay showed that immunization with a mixture of SphB1 and Vag8 (SV) significantly reduced bacterial load in the lower respiratory tract and a combination of aP and SV acts synergistically in effects of conferring protection against B. pertussis infection, implying that these antigens have potential as components to for improvinge th the currently available acellular pertussis vaccine.

Bordetella pertussis population dynamics and phylogeny in Japan after adoption of acellular pertussis vaccines

Bordetella pertussis, the causative agent of whooping cough, has experienced a resurgence in the past 15 years, despite the existence of both whole-cell and acellular vaccines. Here, we performed whole genome sequencing analysis of 149 clinical strains, provided by the National Institute of Infectious Diseases (NIID), Japan, isolated in 1982–2014, after Japan became the first country to adopt acellular vaccines against B. pertussis. Additionally, we sequenced 39 strains provided by the Konan Kosei Hospital in Aichi prefecture, Japan, isolated in 2008–2013. The genome sequences afforded insight into B. pertussis genome variability and population dynamics in Japan, and revealed that the B. pertussis population in Japan was characterized by two major clades that divided more than 40 years ago. The pertactin gene was disrupted in about 20 % of the 149 NIID isolates, by either a deletion within the signal sequence (ΔSS) or the insertion of IS element IS481 (prn :: IS481). Phylogeny suggests that the parent clones for these isolates originated in Japan. Divergence dating traced the first generation of the pertactin-deficient mutants in Japan to around 1990, and indicated that strains containing the alternative pertactin allele prn2 may have appeared in Japan around 1974. Molecular clock data suggested that observed fluctuations in B. pertussis population size may have coincided with changes in vaccine usage in the country. The continuing failure to eradicate the disease warrants an exploration of novel vaccine compositions.

The relationship between mucosal immunity, nasopharyngeal carriage, asymptomatic transmission and the resurgence of Bordetella pertussis

The incidence of whooping cough in the US has been rising slowly since the 1970s, but the pace of this has accelerated sharply since acellular pertussis vaccines replaced the earlier whole cell vaccines in the late 1990s. A similar trend occurred in many other countries, including the UK, Canada, Australia, Ireland, and Spain, following the switch to acellular vaccines. The key question is why. Two leading theories (short duration of protective immunologic persistence and evolutionary shifts in the pathogen to evade the vaccine) explain some but not all of these shifts, suggesting that other factors may also be important.

In this synthesis, we argue that sterilizing mucosal immunity that blocks or abbreviates the duration of nasopharyngeal carriage of Bordetella pertussis and impedes person-to-person transmission (including between asymptomatically infected individuals) is a critical factor in this dynamic. Moreover, we argue that the ability to induce such mucosal immunity is fundamentally what distinguishes whole cell and acellular pertussis vaccines and may be pivotal to understanding much of the resurgence of this disease in many countries that adopted acellular vaccines. Additionally, we offer the hypothesis that observed herd effects generated by acellular vaccines may reflect a modification of disease presentation leading to reduced potential for transmission by those already infected, as opposed to inducing resistance to infection among those who have been exposed.

Understanding Vaccine Hesitancy in Canada: Results of a Consultation Study by the Canadian Immunization Research Network

"Vaccine hesitancy" is a concept now frequently used in vaccination discourse. The increased popularity of this concept in both academic and public health circles is challenging previously held perspectives that individual vaccination attitudes and behaviours are a simple dichotomy of accept or reject. A consultation study was designed to assess the opinions of experts and health professionals concerning the definition, scope, and causes of vaccine hesitancy in Canada. We sent online surveys to two panels (1- vaccination experts and 2- front-line vaccine providers). Two questionnaires were completed by each panel, with data from the first questionnaire informing the development of questions for the second. Our participants defined vaccine hesitancy as an attitude (doubts, concerns) as well as a behaviour (refusing some / many vaccines, delaying vaccination). Our findings also indicate that both vaccine experts and front-line vaccine providers have the perception that vaccine rates have been declining and consider vaccine hesitancy an important issue to address in Canada. Diffusion of negative information online and lack of knowledge about vaccines were identified as the key causes of vaccine hesitancy by the participants. A common understanding of vaccine hesitancy among researchers, public health experts, policymakers and health care providers will better guide interventions that can more effectively address vaccine hesitancy within Canada.

