Can vaccines control bacterial virulence and pathogenicity? Bordetella pertussis: the advantage of fitness over virulence

Some vaccines, such as diphtheria toxoid and acellular pertussis vaccines (aPVs), may favor the emergence of less pathogenic strains of the respective bacteria they target. This review discusses the impact of the wide use of aPV on Bordetella pertussis phenotype evolutions and their beneficial consequences in the light of the diphtheria toxoid immunization program experience and structuring evidence review in a causal analysis following Bradford Hill’s causality criteria. All aPVs contain the pertussis toxin (PT), the main virulence factor of B.pertussis, alone or with one adhesin (filamentous hemagglutinin (FHA)), two adhesins (FHA and pertactin (PRN)) or four adhesins (FHA, PRN and two fimbriae (Fim 2/3)). In countries where the coverage of aPVs containing PRN is high, PRN negative B.pertussis isolates are increasing in prevalence, but isolates nonproducing the other antigens are rarely reported. We hypothesize that the selective pressure at play with PRN should exist against all aVP antigens, although detection biases may hinder its detection for other antigens, especially PT. PT being responsible for clinically frank cases of the disease, the opportunity to collect PT negative isolates is far lower than to collect PRN negative isolates which have a limited clinical impact. The replacement of the current B.pertussis by far less pathogenic isolates no longer producing the factors contained in aPVs should be expected as a consequence of the wide aPV use.

Evolution of Bordetella pertussis over a 23-year period in France, 1996 to 2018

BackgroundBordetella pertussis is the main agent of whooping cough. Vaccination with acellular pertussis vaccines has been largely implemented in high-income countries. These vaccines contain 1 to 5 antigens: pertussis toxin (PT), filamentous haemagglutinin (FHA), pertactin (PRN) and/or fimbrial proteins (FIM2 and FIM3). Monitoring the emergence of B. pertussis isolates that might partially escape vaccine-induced immunity is an essential component of public health strategies to control whooping cough.AimWe aimed to investigate temporal trends of fimbriae serotypes and vaccine antigen-expression in B. pertussis over a 23-year period in France (1996-2018).MethodsIsolates (n = 2,280) were collected through hospital surveillance, capturing one third of hospitalised paediatric pertussis cases. We assayed PT, FHA and PRN production by Western blot (n = 1,428) and fimbriae production by serotyping (n = 1,058). Molecular events underlying antigen deficiency were investigated by genomic sequencing.ResultsThe proportion of PRN-deficient B. pertussis isolates has increased steadily from 0% (0/38) in 2003 to 48.4% (31/64) in 2018 (chi-squared test for trend, p < 0.0001), whereas only 5 PT-, 5 FHA- and 9 FIM-deficient isolates were found. Impairment of PRN production was predominantly due to IS481 insertion within the prn gene or a 22 kb genomic inversion involving the prn promoter sequence, indicative of convergent evolution. FIM2-expressing isolates have emerged since 2011 at the expense of FIM3.ConclusionsB. pertussis is evolving through the rapid increase of PRN-deficient isolates and a recent shift from FIM3 to FIM2 expression. Excluding PRN, the loss of vaccine antigen expression by circulating B. pertussis isolates is epidemiologically insignificant.

Pertussis epidemiology in Tunisian infants and children and characterization of Bordetella pertussis isolates: results of a 9-year surveillance study, 2007 to 2016

PURPOSE

Pertussis remains a public health concern in most countries. Our study aimed to prospectively explore the epidemiology of pertussis in the Tunis area of Tunisia between 2007 and 2016, and to characterize the virulence-associated genes of the collected Bordetella pertussis isolates.

