Overview of pertussis: focus on epidemiology, sources of infection, and long term protection after infant vaccination

A decennial booster dose of reduced antigen content diphtheria, tetanus, acellular pertussis vaccine (Boostrix™) is immunogenic and well tolerated in adults

Reduced-antigen-content diphtheria-tetanus-acellular-pertussis (dTpa) vaccines are predominantly recommended for once-in-a-lifetime use. A second dTpa (Boostrix™, GlaxoSmithKline Biologicals) administration in 164 adults previously vaccinated with dTpa 10 years previously was evaluated. Before the decennial booster, 89.4% and 94.8% subjects were seroprotected (antibodies ≥0.1 IU/mL) for diphtheria and tetanus, respectively. One-month post-booster, all subjects were seroprotected/seropositive against all vaccine antigens. Robust GMC increases indicated a booster response similar to the first booster. The decennial booster was well tolerated without serious adverse events, consistent with product experience. This study supports replacing traditional Td boosters with dTpa, and use of Boostrix™ as a decennial booster. This study is registered at www.clinicaltrials.com NCT00548171.

Pertussis-the case for universal vaccination

PURPOSE

Does the literature support universal vaccination of adolescents and adults, reducing disease incidence in infants and young children?

DESIGN & METHODS

An extensive literature review and a meta-analysis of four case-control studies, evaluating effects of missed or late vaccine doses, was conducted.

RESULTS

The literature confirms (a) increasing pertussis rates; (b) adults and adolescents are the primary carriers; (c) vaccine effectiveness wanes over time; and (d) pertussis persists despite disease control efforts.

PRACTICE IMPLICATIONS

Missed or late doses mean an increase in likelihood of contracting pertussis, supporting full vaccination for children and boosters for adolescents/adults.

Long-term immunity against pertussis induced by a single nasal administration of live attenuated B. pertussis BPZE1

Duration of vaccine-induced immunity plays a key role in the epidemiology and in the pattern of transmission of a vaccine-preventable disease. In the case of whooping cough, its re-emergence has been attributed, at least partly, to the waning of immunity conferred by current pertussis vaccines. We have recently developed a highly attenuated live vaccine, named BPZE1, which has been shown to be safe and to induce strong protective immunity against Bordetella pertussis infection in mice. In this study, we evaluated the long-term immunogenicity and protective efficacy induced by a single intranasal dose of BPZE1. Up to 1 year after immunization, BPZE1 showed significantly higher efficacy to protect adult and infant mice against B. pertussis infection than two administrations of an acellular pertussis vaccine (aPV). B. pertussis-specific antibodies were induced by live BPZE1 and by aPV, with increasing amounts during the first 6 months post-immunization before a progressive decline. Cell-mediated immunity was also measured 1 year after immunization and showed the presence of memory T cells in the spleen of BPZE1-immunized mice. Both cell-mediated and humoral immune responses were involved in the long-lasting protection induced by BPZE1, as demonstrated by adoptive transfer experiments to SCID mice. These data highlight the potential of the live attenuated BPZE1 candidate vaccine as part of a strategy to solve the problem of waning protective immunity against B. pertussis observed with the current aPV vaccines.

Post-marketing safety evaluation of a tetanus toxoid, reduced diphtheria toxoid and 3-component acellular pertussis vaccine administered to a cohort of adolescents in a United States health maintenance organization

BACKGROUND

Prelicensure clinical studies may not include sufficient numbers of subjects to assess the potential for rare postvaccination adverse events. The aim of this postlicensure study (NCT00297856) was to evaluate uncommon outcomes following vaccination with a tetanus, reduced-antigen-content diphtheria, and acellular pertussis vaccine (Tdap, Boostrix GlaxoSmithKline) in a large adolescent cohort.

METHODS

We monitored safety outcomes among 13,427 10 to 18-year-old adolescents enrolled in the Northern California Kaiser Permanente Health Care Plan who received Tdap vaccination as part of their normal health care. Subjects were evaluated using self-control analysis comparing days 0 to 29 to days 30 to 59 postvaccination for neurologic events, hematologic events and allergic reactions. We evaluated new onset chronic illnesses within 6 months of Tdap vaccination by comparing with historical Td controls matched for age at vaccination, season, sex, and geographic area. We also compared the incidence of events of interest between the Tdap and historical cohorts as exploratory analyses.

RESULTS

No increased risk for medically attended neurologic (odds ratio [OR], 0.962; 95% confidence interval [CI], 0.533-1.733) or allergic reactions (OR, 1.091; 95% CI, 0.441-2.729) was observed following Tdap vaccination when comparing the first 30 postvaccination days to the second 30 postvaccination days. There was one hematologic event within 30 days of Tdap, compared with 0 events within days 30 to 59 (P = 1.0). When compared with matched historical Td recipients, no increase in new onset chronic illnesses (OR, 0.634; 95% CI, 0.475-0.840) was seen after Tdap. No deaths occurred in the Tdap cohort during the study.