Seroprevalence studies of pertussis: what have we learned from different immunized populations

Bordetella pertussis is a pathogen-causing whooping cough (pertussis) in humans. Although vaccination against the disease is effective, the bacterium is still circulating among population and can even cause death. Especially young infants, who lack protection, are vulnerable. The laboratory diagnostic methods to detect B. pertussis are culture, PCR and ELISA serology. Reported cases of the disease vary among countries but usually the incidence rates are low, <1 to 10/100 000. However, pertussis often goes unrecognized among patients as it presents itself like the common cold, especially in adults and elders who are often the source of the infection. This makes pertussis difficult to monitor and control. Serological surveillance is an easy manner to estimate the real burden of the disease among population. Furthermore, to have reliable results, anti-PT IgG antibodies should be measured, as PT is the only specific antigen to B. pertussis. This review aims to evaluate available pertussis seroprevalence studies throughout the world, and to compare the findings from countries with different vaccination histories and strategies. Estimation of the real burden of pertussis is compared to reported numbers. In addition, future aspects in seroprevalence studies are considered.

Assessment of antibody level and avidity against Bordetella pertussis in a cohort of Egyptian individuals aged 1-18 years

Pertussis specific antibodies were studied with respect to quality and quantity in a cohort of apparently healthy Egyptian children and adolescents, with their age range between 1 and 18 years, in an attempt to get a close and clear insight into the current humoral immunization status in this specified group and to try find a relation between the antibody levels and their avidities in eradication of this devastating infectious disease. Our results showed that avidity increase was most marked in young school children (6–8 years) where it seemed to reach a plateau in older children and adolescents. Antibody titer was highest in toddlers (1–2 years) and young school children (6–8 years) groups, most probably following vaccination and/or booster doses. Among children aged 1–5 years, 28% had highly avid and 50% had high titer antibodies, whereas in adolescents aged 13–18 years, 70% had highly avid antibodies and only 30% had high titer antibodies. The results clearly demonstrated that while levels of anti-Bordetella pertussis (B. pertussis) antibodies wane with growing age, the avidity seems to increase, to a plateau, irrespective of further antigen exposure in a pattern showing complete independence of avidity on concentration. The present study draws attention to the importance of avidity measurements, together with conventional ELISAs, for evaluating immunity against pertussis. Being based on a limited sample size, it could open doors for larger-scale surveys to be possible indicators for the need and timing of booster vaccination doses among Egyptians.

Vaccine hesitancy, vaccine refusal and the anti-vaccine movement: influence, impact and implications

Despite being recognized as one of the most successful public health measures, vaccination is perceived as unsafe and unnecessary by a growing number of parents. Anti-vaccination movements have been implicated in lowered vaccine acceptance rates and in the increase in vaccine-preventable disease outbreaks and epidemics. In this review, we will look at determinants of parental decision-making about vaccination and provide an overview of the history of anti-vaccination movements and its clinical impact.

The first steps towards the era of personalised vaccinology: predicting adverse reactions

Until now, the occurrence of adverse reactions among individuals inoculated with identical vaccines has been ascribed to unpredictable stochastic processes. Recent advances in pharmacogenomics indicate that some features of host response to immunisation are influenced by genetic traits, henceforth predictable. The ability to predict the adverse reaction to vaccination would represent an important step towards the development of personalised vaccinology and could enhance public confidence in the safety of vaccines. Herein, we have reviewed all the available information on the association between genetic variants and the risk for healthy subjects to develop adverse reactions.

Acellular vaccines for preventing whooping cough in children

BACKGROUND

Routine use of whole-cell pertussis (wP) vaccines was suspended in some countries in the 1970s and 1980s because of concerns about adverse effects. Following this action, there was a resurgence of whooping cough. Acellular pertussis (aP) vaccines, containing purified or recombinant Bordetella pertussis (B. pertussis) antigens, were developed in the hope that they would be as effective, but less reactogenic than the whole-cell vaccines. This is an update of a Cochrane review first published in 1999, and previously updated in 2012. In this update, we included no new studies.

OBJECTIVES

To assess the efficacy and safety of acellular pertussis vaccines in children and to compare them with the whole-cell vaccines.