METHODOLOGY

Infants and children hospitalized at the Children's Hospital of Tunis, Tunisia, between 2007 and 2016 for suspicion of pertussis were enrolled in the study. Culture and real-time PCR (qPCR) assays targeting IS481, IS1001, recA, H-IS1001 and ptxP were used to confirm the pertussis diagnosis. Phenotypic and genotypic characterization of recovered isolates was performed.Results/Key findings. A total of 1844 children were included in the study. Overall, 306 children (16.6 %) with Bordetella infection were confirmed by qPCR. Among them, 265 (86.6 %) were confirmed as having B. pertussis (IS481+, ptxP+, H-IS1001-), 18 (5.9 %) as having Bordetella parapertussis (IS481-, IS1001+) and 11 (3.6 %) as having Bordetella spp. (IS481+, ptxP-, H-IS1001-). No Bordetella holmesii (IS481+, IS1001-, H-IS1001+) was identified. The estimated pertussis incidence in the Tunis area was 134/100 000 in children aged less than 5 years. Two epidemic peaks were observed in 2009 and 2014. Ten B. pertussis isolates were cultured and characterized. Deficiency in pertactin expression was not observed, and genotyping of the isolates revealed a predominant allelic profile: ptxP3-ptxA1-prn2-fim2-1-fim3-2.

CONCLUSION

This study demonstrated that pertussis is still present as a cyclical disease in Tunisia, despite high primo-vaccination coverage with a pertussis whole-cell vaccine. The predominant genotype of Tunisian B. pertussis isolates is similar to isolates circulating in countries using the acellular vaccine.

Incidence of whooping cough in Spain (1997-2010): an underreported disease

Whooping cough is currently the worst controlled vaccine-preventable disease in the majority of countries. In order to reduce its morbidity and mortality, it is essential to adapt vaccination programmes to data provided by epidemiological surveillance. A population-based retrospective epidemiological study to estimate the minimum annual undernotification rate of pertussis in Spain from 1997 to 2010 was performed. The incidence of pertussis cases reported to the National Notifiable Disease Surveillance System was compared with the incidence of hospital discharges for pertussis from the National Surveillance System for hospital data, Conjunto Mínimo Básico de Datos. The overall reported incidence and that of hospitalisation for whooping cough were 1.3 cases × 100,000 inhabitants in both cases. Minimum underreporting oscillated between 3.8 and 22.8 %, according to the year of the study. The greatest underreporting (50 %) was observed in children under the age of 1 year.

CONCLUSION

Spanish epidemiological surveillance system of pertussis should be improved with complementary active systems to ascertain the real incidence. Paediatricians and general practitioners should be sensibilized to the importance of notification because this would be essential for adapting the prevention and control measures of this disease.

Antibody-mediated inhibition of Bordetella pertussis adenylate cyclase-haemolysin-induced macrophage cytotoxicity is influenced by variations in the bacterial population

Whooping cough is a vaccine-preventable disease presenting with epidemic cycles linked to natural and/or vaccine-driven evolution of the aetiological agent of the disease, Bordetella pertussis. Adenylate cyclase-haemolysin (AC-Hly) is a major toxin produced by this pathogen, which mediates macrophage apoptosis in vitro and in vivo. While current acellular pertussis vaccine (APV) formulations do not include AC-Hly, they all contain pertussis toxin and can comprise filamentous haemagglutinin (FHA), which interacts with AC-Hly, and pertactin (PRN), which has been hypothesized also to interact with AC-Hly. We aimed to study the capacity of specific antibodies to inhibit the in vitro B. pertussis AC-Hly-mediated cytotoxicity of J774A.1 murine macrophages in a background of a changing bacterial population. We demonstrate that: (i) clinical isolates of different types or PRN phenotype are all cytotoxic and lethal in the mouse model of respiratory infection; (ii) lack of PRN production does not impact AC-Hly-related phenotypes; (iii) anti-AC-Hly antibodies inhibit cell lysis whatever the phenotype of the isolate, while anti-PRN antibodies significantly inhibit cell lysis provided the isolate produces this antigen, which might be relevant in vivo for APV-induced immunity; and (iv) anti-FHA antibodies only inhibit lysis induced by isolates collected in 2012, maybe indicating specific characteristics of epidemic lineages of B. pertussis.