CONCLUSIONS

This study provides no evidence for an increased risk for neurologic, hematologic, allergic events, or new onset of chronic illnesses among adolescents vaccinated with Tdap.

Update on pertussis and pertussis immunization

Pertussis is a highly contagious respiratory tract disease caused by Bordetella pertussis infection. The clinical manifestation of this infection can be severe enough to cause death. Although pertussis has been supposed to be a vaccine-preventable disease ever since the widespread vaccination of children against pertussis was started, since the 1990s, cases of pertussis and related fatalities are on the rise, especially in countries with high vaccination coverage. In Korea, there have been no deaths due to pertussis since 1990, and the vaccination rate continues to be approximately 94%. However, the number of pertussis cases reported to the Korea Center for Disease Control and Prevention has tended to increase in the 2000s, and in 2009, there was an obvious increase in the number of pertussis cases reported. This review aims to present the latest information about the pathogenesis, diagnosis, treatment, and prevention of pertussis.

T- and B-cell-mediated protection induced by novel, live attenuated pertussis vaccine in mice. Cross protection against parapertussis

Background

Despite the extensive use of efficacious vaccines, pertussis still ranks among the major causes of childhood mortality worldwide. Two types of pertussis vaccines are currently available, whole-cell, and the more recent acellular vaccines. Because of reduced reactogenicity and comparable efficacy acellular vaccines progressively replace whole-cell vaccines. However, both types require repeated administrations for optimal efficacy. We have recently developed a live attenuated vaccine candidate, named BPZE1, able to protect infant mice after a single nasal administration.

Methodology/Principal Findings

We determined the protective mechanism of BPZE1-mediated immunity by using passive transfer of T cells and antibodies from BPZE1-immunized mice to SCID mice. Clearance of Bordetella pertussis from the lungs was mediated by both BPZE1-induced antibodies and CD4⁺, but not by CD8⁺ T cells. The protective CD4⁺ T cells comprised IFN-γ-producing and IL-17-producing subsets, indicating that BPZE1 induces both Th1 and Th17 CD4⁺ T cells. In addition, and in contrast to acellular pertussis vaccines, BPZE1 also cross-protected against Bordetella parapertussis infection, but in this case only the transfer of CD4⁺ T cells conferred protection. Serum from BPZE1-immunized mice was not able to kill B. parapertussis and did not protect SCID mice against B. parapertussis infection.

Conclusions/Significance

The novel live attenuated pertussis vaccine BPZE1 protects in a pre-clinical mouse model against B. pertussis challenge by both BPZE1-induced antibodies and CD4⁺ T cell responses. It also protects against B. parapertussis infection. However, in this case protection is only T cell mediated.

Pertussis antibodies in postpartum women and their newborns

OBJECTIVE

To (1) determine the proportion of mothers and infants who had levels of IgG antibody to pertussis antigens predicted to be potentially protective at delivery; (2) evaluate the efficiency of maternal-infant antibody transport; (3) extrapolate infant antibody titers at 6 weeks; and (4) identify maternal factors associated with potentially protective infant antibodies.

STUDY DESIGN

Sera from mother-infant pairs from February 2006 through to April 2007 were tested for antibody to pertussis antigens by standardized ELISA (enzyme-linked immunosorbent assay). Potentially protective antibody levels were defined as >5 ELISA units (EU) for pertussis toxin (PT), and >10 EU for fimbriae (FIM) and pertactin (PRN). Serological evidence of previous maternal infection was defined from antibody to four antigens by k-means cluster analysis.

RESULT

In total, 21% (17/81) of mothers and 26% (21/81) of infants had potentially protective antibody levels at delivery. Mean infant-maternal antibody ratios for PT, FIM and PRN were 1.26, 1.36 and 1.31, respectively. At 6 weeks, 11% (9/81) of infants were predicted to have potentially protective antibody levels. Using cluster analysis, 9% (7/81) of mothers had evidence of previous pertussis infection. Infants born to these mothers were predicted to be more likely to have potentially protective antibodies at 6 weeks (43%) than those born to mothers without previous infection (8%) (P=0.03).

CONCLUSION

Approximately 75% of infants were born with pertussis antibody levels lower than the modest levels associated with potential protection. Despite effective antibody transfer, nearly 90% of infants were predicted to have little antibody by 6 weeks. Maternal immunization before or during pregnancy might simulate previous pertussis infection and help protect infants through the first months of life.