SEARCH METHODS

We searched CENTRAL (2013, Issue 12), MEDLINE (1950 to January week 2, 2014), EMBASE (1974 to January 2014), Biosis Previews (2009 to January 2014) and CINAHL (2009 to January 2014).

SELECTION CRITERIA

We selected double-blind randomised efficacy and safety trials of aP vaccines in children up to six years old, with active follow-up of participants and laboratory verification of pertussis cases.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the risk of bias in the studies. Differences in trial design precluded a meta-analysis of the efficacy data. We pooled the safety data from individual trials using a random-effects meta-analysis model.

MAIN RESULTS

We included six efficacy trials with a total of 46,283 participants and 52 safety trials with a total of 136,541 participants. Most of the safety trials did not report the methods for random sequence generation, allocation concealment and blinding, which made it difficult to assess the risk of bias in the studies. The efficacy of multi-component (≥ three) vaccines varied from 84% to 85% in preventing typical whooping cough (characterised by 21 or more consecutive days of paroxysmal cough with confirmation of B. pertussis infection by culture, appropriate serology or contact with a household member who has culture-confirmed pertussis), and from 71% to 78% in preventing mild pertussis disease (characterised by seven or more consecutive days of cough with confirmation of B. pertussis infection by culture or appropriate serology). In contrast, the efficacy of one- and two-component vaccines varied from 59% to 78% against typical whooping cough and from 41% to 58% against mild pertussis disease. Multi-component acellular vaccines are more effective than low-efficacy whole-cell vaccines, but may be less effective than the highest-efficacy whole-cell vaccines. Most systemic and local adverse events were significantly less common with aP vaccines than with wP vaccines for the primary series as well as for the booster dose.

AUTHORS' CONCLUSIONS

Multi-component (≥ three) aP vaccines are effective in preventing whooping cough in children. Multi-component aP vaccines have higher efficacy than low-efficacy wP vaccines, but they may be less efficacious than the highest-efficacy wP vaccines. Acellular vaccines have fewer adverse effects than whole-cell vaccines for the primary series as well as for booster doses.

Acellular pertussis vaccines in China

In China, whole-cell pertussis (Pw) vaccines were produced in the early 1960s and acellular pertussis (Pa) vaccines were introduced in 1995. Pa vaccines have now almost completely replaced Pw vaccines in the national immunization program. To strengthen the regulation of vaccines used in China, a vaccine lot release system was established in 2001 and Pa vaccines have been included in the system since 2006. This paper mainly described the current status of production and the quality control measures in place for Pa vaccines; and analyses quality control test data accumulated between 2006 and 2010.

Acellular vaccines for preventing whooping cough in children

BACKGROUND

Routine use of whole-cell pertussis (wP) vaccines was suspended in some countries in the 1970s and 1980s because of concerns about adverse effects. Following such action, there was a resurgence of whooping cough. Acellular pertussis (aP) vaccines, containing purified or recombinant Bordetella pertussis (B. pertussis) antigens, were developed in the hope that they would be as effective, but less reactogenic than the whole-cell vaccines.

OBJECTIVES

To assess the efficacy and safety of acellular pertussis vaccines in children.

SEARCH METHODS

We searched the Cochrane Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 4) which contains the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (1950 to December week 4, 2011), EMBASE (1974 to January 2012), Biosis Previews (2009 to January 2012), and CINAHL (2009 to January 2012).

SELECTION CRITERIA

We selected double-blind randomised efficacy and safety trials of aP vaccines in children up to six years old, with active follow-up of participants and laboratory verification of pertussis cases.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the risk of bias in the studies. Differences in trial design precluded a meta-analysis of the efficacy data. We pooled the safety data from individual trials using a random-effects meta-analysis model.

MAIN RESULTS

We included six efficacy trials with a total of 46,283 participants and 52 safety trials with a total of 136,541 participants. Most of the safety trials did not report the methods for random sequence generation, allocation concealment and blinding, which made it difficult to assess the risk of bias in the studies. The efficacy of multi-component (≥ three) vaccines varied from 84% to 85% in preventing typical whooping cough (characterised by 21 or more consecutive days of paroxysmal cough with confirmation of B. pertussis infection by culture, appropriate serology or contact with a household member who has culture-confirmed pertussis), and from 71% to 78% in preventing mild pertussis disease (characterised by seven or more consecutive days of cough with confirmation of B. pertussis infection by culture or appropriate serology). In contrast, the efficacy of one- and two-component vaccines varied from 59% to 75% against typical whooping cough and from 13% to 54% against mild pertussis disease. Multi-component acellular vaccines are more effective than low-efficacy whole-cell vaccines, but may be less effective than the highest-efficacy whole-cell vaccines. Most systemic and local adverse events were significantly less common with aP vaccines than with wP vaccines for the primary series as well as for the booster dose.