A cocoon immunisation strategy against pertussis for infants: does it make sense for Ontario?

Pertussis deaths occur primarily among infants who have not been fully immunised. In Ontario, Canada, an adult booster dose was recently added to the publicly funded immunisation programme. We applied number-needed-to-treat analyses to estimate the number of adults that would need to be vaccinated (NNV) to prevent pertussis disease, hospitalisation and death among infants if a cocoon strategy were implemented. NNV=1/(P(M) X R) + 1/(P(F) X R), where P(M),P(F) (proportion of infants infected by mothers, fathers) were sourced from several studies. Rates of disease, hospitalisation or death (R) were derived from Ontario's reportable disease data and Discharge Abstract Database. After adjusting for under-reporting, the NNV to prevent one case, hospitalisation or death from pertussis was between 500-6,400, 12,000-63,000 and 1.1-12.8 million, respectively. Without adjustment, NNV increased to 5,000-60,000, 55,000-297,000 and 2.5-30.2 million, respectively. Rarer outcomes were associated with higher NNV. These analyses demonstrate the relative inefficiency of a cocoon strategy in Ontario, which has a well-established universal immunisation programme with relatively high coverage and low disease incidence. Other jurisdictions considering a cocoon programme should consider their local epidemiology.

Virulence of pertactin-negative Bordetella pertussis isolates from infants, France

Bordetella pertussis isolates that do not express pertactin (PRN) are increasing in regions where acellular pertussis vaccines have been used for >7 years. We analyzed data from France and compared clinical symptoms among infants <6 months old infected by PRN-positive or PRN-negative isolates. No major clinical differences were found between the 2 groups.

Impact of postpartum information about pertussis booster to parents in a university maternity hospital

Parent-to-infant transmission of pertussis remains an issue in France. Although adult booster vaccination was introduced in 2004 as part of a cocooning strategy targeted primarily to parents of young infants, vaccination coverage in this population has remained low. The aim of this study was to evaluate the impact on vaccination coverage, over two consecutive years, of a protocol in which information about the pertussis booster and a prescription for pertussis vaccine were given to parents upon discharge from a French university maternity hospital. A questionnaire was administered to mothers two months after delivery, during two 3-month periods in 2008 and 2009. Participation rates were 67% (first period) and 76.3% (second period). Information about pertussis was delivered mainly by paediatricians and midwives and was considered clear and pertinent in more than 95% of cases. In 2009, 69% of mothers and 63% of fathers who received a prescription for pertussis vaccine before discharge from the maternity declared being vaccinated, with no difference as compared to 2008. Vaccination was done by a general practitioner (95.9%) and mostly in the first month after birth (81%). Postpartum information about pertussis was successfully implemented and well understood by parents in the maternity hospital and should contribute towards increasing pertussis vaccination coverage in parents of young children.

Potential impact of parental Tdap immunization on infant pertussis hospitalizations

We estimated the potential impact of parental Tdap immunization before delivery, at delivery and at the 2-week newborn visit on U.S. infant pertussis hospitalizations. We used published data for pertussis hospitalization rates among U.S. infants aged 0-4 months, the Tdap vaccine efficacy in adults, and the proportion of infants with pertussis <6 months of age in which either parent was the source (16-40% from mothers and 16-20% from fathers). Immunizing parents before pregnancy or ≥ 2 weeks prior to delivery should reduce pertussis hospitalizations among infants 0-4 months by 2694-9314 if both parents are vaccinated, and by 1347-6909 if only mothers are vaccinated. Greater reductions in pertussis hospitalizations would be achieved if parents are immunized ≥ 2 weeks prior to delivery than after delivery or the 2-week newborn visit. Although immunizing parents prior to pregnancy or delivery is best, immunizing parents in the postpartum period should provide protection to that newborn and to infants of subsequent pregnancies.