Bordetella pertussis strains with increased toxin production associated with pertussis resurgence

A more virulent strain of the disease is emerging.

Before childhood vaccination was introduced in the 1940s, pertussis was a major cause of infant death worldwide. Widespread vaccination of children succeeded in reducing illness and death. In the 1990s, a resurgence of pertussis was observed in a number of countries with highly vaccinated populations, and pertussis has become the most prevalent vaccine-preventable disease in industrialized countries. We present evidence that in the Netherlands the dramatic increase in pertussis is temporally associated with the emergence of Bordetella pertussis strains carrying a novel allele for the pertussis toxin promoter, which confers increased pertussis toxin (Ptx) production. Epidemiologic data suggest that these strains are more virulent in humans. We discuss changes in the ecology of B. pertussis that may have driven this adaptation. Our results underline the importance of Ptx in transmission, suggest that vaccination may select for increased virulence, and indicate ways to control pertussis more effectively.

Levels of childhood vaccination coverage and the impact of maternal HIV status on child vaccination status in rural KwaZulu-Natal, South Africa*

OBJECTIVES

To analyse coverage of childhood vaccinations in a rural South African population and investigate whether maternal HIV status is associated with children's vaccination status.

METHODS

2 431 children with complete information, 12-23 months of age at some point during the period January 2005 through December 2006 and resident in the Africa Centre Demographic Surveillance Area at the time of their birth were investigated. We examined the relationship between maternal HIV status and child vaccination status for five vaccinations [Bacillus Calmette-Guérin (BCG), diphtheria-tetanus-pertussis (DTP3), poliomyelitis (polio3), hepatitis B (HepB3), and measles] in multiple logistic regressions, controlling for household wealth, maternal age, maternal education and distances to roads, fixed and mobile clinics.

RESULTS

Coverage of the five vaccinations ranged from 89.3% (95% CI 81.7-93.9) for BCG to 77.3% (67.1-83.6) for measles. Multivariably, maternal HIV-positive status was significantly associated with lower adjusted odds ratios (AOR) of child vaccination for all vaccines [(AOR) 0.60-0.74, all P < or = 0.036] except measles (0.75, P = 0.073), distance to mobile clinic was negatively associated with vaccination status (all P < or = 0.029), household wealth was positively (all P < or = 0.013) and distance to nearest road negatively (all P < or = 0.004) associated with vaccination status.

CONCLUSION

Positive maternal HIV status independently reduces children's probability to receive child vaccinations, which likely contributes to the morbidity and mortality differential between children of HIV-positive and HIV-negative mothers. As a means of increasing vaccination coverage, policy makers should consider increasing the number of mobile clinics in this and similar communities in rural Africa.

Development and analytical validation of an immunoassay for quantifying serum anti-pertussis toxin antibodies resulting from Bordetella pertussis infection

Adequately sensitive and specific methods to diagnose pertussis in adolescents and adults are not widely available. Currently, no Food and Drug Administration-approved diagnostic assays are available for the serodiagnosis of Bordetella pertussis. Since concentrations of B. pertussis-specific antibodies tend to be high during the later phases of disease, a simple, rapid, easily transferable serodiagnostic test was developed. This article describes test development, initial evaluation of a prototype kit enzyme-linked immunosorbent assay (ELISA) in an interlaboratory collaborative study, and analytical validation. The data presented here demonstrate that the kit met all prespecified criteria for precision, linearity, and accuracy for samples with anti-pertussis toxin (PT) immunoglobulin G (IgG) antibody concentrations in the range of 50 to 150 ELISA units (EU)/ml, the range believed to be most relevant for serodiagnosis. The assay met the precision and linearity criteria for a wider range, namely, from 50 to 200 EU/ml; however, the accuracy criterion was not met at 200 EU/ml. When the newly adopted World Health Organization International Standard for pertussis antiserum (human) reference reagent was used to evaluate accuracy, the accuracy criteria were met from 50 to 200 international units/ml. In conclusion, the IgG anti-PT ELISA met all assay validation parameters within the range considered most relevant for serodiagnosis. This ELISA was developed and analytically validated as a user-friendly kit that can be used in both qualitative and quantitative formats. The technology for producing the kit is transferable to public health laboratories.

Epidemiology of pertussis and Haemophilus influenzae type b disease in Canada with exclusive use of a diphtheria-tetanus-acellular pertussis-inactivated poliovirus-Haemophilus influenzae type b pediatric combination vaccine and an adolescent-adult tetanus-diphtheria-acellular pertussis vaccine: implications for disease prevention in the United States

BACKGROUND

During the decade 1998-2007, a combination DTaP(5)-IPV/Hib vaccine was used exclusively in Canada to immunize infants and young children against diphtheria, tetanus, pertussis, polio, and invasive Haemophilus influenzae type b (Hib) disease.