AUTHORS' CONCLUSIONS

Multi-component (≥ three) aP vaccines are effective and show less adverse effects than wP vaccines for the primary series as well as for booster doses.

Acellular vaccines for preventing whooping cough in children

BACKGROUND

Routine use of whole-cell pertussis vaccines was suspended in some countries in the 1970s/1980s because of concerns about adverse effects. There was a resurgence of whooping cough. Acellular pertussis vaccines (containing purified or recombinant Bordetella pertussis antigens) were developed in the hope that they would be as effective but less reactogenic than the whole-cell vaccines.

OBJECTIVES

To assess the efficacy and safety of acellular pertussis vaccines in children.

SEARCH STRATEGY

We searched the Cochrane Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, issue 2) which contains the Acute Respiratory Infections Group's Specialised Register; MEDLINE (1950 to April week 2 2009) and EMBASE (1974 to April 2009).

SELECTION CRITERIA

Double-blind randomised efficacy and safety trials of acellular pertussis vaccines in children up to six years old, with active follow-up of participants and laboratory verification of pertussis cases.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed data extraction and study quality assessment. Differences in trial design precluded pooling of the efficacy data. The safety data from individual trials were pooled using the Cochrane statistical package Review Manager 5.

MAIN RESULTS

Six efficacy trials and 52 safety trials were included. The efficacy of multi-component (≥ 3) vaccines varied from 84% to 85% in preventing typical whooping cough, and from 71% to 78% in preventing mild pertussis disease. In contrast, the efficacy of one- and two-component vaccines varied from 59% to 75% against typical whooping cough, and from 13% to 54% against mild pertussis disease. Multi-component acellular vaccines is more effective than low-efficacy whole-cell vaccines, but may be less effective than the highest-efficacy whole-cell vaccines. Most systemic and local adverse events were significantly less common with acellular than with whole-cell pertussis vaccines for the primary series as well as for the booster dose.

AUTHORS' CONCLUSIONS

Multi-component acellular pertussis vaccines are effective, and show less adverse effects than whole-cell pertussis vaccines for the primary series as well as for booster doses.

Safe and effective booster immunization using DTaP in teenagers

The incidence of reported cases with pertussis has increased in young adults in Japan and the lack of additional booster immunizations containing pertussis components is suspected to be one of the causal reasons. Instead of DT immunization at 11-12 years of age, safety and immunogenicity were investigated using 0.2 ml and 0.5 ml of DTaP. 176 subjects in DTaP 0.5ml, 178 in DTaP 0.2 ml, and 197 in DT 0.1 ml groups were enrolled in clinical trial. The relative risk of local reactions in the DTaP 0.2 ml group compared to the DT 0.1 ml group was 1.13 (95% CI: 0.97-1.30), and that of the DTaP 0.5 ml to the DT 0.1 ml group was 1.34 (95% CI: 1.18-1.53). The relative risks of local pain and heat were 1.62 (95% CI: 1.33-1.98) and 1.59 (95% CI: 1.19-2.13), respectively, in the DTaP 0.5 ml group compared to the DT 0.1 ml group. Sero-positive rates against PT and FHA were 54% and 82% before immunization and increased to >95% for both after vaccination with no significant difference in GMT. Instead of the scheduled DT program, 0.2 ml of DTaP was acceptable and demonstrated efficient immunogenicity.