Evolution of French Bordetella pertussis and Bordetella parapertussis isolates: increase of Bordetellae not expressing pertactin

Bordetella pertussis and Bordetella parapertussis are closely related bacterial agents of whooping cough. Whole-cell pertussis (wP) vaccine was introduced in France in 1959. Acellular pertussis (aP) vaccine was introduced in 1998 as an adolescent booster and was rapidly generalized to the whole population, changing herd immunity by specifically targeting the virulence of the bacteria. We performed a temporal analysis of all French B. pertussis and B. parapertussis isolates collected since 2000 under aP vaccine pressure, using pulsed-field gel electrophoresis (PFGE), genotyping and detection of expression of virulence factors. Particular isolates were selected according to their different phenotype and PFGE type and their characteristics were analysed using the murine model of respiratory infection and in vitro cell cytotoxic assay. Since the introduction of the aP vaccines there has been a steady increase in the number of B. pertussis and B. parapertussis isolates collected that are lacking expression of pertactin. These isolates seem to be as virulent as those expressing all virulence factors according to animal and cellular models of infection. Whereas wP vaccine-induced immunity led to a monomorphic population of B. pertussis, aP vaccine-induced immunity enabled the number of circulating B. pertussis and B. parapertussis isolates not expressing virulence factors to increase, sustaining our previous hypothesis.

Prevalence of Bordetella pertussis and Bordetella parapertussis infections in Tunisian hospitalized infants: results of a 4-year prospective study

The prevalence of pertussis in Tunisia remains undetermined essentially because of the unavailability of a basic laboratory diagnostic service. Specific diagnostic tools were applied for the first time in a Tunisian prospective study in order to get a first estimation of the prevalence of Bordetella pertussis/parapertussis infections and to evaluate their use to determine the epidemiologic characteristics of these infections in Tunisian infants. Between 2007 and 2011, a total of 626 samples from 599 infants aged <1 year with and without pertussoid cough were investigated for the presence of B. pertussis/parapertussis using culture and real-time polymerase chain reaction (PCR). The real-time PCR (RT-PCR) targets include IS481 commonly found in B. pertussis, B. bronchiseptica, and B. holmesii; IS1001 specific of B. parapertussis, in combination with the pertussis toxin promoter region gene (ptx) of B. pertussis; and the recA gene specific of B. holmesii. When possible, patients' household contacts provided nasopharyngeal aspirates (NPAs) for RT-PCR detection of B. pertussis/parapertussis or single-serum samples for anti-PT IgG quantification. All except 1 NPAs were negative by conventional culture, whereas PCR gave positive signals for 126 specimens (21%): B. pertussis, B. parapertussis, and Bordetella spp. were detected in 82%, 6%, and 4% of the samples, respectively. The simultaneous presence of B. pertussis and B. parapertussis was noted in 8% of the cases. Pertussis was reported throughout the year with a peak during the summer of the year 2009. The prevalence of Bordetella infection was 20% between 2007 and 2011. Most of these cases corresponded to patients younger than 6 months who received <3 doses of pertussis vaccine. Among the household contacts enrolled in the study, mothers seemed to be the likely source of infection. This study showed that pertussis is still prevalent in Tunisia and that the disease remains a public health problem affecting not only infants but also adults. Given this situation, sensitive and specific laboratory tests are needed to improve the accuracy of pertussis diagnosis.

[Pertussis vaccination for parents: proposal and evaluation of two professional practices in a maternity hospital]

BACKGROUND

Despite good rates of immunization among children, an apparent increase in the incidence of pertussis disease in infants in France has been observed, mainly because of low vaccination coverage among adults. Guidelines drawn up in 2004 recommend a vaccination strategy called cocooning for parents, but those guidelines are rarely followed by the medical community. Raising the vaccination rate among parents to 65% and the extension of pertussis vaccine booster for people between 26 and 28 years old could help control the disease.