METHODS

Medline was used to search for publications during 1996-2008 related to the epidemiology and vaccine prevention of pertussis and invasive Hib disease in Canada. Related abstracts and presentations were reviewed, when available, and epidemiologic data since 1985 were obtained from the Public Health Agency of Canada public Web site.

RESULTS

Reports of pertussis have declined substantially in preschool and school-aged children during the past decade, and cyclical peaks in disease incidence have been blunted or eliminated. In provinces and territories where Tdap(5) vaccine has been administered to 14- to 16-year-olds, marked reductions of pertussis have been documented in adolescents as well as younger age groups, possibly due to herd immunity. Incidence rates of invasive Hib disease among Canadian children <5 years declined markedly after introduction of Hib conjugate vaccines, and the disease has remained under control with exclusive use of DTaP(5)-IPV/Hib vaccine. Most cases of invasive Hib disease occur among unimmunized or only partially vaccinated children. The reduction of Hib case reports has been documented throughout Canada, including among Aboriginal children who are at high risk for this disease.

CONCLUSIONS

The Canadian experience with DTaP(5)-IPV/Hib and Tdap(5) vaccines is relevant to the United States because immunization schedules, vaccination coverage rates, and epidemiologic patterns of pertussis and Hib diseases are similar in the 2 countries, and because both vaccines are licensed for use in the United States.

Epidemiological characteristics of pertussis in Estonia, Lithuania, Romania, the Czech Republic, Poland and Turkey-1945 to 2005

Pertussis epidemiology was examined in selected Central and Eastern European countries andTurkey (CEEs) from 1945 to 2005. Epidemiology and immunisation coverage data were collected fromNational Health Departments and Epidemiology Institutes. Pertussis diagnosis was made by the World Health Organization (WHO) clinical criteria, laboratory confirmation and/or epidemiological link, except for Romania (WHO clinical case definition used). In the pre-vaccine era, pertussis incidence (except Turkey) exceeded 200/100,000 (range180-651/100,000), with 60-70% of cases occurring in pre-school children. Until 2007, a second-year booster was givenin Estonia, Lithuania and Turkey, and an additional pre-school booster elsewhere. During 1995-2005, immunisation coverage by the age of 2 years exceeded 80% (range 80-98%) and, excluding Estonia, pertussis incidence was <3/100,000. Age-specific incidence rates rose in 5-14 year olds in Poland, Estonia and the Czech Republic. Incidence rates in children <1 year of age remained unchanged. There were two age distribution patterns. In the Czech Republic and Estonia, 16% of cases occurred in pre-school children and 17% and 22% in children >15 years of age, respectively; in Romania, Turkey and Lithuania, 51%, 71% and 73%, respectively, occurred in pre-school children and <7% in children aged >15 years.Pertussis infection persists, despite high immunisation coverage. Compared with the pre-vaccine era, the age distribution changed differentially in CEEs, with an apparent shift towards older children.

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.

Immunogenicity and safety of a tetanus toxoid, reduced diphtheria toxoid and three-component acellular pertussis vaccine in adults 19-64 years of age

PURPOSE

This study was conducted to assess the immunogenicity and safety of a tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine containing three pertussis antigens (Boostrix, Tdap3v), currently licensed in the US for use in adolescents 10-18 years of age, in adults 19-64 years of age.

METHODS

2284 healthy adults, aged 19-64 years, were randomized to receive a single dose of Tdap vaccine, either Tdap3v or a five-pertussis component Tdap vaccine (Adacel, Tdap5v) licensed for adult use in the US. Blood samples were taken before and 1 month after vaccination. Reactogenicity was assessed for 15 days after vaccination.

RESULTS

Tdap3v was comparable to Tdap5v in eliciting seroprotective levels of antibodies to diphtheria and tetanus toxoids, with >98% of subjects having post-vaccination seroprotective antibody levels (> or =0.1 IU/mL) against diphtheria or tetanus toxoids. The pertussis components of Tdap3v were shown to be immunogenic in adults, with booster responses to pertussis toxoid (PT), filamentous hemagglutinin (FHA), and pertactin (PRN) observed in 77.2%, 96.9%, and 93.2%, respectively, of Tdap3v recipients, and in 47.1%, 94.0%, and 91.7%, respectively, of Tdap5v recipients. Anti-pertussis antibody GMCs in Tdap3v recipients exceeded those observed in infants following primary DTaP vaccination, in whom efficacy against pertussis disease was subsequently demonstrated. Injection site reactions (pain, redness, and swelling) and fever > or =37.5 degrees C (99.5 degrees F) were reported significantly more often (p<0.05) by Tdap5v recipients than by Tdap3v recipients. Fatigue preventing normal daily activities was reported by a small but significantly greater percentage of Tdap3v recipients (2.5%) than Tdap5v recipients (1.2%, p<0.05).