Impact of vaccination and birth rate on the epidemiology of pertussis: a comparative study in 64 countries

Bordetella pertussis infection remains an important public health problem worldwide despite decades of routine vaccination. A key indicator of the impact of vaccination programmes is the inter-epidemic period, which is expected to increase with vaccine uptake if there is significant herd immunity. Based on empirical data from 64 countries across the five continents over the past 30-70 years, we document the observed relationship between the average inter-epidemic period, birth rate and vaccine coverage. We then use a mathematical model to explore the range of scenarios for duration of immunity and transmission resulting from repeat infections that are consistent with empirical evidence. Estimates of pertussis periodicity ranged between 2 and 4.6 years, with a strong association with susceptible recruitment rate, defined as birth rate × (1 - vaccine coverage). Periodicity increased by 1.27 years on average after the introduction of national vaccination programmes (95% CI: 1.13, 1.41 years), indicative of increased herd immunity. Mathematical models suggest that the observed patterns of pertussis periodicity are equally consistent with loss of immunity that is not as rapid as currently thought, or with negligible transmission generated by repeat infections. We conclude that both vaccine coverage and birth rate drive pertussis periodicity globally and that vaccination induces strong herd immunity effects. A better understanding of the role of repeat infections in pertussis transmission is critical to refine existing control strategies.

Changes in the genomic content of circulating Bordetella pertussis strains isolated from the Netherlands, Sweden, Japan and Australia: adaptive evolution or drift?

Background

Bordetella pertussis is the causative agent of human whooping cough (pertussis) and is particularly severe in infants. Despite worldwide vaccinations, whooping cough remains a public health problem. A significant increase in the incidence of whooping cough has been observed in many countries since the 1990s. Several reasons for the re-emergence of this highly contagious disease have been suggested. A particularly intriguing possibility is based on evidence indicating that pathogen adaptation may play a role in this process. In an attempt to gain insight into the genomic make-up of B. pertussis over the last 60 years, we used an oligonucleotide DNA microarray to compare the genomic contents of a collection of 171 strains of B. pertussis isolates from different countries.

Results

The CGH microarray analysis estimated the core genome of B. pertussis, to consist of 3,281 CDSs that are conserved among all B. pertussis strains, and represent 84.8% of all CDSs found in the 171 B. pertussis strains. A total of 64 regions of difference consisting of one or more contiguous CDSs were identified among the variable genes. CGH data also revealed that the genome size of B. pertussis strains is decreasing progressively over the past 60 years. Phylogenetic analysis of microarray data generated a minimum spanning tree that depicted the phylogenetic structure of the strains. B. pertussis strains with the same gene content were found in several different countries. However, geographic specificity of the B. pertussis strains was not observed. The gene content was determined to highly correlate with the ptxP-type of the strains.

Conclusions

An overview of genomic contents of a large collection of isolates from different countries allowed us to derive a core genome and a phylogenetic structure of B. pertussis. Our results show that B. pertussis is a dynamic organism that continues to evolve.

Production and characterization of recombinant pertactin, fimbriae 2 and fimbriae 3 from Bordetella pertussis

BACKGROUND

Bordetella pertussis is a causative agent of pertussis or whooping cough in humans. Pertactin (Prn), fimbriae 2 (Fim2) and fimbriae 3 (Fim3) of B. pertussis are important virulence factors and immunogens which have been included in some acellular pertussis vaccines. In this present study, we cloned, expressed and purified Prn, Fim2 and Fim3, respectively. The immunogenicity and protective efficacy of the three recombinant proteins (rPrn, rFim2 and rFim3) were investigated in mouse model.

RESULTS

Three recombinant proteins with amount of 12 to 25 mg/L were produced. Compared to the control mice only immunized with adjuvant, serum IgG antibody responses were significantly induced in the mice immunized with rPrn, rFim2 or rFim3 (P < 0.001 for all three proteins). Furthermore, T cell responses characteristic of increased production of IL-2 and TNF-alpha (only for rPrn) were elicited in the mice immunized with the three proteins (P < 0.05 for all three proteins). Immunization with rPrn, but not with rFim2 or rFim3, significantly enhanced clearance of bacteria in the lungs of mice after intranasal challenge with B. pertussis (P < 0.05). When tested in a lethal intracerebral infection model, certain protection was observed in mice immunized with rPrn.

CONCLUSIONS

We have developed an efficient method to produce large amounts of rPrn, rFim2, and rFim3 from B. pertussis. The three recombinant proteins induced both humoral and cellular immune responses in mice. Immunization with rPrn also conferred protection against pertussis in mouse infection models. Our results indicated that the recombinant proteins still retain their immunological properties and highlighted the potential of the recombinant proteins for the future development of the B. pertussis vaccines.