OBJECTIVE AND METHODS

In a primary healthcare setting in 2009, we studied 2 groups of 188 and 190 parents of newborns in a maternity unit. We proposed 2 strategies: information and vaccine prescription for both parents (if eligible) at the time of discharge from the maternity unit (group 1) or vaccination proposed to both parents during hospitalization in the maternity unit (group 2). After 6 weeks, the vaccination rates of both groups were compared.

RESULTS

Analysis shows that parents had insufficient knowledge of the disease. Parents were often unaware of their vaccination status. Hence, objective data concerning the vaccination status was quickly available for only 42% of the population, making determination of eligibility unreliable. Only 8% of the parents were up to date for pertussis vaccination in the last 10 years, whereas 90% of the parents had the opportunity for vaccination and 37% of them had been eligible before the pregnancy. At the end of the study, 53% of the parents in group 1 were vaccinated, showing the positive impact of the medical encounter and vaccine prescription. During the study, 40% of the parents in group 2 who were proposed immediate vaccination in the maternity unit accepted it. This increased to 43% of group 2 parents being immunized by the time they had left the maternity unit. Proposing the vaccination at the maternity hospital was the more effective of the 2 strategies (P=0.03): at the end of the study, the objective was nearly reached with 64% of the parents being vaccinated.

CONCLUSIONS

The promotion of parental vaccination by the pediatrician in the maternity ward is simple and effective. Medical encounters resulting from prescriptions made during hospitalization could raise awareness in general practitioners and enable them to identify eligible adults for pertussis vaccination and vaccinate themselves. There is a need to discuss the complementarity and interactions between perinatal teams and general practitioners within the community healthcare network.

Immunogenicity and safety study of a new DTaP-IPV-Hep B-PRP-T combined vaccine compared to a licensed DTaP-IPV-Hep B//PRP-T comparator, both concomitantly administered with a 7-valent pneumococcal conjugate vaccine at 2, 4, and 6 months of age in Thai infants

OBJECTIVE

To assess a new, fully-liquid, hexavalent DTaP-IPV-Hep B-PRP-T vaccine (diphtheria toxoid (D), tetanus toxoid (T), acellular pertussis (aP), inactivated poliovirus (IPV), hepatitis B (Hep B), and Haemophilus influenzae type b polysaccharide conjugated to tetanus protein (PRP-T) antigens) compared to a licensed DTaP-IPV-Hep B//PRP-T vaccine following primary series co-administration with a 7-valent pneumococcal conjugate vaccine (PCV7).

METHODS

This was a randomized, phase III, observer-blind study in Thai infants (N=412), who received DTaP-IPV-Hep B-PRP-T or DTaP-IPV-Hep B//PRP-T at 2, 4, and 6 months of age, co-administered with PCV7. All received Hep B at birth. Non-inferiority for Hep B ≥ 10 mIU/ml and PRP ≥0.15μg/ml was analyzed (DTaP-IPV-Hep B-PRP-T relative to DTaP-IPV-Hep B//PRP-T) at 1 month post-primary. Seroprotection/seroconversion and geometric mean titers (GMTs) were analyzed descriptively for all hexavalent components. Safety was evaluated from parental reports.

RESULTS

Anti-Hep B and anti-PRP antibody seroprotection rates were high for DTaP-IPV-Hep B-PRP-T (n=189) and DTaP-IPV-Hep B//PRP-T (n=190), and non-inferiority was demonstrated. Anti-D and anti-T ≥ 0.01 IU/ml, anti-polio types 1, 2, and 3 ≥ 8 (1/dil), and anti-PT and anti-FHA seroconversion were high and similar in each group. For DTaP-IPV-Hep B-PRP-T and DTaP-IPV-Hep B//PRP-T, anti-Hep B ≥ 100 mIU/ml was 98.4% and 99.5% (GMTs 2477 and 2442 mIU/ml), respectively; anti-PRP ≥ 1.0 μg/ml was 85.2% and 71.1% (GMTs 5.07 and 2.41 μg/ml), respectively. Safety profiles were comparable. There were no vaccine-related serious adverse events.