CONCLUSION

In adult recipients, Tdap3v was comparable to an approved Tdap vaccine in providing seroprotection against diphtheria and tetanus, and produced immune responses to pertussis antigens consistent with protection against disease. The overall safety profile of Tdap3v was generally comparable to that of Tdap5v [NCT #106316].

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.

Pertussis: review of epidemiology, diagnosis, management and prevention

Bordetella pertussis--the cause of pertussis or whooping cough--is an exclusively human pathogen. Disease elimination by vaccination should, therefore, be possible, but has proved elusive. Many industrialised countries with long established immunisation programs are currently seeing a resurgence of pertussis, despite universal vaccination with high uptake, with the highest burden in the least immunised age groups (infants under 6 months of age and persons over 10 years old). However, low recognition and reporting and insensitive diagnostic tests mean that the true burden of pertussis is still underestimated. Recently, efforts to improve diagnostic yield include the expanded use of polymerase chain reaction and serological tests but both have significant limitations. The range of antibiotics available for treatment and prophylaxis has expanded to include the newer macrolides, azithromycin and clarithromycin, and a range of universal and targeted vaccination strategies have been implemented or proposed. This paper reviews the current epidemiology of pertussis in developed countries, including modes of clinical presentation, diagnosis, management and potential vaccination strategies.

[PCR testing for Bordetella pertussis in household contacts as a diagnostic tool for atypical whooping cough in unvaccinated young infants]

INTRODUCTION

False-negative findings of polymerase chain reaction (PCR) for genuine pertussis as well as the numerous atypical forms of whooping cough make it difficult to diagnose this disease in young babies.

METHODS

For two years, real-time PCR was performed to test for Bordetella pertussis in 86 infants younger than 6 months hospitalized for apnea or paroxysmal and/or vomiting cough and in 205 of their household contacts, whether or not they coughed.

RESULTS

Group 1 included 30 infants for whom PCR detected B. pertussis (25 of whom were also RSV+). PCR was also positive for at least one household contact in 25/30 families. This group included 16 babies with apnea and 12 who developed a whooping cough during follow-up. Group 2 comprised 12 infants whose PCR was negative while at least one household contact had positive results. Five of these infants had severe apnea and 6 developed a whooping cough. Group 3 included 44 infants (28 RSV +) for whom PCR was negative in the index case and in the household contacts: none developed a whooping cough during follow-up. Only 3 of the 54 positive household contacts had a paroxysmal cough or a typical whooping cough and 12 had no cough at all.

CONCLUSION

Positive PCR in a household contact, symptomatic or not, is helpful for the diagnosis of atypical whooping cough in young infants.

Estimating the role of casual contact from the community in transmission of Bordetella pertussis to young infants

The proportion of infant pertussis cases due to transmission from casual contact in the community has not been estimated since before the introduction of pertussis vaccines in the 1950s. This study aimed to estimate the proportion of pertussis transmission due to casual contact using demographic and clinical data from a study of 95 infant pertussis cases and their close contacts enrolled at 14 hospitals in France, Germany, Canada, and the U.S. between February 2003 and September 2004. A complete case analysis was conducted as well as multiple imputation (MI) to account for missing data for participants and close contacts who did not participate. By considering all possible close contacts, the MI analysis estimated 66% of source cases were close contacts, implying the minimum attributable proportion of infant cases due to transmission from casual contact with community members was 34% (95% CI = 24%, 44%). Estimates from the complete case analysis were comparable but less precise. Results were sensitive to changes in the operational definition of a source case, which broadened the range of MI point estimates of transmission from casual community contact to 20%–47%. We conclude that casual contact appears to be responsible for a substantial proportion of pertussis transmission to young infants.

Medical subject headings (MeSH): multiple imputation, pertussis, transmission, casual contact, sensitivity analysis, missing data, community.

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

Persistence of antibodies following a single dose of Tdap vaccine (tetanus, diphtheria, and five-component acellular pertussis vaccine for use in individuals past childhood) was evaluated in a follow-up of adolescents (N=324) and adults (N=644) who had received Tdap in earlier clinical trials. Outcome measures were seroprotection (tetanus and diphtheria) or seropositivity (pertussis) and geometric mean titers. Humoral immune responses to all antigens were robust 1 month after initial immunization; antibodies exceeded pre-immunization levels 1, 3, and 5 years later. These data will contribute to selecting the optimal interval for booster doses of Tdap.