Global trends and challenges in vaccine safety

Although vaccines are among the most effective public health interventions, safe delivery of safe vaccines is a priority in order to maintain public confidence and obtain maximum public health benefit. In order to assure that the vaccines we use are safe, adequate vaccine safety assessment is required on a global level. The purpose of this article is to review the current vaccine safety infrastructure, to identify deficits in the current systems and to identify approaches to improving the current infrastructure.

The epidemiology of pertussis in Germany: past and present

BACKGROUND

Current and past pertussis epidemiology in the two parts of Germany is compared in the context of different histories of vaccination recommendations and coverage to better understand patterns of disease transmission.

METHODS

Available regional pertussis surveillance and vaccination coverage data, supplemented by a literature search for published surveys as well as official national hospital and mortality statistics, were analyzed in the context of respective vaccination recommendations from 1964 onwards.

RESULTS

Routine childhood pertussis vaccination was recommended in the German Democratic Republic (GDR) from 1964 and in former West German states (FWG) from 1969, but withdrawn from 1974-1991 in FWG. Pertussis incidence declined to <1 case/100,000 inhabitants in GDR prior to reunification in 1991, while in FWG, where pertussis was not notifiable after 1961, incidence was estimated at 160-180 cases/100,000 inhabitants in the 1970s-1980s. Despite recommendations for universal childhood immunization in 1991, vaccination coverage decreased in former East German States (FEG) and increased only slowly in FWG. After introduction of acellular pertussis vaccines in 1995, vaccination coverage increased markedly among younger children, but remains low in adolescents, especially in FWG, despite introduction of a booster vaccination for 9-17 year olds in 2000. Reported pertussis incidence increased in FEG to 39.3 cases/100,000 inhabitants in 2007, with the proportion of adults increasing from 20% in 1995 to 68% in 2007. From 2004-2007, incidence was highest among 5-14 year-old children, with a high proportion fully vaccinated according to official recommendations, which did not include a preschool booster until 2006. Hospital discharge statistics revealed a ~2-fold higher pertussis morbidity among infants in FWG than FEG.

CONCLUSION

The shift in pertussis morbidity to older age groups observed in FEG is similar to reports from other countries with longstanding vaccination programs and suggests that additional booster vaccination may be necessary beyond adolescence. The high proportion of fully vaccinated cases in older children in FEG suggests waning immunity 5-10 years after primary immunisation in infancy. The higher incidence of pertussis hospitalisations in infants suggests a stronger force of infection in FWG than FEG. Nationwide pertussis reporting is required for better evaluation of transmission patterns and vaccination policy in both parts of Germany.

WITHDRAWN: Acellular vaccines for preventing whooping cough in children

BACKGROUND

Routine use of whole cell pertussis vaccines was suspended in some countries in the late 1970s and early 1980s, leading to a resurgence of whooping cough. Acellular pertussis vaccines containing purified or recombinant Bordetella pertussis antigens were developed in the hope that they would be as effective but less toxic than the whole cell vaccines.

OBJECTIVES

The objective of this review was to assess the effects of acellular pertussis vaccines in children.

SEARCH STRATEGY

The Cochrane Controlled Trials Register and Medline were searched up to January 1998.

SELECTION CRITERIA

Double-blind randomised efficacy and safety trials of acellular pertussis vaccines in children, with active follow-up of participants and laboratory verification of pertussis cases.

DATA COLLECTION AND ANALYSIS

One reviewer assessed trial quality and extracted data.

MAIN RESULTS

Six efficacy trials and 45 safety trials were included. Acellular pertussis vaccines with three or more pertussis vaccines were more effective than those with one or two antigens. They were also more effective than one type of whole cell pertussis vaccine, but less effective than two other types of whole cell vaccines. Differences in trial design precluded pooling of the efficacy data and results should be interpreted with caution. Most systemic and local adverse events were significantly less common with acellular than with whole cell pertussis vaccines.

AUTHORS' CONCLUSIONS

Multi-component acellular pertussis vaccines are effective, and show less adverse effects than whole cell pertussis vaccines. However in areas where whooping cough is more likely to be fatal, the higher toxicity of some whole cell vaccines may be offset by their increased effectiveness.