CONCLUSIONS

Following co-administration with PCV7 the investigational DTaP-IPV-Hep B-PRP-T vaccine was safe and immunogenic. Non-inferiority to DTaP-IPV-Hep B//PRP-T was shown for Hep B and PRP.

Prospective pertussis surveillance in Switzerland, 1991-2006

Pertussis has been monitored in Switzerland since 1991 by the nationwide Swiss Sentinel Surveillance Network (SSSN), consisting of approximately 200 general practitioners, internists and pediatricians representing about 3% of the total primary care physicians of these specialities. SSSN members report patients with cough ≥ 14 days plus either an epidemiological link or characteristic symptoms (paroxysms, whoop, post-tussive vomiting) on a weekly basis to the Federal Office of Public Health. Confirmatory PCR from nasopharyngeal specimens is offered for free. A total of 4992 cases have been reported until 2006. Yearly incidence has dropped from 70 cases per 100,000 inhabitants in 1992 to 40 in 2006, with a single epidemic in 1994-1995 with 280-370 cases/100,000. On average 80% of reported cases were tested by PCR, 24% of these were confirmed as Bordetella pertussis infections. For 2.6% of patients complications were reported, most commonly pneumonia, asthma bronchiale, otitis media, bronchitis and rib fractures. On average, 1.5% of patients were hospitalized. Disease in vaccinated patients was mitigated with less frequent complications (unvaccinated: 5.1%; 3 doses: 3.0%; ≥ 4 doses: 1.7%), hospitalizations (unvaccinated: 3.6%; ≥ 1 dose: 1.1%) and various clinical symptoms compared to unvaccinated patients. Comparing the periods 1991-1996, 1997-2001 and 2002-2006, a shift of pertussis from age group 1-9 years to 10-19 and ≥ 40 years was observed among patients cared for by general practitioners and internists. The benefits of further booster doses in adolescents and/or adults need to be considered.

Pertussis prevention and diagnosis practices for adolescents and adults among a national sample of French general practitioners

Authors report a cross-observational study conducted to determine the awareness and adherence of general practioners (GPs) to pertussis vaccine guidelines; to identify the barriers encountered by GPs to adhering to these guidelines; and to describe diagnosis and case management approaches for adolescent and adult pertussis in France. This study, conducted independently of any pharmaceutical companies, concludes that greater awareness of the public health morbidity and mortality of pertussis, intensive immunization adherence for all those in contact with infants, and adherence to routine immunization schedules are necessary to reduce the burden of disease due to Bordetella pertussis. The barriers encountered (the most important were the incomprehension of patients who are not informed about the circulation of pertussis in the adult population and the fact that pertussis is not commercialized as a monovalent vaccine) should be examined further as they do not seem to be related to a lack of GP knowledge. Public information campaigns are needed. The results emphasize the need of policy development for management of pertussis in France.

First report and detailed characterization of B. pertussis isolates not expressing Pertussis Toxin or Pertactin

Bordetella pertussis isolates not expressing Pertussis Toxin (PT) or Pertactin (PRN) have been collected, for the first time in 2007, in France, a highly vaccinated country with acellular vaccines. Non-expression was due to deletion of the entire ptx locus, to IS481 insertion in the prn gene or deletion of a part of this gene. Genome sequencing does not indicate any regions of differences when compared to other circulating isolates. It nevertheless shows some sequence differences and an increased number of repeated sequences. The infant infected by the isolate not expressing pertussis toxin, did not present hyperlymphocytosis. All isolates were found less pathogen in animal or cellular models; their circulation raises the problem of clinical and biological diagnoses.