Children with pertussis inform the investigation of other pertussis cases among contacts

Background

The number of reported pertussis has increased in the last two decades. However, many cases of pertussis may be underreported or not diagnosed. The World Health Organization estimates that pertussis causes 200.000 – 400.000 deaths each year, most deaths are in infants and in developing countries. Infants with pertussis can indicate an undetected source cases in the community.

Methods

At a University Hospital in Brazil individuals that had frequent contacts with a child with confirmed pertussis (the index case) and had recent history of cough were enrolled into the study. Nasopharyngeal swabs were collected from every contact that had cough within the last 21 days. Cases confirmation followed the guidelines of the Center for Disease Control and Prevention – Atlanta, U.S.A.

Results

Pertussis diagnosis was confirmed in 51 children, (considered the index cases). Among the index cases, 72.5% (37/51) were under 6 months of age; culture for Bordetella pertussis was positive in 78.4% (40/51). Pertussis was confirmed in 39% (107/276) of the contacts of 51 index cases. Among these contacts identified as a pertussis case, 40.2% (43/107) were between 6 months and 11¹/₂ years of age and 59.8% (64/107) were older than 11¹/₂ years of age. Pertussis was confirmed by culture in 11.2% (12/107) of them and by epidemiologic linkage in 88.8% (95/107). Each index case allowed identifying two new cases of pertussis.

Conclusion

Public health authorities should consider implementing early recognition of pertussis index cases and searching for pertussis cases among the contacts. Treatment of the cases and prophylaxis of the contacts is fundamental to control outbreaks in the community.

Vaccins et professions exposées

The use of safe and efficacious vaccines in occupational settings to protect workers from diseases to which they may be exposed is obvious and has been included in the employment law. Healthcare workers are particular exposed. Immunization has two purposes : protect the worker from contracting a disease, but also prevent him from disseminating the disease to weakened patients. It is important not only to take into account existing recommendations for immunization, but also to envisage their extension to teachers and staff of nurseries and primary schools. Routine vaccination against whooping cough, varicella, measles and hepatitis A is particularly warranted in these categories. Recommendations should also extend to medical students who are too often poorly protected and insufficiently warned against potential occupational exposure to pathogens and dissemination to their patients.

Epidemiological shift in the prevalence of pertussis in Taiwan: implications for pertussis vaccination

In Taiwan, routine pertussis immunization has been implemented for more than 40 years and a low incidence of pertussis was maintained until an 80-fold increase in cases occurred in 1992. The unexpected increase emphasized the significance of pertussis. This study evaluated a total of 2452 reported cases of pertussis during 1993–2004 and surveillance data on incidence, age distribution and seasonality. The highest morbidity was in infants aged <1 year, and upward trends in the incidence of pertussis were significant for infants aged <1 year and adolescents aged 10–14 years. The highest mean number of cases was observed in August and upward trends were in colder months. This study indicates that the epidemiology of pertussis may have been changed by waning immunity in Taiwan. Increased surveillance activities, especially in older age groups, and additional booster doses of acellular pertussis vaccine for children aged 6–8 years and adolescents/young adults aged 15–20 years are necessary to control and prevent pertussis.

Outbreak of pertussis on a college campus

BACKGROUND

Pertussis is increasing among adolescents and adults despite universal childhood vaccination. This investigation describes an outbreak of pertussis among undergraduate students and assesses the burden of cough illness on a college campus.

METHODS

Students presenting with prolonged cough were evaluated with culture, polymerase chain reaction (PCR), and serology. An e-mail survey was performed to determine the burden of cough illness on campus.

RESULTS

Thirty-seven undergraduates were evaluated. Their mean duration of cough was 28 days. No student had cultures positive for B. pertussis; one was PCR positive. Ten (27%) had serologic values consistent with acute pertussis infection. The e-mail survey was returned by 225/500 (45%) students. Of these, 66 (29%; 95% confidence interval [CI], 23%-36%) reported a cough of 2 weeks or longer duration during the fall semester. A conservative estimate showed that the campus-wide incidence of a cough illness meeting the Centers for Disease Control and Prevention case definition for pertussis was 13% (95% CI, 10%-16%) during the fall semester.

CONCLUSIONS

Adolescents and young adults are susceptible to pertussis infection. This study demonstrates that there was a substantial rate of pertussis infection during an outbreak on a college campus. Our findings support the routine use of the acellular pertussis vaccine in adolescents and adults.

Pertussis in young infants: apnoea and intra-familial infection

This study investigated 41 infants, aged <4 months, who were hospitalised with symptoms compatible with pertussis. Of these, 16 had Bordetella pertussis infection confirmed by real-time PCR. For four of these 16 patients, the initial sample was PCR-negative, but samples collected 5-7 days after the onset of infection were PCR-positive. PCR was also positive with samples from 15/16 families and 20/41 household contacts. Nine of the 20 positive household contacts were asymptomatic. Among the 16 infants with proven pertussis, apnoea was more frequent than in a control group for whom PCR was negative with both children and household contacts (69% vs. 28%). It was concluded that real-time PCR performed with samples from household contacts facilitates the diagnosis of infants suspected clinically of having pertussis, thereby enabling earlier treatment.

A "new age" in pertussis prevention new opportunities through adult vaccination

BACKGROUND

For the first time, pertussis vaccines for adolescents and adults (combined with tetanus and diphtheria toxoids [Tdap]) became available in the United States in 2005. Despite a fully implemented U.S. childhood pertussis vaccination program, substantial morbidity because of pertussis continues to occur. To reduce this morbidity, the Advisory Committee on Immunization Practices recommended Tdap for all adolescents and adults in place of the next tetanus-diphtheria booster. As background for the basis of these recommendations, we summarize data on the morbidity and incidence of pertussis in U.S. adults and the role of adults in transmitting pertussis to young infants.

METHODS

A MEDLINE search was performed in March 2006 for data on pertussis incidence rates and cough illness because of pertussis among U.S. adults (prospective, nonoutbreak studies were selected) and pertussis complications in adults. Data from the national passive surveillance system were also analyzed in October 2005.

RESULTS

The true adult burden is estimated at more than 600,000 cases annually in the United States. Adults with pertussis commonly cough for 2-4 months, often resulting in repeated medical visits and missed work. Complications include pneumonia, rib fractures, and cough syncope. Adults are an important source of pertussis for young infants, who have the highest risk of hospitalization and death.

CONCLUSIONS

The morbidity from pertussis in adults can be substantial, the incidence of pertussis in U.S. adults is high, and adults transmit infection to young infants. Providers now have the opportunity to reduce the burden of pertussis by vaccinating adults with Tdap.

Multitarget PCR for diagnosis of pertussis and its clinical implications

PCR has greatly facilitated pertussis diagnosis due to the speed, sensitivity, and specificity of this assay compared to other detection methods. Various single-target PCR assays are currently utilized, but none is universally considered to be the "gold standard." Our aim was to assess the use of multitarget versus single-target PCR for the diagnosis of pertussis in clinical samples. PCR assays targeting insertion sequence IS481 (IS), pertussis toxin ptxA promoter region (PT), and outer membrane porin (PO), or recA (RA) were evaluated in respiratory specimens collected from 4,442 patients with suspected pertussis. The diagnosis of pertussis was confirmed in 309 (6.96%) patients by the 3-target IS-PT-PO/RA PCR versus 247 (5.56%) by the conventional single-target IS (P=0.007). Compared to single-target IS, the three-target combination increased the proportion of positive specimens by 1.25-fold, and two-target combinations increased the proportion of positive specimens by 1.10- to 1.24-fold. In addition, nine cases of B. parapertussis infection were also confirmed by using the discriminative features of this multitarget PCR. Of the 89 culture-proven pertussis cases, 17 (19.1%) and 5 of the 16 patients (31.3%) admitted to intensive care unit would have been missed had only the single-target IS PCR been applied. Patients with mild disease (P=0.004) and shorter hospitalization (P=0.006) were less likely to have positive cultures. This consensus generating real-time PCR approach permits a sensitive detection, as well as an accurate species identification of the causative Bordetella pathogens for the timely management of patients.

Safety of reduced-antigen-content tetanus-diphtheria-acellular pertussis vaccine in adolescents as a sixth consecutive dose of acellular pertussis-containing vaccine

OBJECTIVE

The safety of a booster dose of a reduced-antigen-content tetanus-diphtheria-acellular pertussis (Tdap) vaccine was evaluated in adolescents previously vaccinated with five doses of acellular pertussis-containing vaccine.

STUDY DESIGN

Adolescents (n = 319) previously vaccinated with either 5 doses of diphtheria-tetanus-acellular pertussis (DTaP) (n = 193) or 4 doses of DTaP plus another acellular pertussis-containing vaccine received one dose each of Tdap and hepatitis A vaccine in a double-blinded, randomized, crossover trial. Rates of adverse events (AEs) after vaccination with Tdap versus hepatitis A and rates of local AEs among adolescents vaccinated with Tdap (sixth acellular pertussis-containing vaccine dose) versus rates in these same individuals after vaccination with their fifth DTaP dose were assessed.