[Pertussis surveillance in French military forces in 2007]

OBJECTIVES

Pertussis surveillance in the French general population was stopped in 1986. Pertussis was added to the list of illnesses surveyed by the military epidemiological surveillance network because of outbreaks having occurred among French servicepersons and in military high schools. This study had for aim to report the results of the first year of surveillance.

DESIGN

Pertussis declaration criteria were those recommended in 2006 by the French council for public hygiene. The data concerning active military servicepersons was collected by physicians of all military medical units. An anonymous declaration form was used for data collection.

RESULTS

In 2007, 66 cases of pertussis were reported in the military forces, 10 of which were excluded after a negative biological test. The classification of the 56 included cases was: 46% biologically confirmed cases, 20% clinically confirmed cases, 14% suspected cases, and 6% epidemiologically confirmed cases. The incidence density rate was 16.3 cases for 100,000 servicepersons-years. Age under 20 was associated with a 4.6 fold higher risk to develop pertussis.

CONCLUSIONS

The high incidence rate observed in individuals under 20 years of age could reflect a shift of pertussis reservoir to young adults, as observed in industrialized countries after generalization of vaccination programs. However, several years of surveillance will be needed to confirm this hypothesis. Meanwhile, the military epidemiological network could constitute an important surveillance marker of pertussis among adults in France.

[Awareness and adherence to Pertussis vaccination guidelines by occupational medicine physicians in Paris healthcare institution]

OBJECTIVE

A questionnaire was used on 44 public and private hospital physicians in Paris to evaluate their knowledge of and adherence to Vaccination Guidelines, three years after their introduction.

RESULTS

Eighty per cent of the physicians answered and 92.5% were aware of the vaccination guidelines but only 2 out of 4 respected the targeted vaccination in young adults even when the vaccine was available. A policy of pertussis vaccination was applied only in 12 institutions, but even in these, the rate of vaccinated healthcare workers remained low or was not documented.

CONCLUSION

Pertussis is a potential risk to newborns not or partially vaccinated in France. Even if the vaccine is available, adherence to pertussis vaccination guidelines must be improved. Efforts should be made to better publicize and apply pertussis vaccination guidelines.

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.

International Bordetella pertussis assay standardization and harmonization meeting report. Centers for Disease Control and Prevention, Atlanta, Georgia, United States, 19-20 July 2007

An international meeting on Bordetella pertussis assay standardization and harmonization was held at the Centers for Disease Control and Prevention (CDC), Atlanta, GA, 19–20 July 2007. The goal of the meeting was to harmonize the immunoassays used for pertussis diagnostics and vaccine evaluation, as agreed upon by academic and government researchers, regulatory authorities, vaccine manufacturers, and the World Health Organization (WHO).

The primary objectives were (1) to provide epidemiologic, laboratory, and statistical background for support of global harmonization; (2) to overview the current status of global epidemiology, pathogenesis and immunology of pertussis; (3) to develop a consensus opinion on existing gaps in understanding standardization of pertussis assays used for serodiagnosis and vaccine evaluation; and (4) to search for a multicenter process for addressing these priority gaps. Presentations and discussions by content experts addressed these objectives. A prioritized list of action items to improve standardization and harmonization of pertussis assays was identified during a group discussion at the end of the meeting. The major items included: (1) to identify a group that will organize, prepare, maintain, and distribute proficiency panels and key reagents such as reference and control sera; (2) to encourage the development and identification of one or more reference laboratories that can serve as an anchor and resource for other laboratories; (3) to define a performance-based assay method that can serve as a reference point for evaluating laboratory differences; (4) to develop guidance on quality of other reagents, e.g., pertussis toxin and other antigens, and methods to demonstrate their suitability; (5) to establish an international working group to harmonize the criteria to evaluate the results obtained on reference and proficiency panel sera; (6) to create an inventory to determine the amount of appropriate and well-characterized sera that are available globally to be used as bridging reagents for vaccine licensure; and (7) to seek specific guidance from regulatory authorities regarding the expectations and requirements for the licensure of new multicomponent pertussis vaccines.