RESULTS

After Tdap, pain (63.6%), redness (51.7%), and swelling (41.4%) were the most frequently reported AEs. Large injection site swelling (swelling > 100 mm, arm circumference increase > 50 mm or diffuse swelling interfering with daily activities) occurred in three adolescents and resolved without sequelae. After the sixth dose of acellular pertussis-containing vaccine, adolescents reported more pain and less redness and swelling compared with incidences of these AEs reported when these same individuals received their fifth DTaP dose.

CONCLUSIONS

These results suggest that Tdap is well tolerated as a sixth consecutive dose of acellular pertussis-containing vaccine.

An adolescent and adult formulation combined tetanus, diphtheria and five-component pertussis vaccine

Pertussis causes substantial morbidity among adolescents and adults, as well as other persons in contact with affected individuals. In the context of widespread childhood immunization, vaccination of adolescents and adults is a relatively new strategy for reducing the disease in all age groups. ADACEL is a tetanus-diphtheria-acellular pertussis combination vaccine (incorporating pertussis toxoid, filamentous hemagglutinin, pertactin and fimbriae type 2 and 3 antigens) formulated for use in adolescents and adults based on similar products designed for infants and children. ADACEL vaccine is approved for use in Australia, Canada, Germany and the USA, and has been demonstrated to induce robust immune responses and acceptable levels of reactogenicity in clinical trials. Surveillance data from Canada, where ADACEL vaccine has been used in adolescents and adults in conjunction with ongoing childhood vaccination for several years, indicate an enhanced overall reduction in pertussis disease.

Pertussis immunisation in adolescents and adults –Bordetella pertussisepidemiology should guide vaccination recommendations

Pertussis, or whooping cough, is an infectious disease that is caused by Bordetella pertussis, affects all age groups and is vaccine preventable. Recently, an increase in reported cases of pertussis in adolescents and adults has been noted in many countries despite high immunisation rates in children. Today pertussis outnumbers all other paediatric vaccine-preventable diseases in some countries. This observation can best be explained by an increased awareness of the disease, the availability of new diagnostic tests and, perhaps, suboptimal efficacy of some pertussis vaccines. In general, B. pertussis infections in adolescents and adults are of concern as they are the most important source of transmission of B. pertussis infections to young, unprotected infants. Many studies with diphtheria and tetanus toxoid, acellular pertussis component combination vaccines, specifically designed for use in adolescents and adults, have been performed and excellent tolerability and immunogenicity have been demonstrated. With the availability of two such products, booster doses in adolescents have been introduced in Canada, Austria, Australia, France, Germany and the US, and many other countries are considering similar expansion of their immunisation programmes at present. In addition, universal immunisation of adults (Austria, every 10 years) or targeting high risk groups (e.g., parents of newborns and other care-givers to children; Germany) have been recommended. If lifelong regular booster doses against pertussis were to be recommended and universal implementation was obtained, the authors believe that the morbidity of pertussis and its spread to infants can be dramatically reduced, and it is possible that the circulation of B. pertussis could be eliminated.

Is there a need for a new generation of vaccines against pertussis?

Current vaccines against pertussis have proved their safety and efficacy in large-scale clinical trials. Despite high vaccination coverage, pertussis is still prevalent and increasing, probably as a result of waning immunity. Addition of new antigens, such as adenylate cyclase, to current vaccines might improve some aspects of the immune response to vaccination, but are unlikely to significantly increase the duration of protection. Intranasal, oral and DNA pertussis vaccines are some way from clinical development, although one live attenuated, intranasal pertussis vaccine may soon enter Phase I trials. In the meantime, the potential of currently available safe and efficacious pertussis vaccines should be maximised. Rationalisation of pertussis boosters in childhood and introduction of widespread repeat booster vaccination in adolescents and adults would already lessen disease prevalence and morbidity among susceptible infants.

Pertussis in Infants, Children, and Adolescents: Diagnosis, Treatment, and Prevention

Pertussis, or "whooping cough," caused by the gram-negative pleomorphic bacillus Bordetella pertussis, is a highly contagious, potentially life-threatening respiratory tract illness that has re-emerged worldwide as a cause of substantial morbidity and mortality in infants, children, and adolescents, despite high vaccination rates. Increased awareness and reporting, in addition to the availability of better diagnostic tests, partially explain the recent resurgence of pertussis. However, waning immunity after childhood immunization has resulted in a growing pool of susceptible adolescents and adults who are capable of transmitting pertussis to vulnerable unvaccinated or incompletely vaccinated infants. An acellular pertussis vaccine booster for adolescents has been recommended in the United States and other industrialized countries. Active immunization and early diagnosis are crucial in the management of pertussis.