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

Comparative Evaluation of Recombinant and Acellular Pertussis Vaccines in a Murine Model

Since the 2000s, sporadic outbreaks of whooping cough have been reported in advanced countries, where the acellular pertussis vaccination rate is relatively high, and in developing countries. Small-scale whooping cough has also continued in many countries, due in part to the waning of immune protection after childhood vaccination, necessitating the development of an improved pertussis vaccine and vaccination program. Currently, two different production platforms are being actively pursued in Korea; one is based on the aP (acellular pertussis) vaccine purified from B. pertussis containing pertussis toxoid (PT), filamentous hemagglutin (FHA) and pertactin (PRN), and the other is based on the recombinant aP (raP), containing genetically detoxified pertussis toxin ADP-ribosyltransferase subunit 1 (PtxS1), FHA, and PRN domain, expressed and purified from recombinant E. coli. aP components were further combined with diphtheria and tetanus vaccine components as a prototype DTaP vaccine by GC Pharma (GC DTaP vaccine). We evaluated and compared the immunogenicity and the protective efficacy of aP and raP vaccines in an experimental murine challenge model: humoral immunity in serum, IgA secretion in nasal lavage, bacterial clearance after challenge, PTx (pertussis toxin) CHO cell neutralization titer, cytokine secretion in spleen single cell, and tissue resident memory CD4+ T cell (CD4+ TRM cell) in lung tissues. In humoral immunogenicity, GC DTaP vaccines showed high titers for PT and PRN and showed similar patterns in nasal lavage and IL-5 cytokine secretions. The GC DTaP vaccine and the control vaccine showed equivalent results in bacterial clearance after challenge, PTx CHO cell neutralization assay, and CD4+ TRM cell. In contrast, the recombinant raP vaccine exhibited strong antibody responses for FHA and PRN, albeit with low antibody level of PT and low titer in PTx CHO neutralization assay, as compared to control and GC DTaP vaccines. The raP vaccine provided a sterile lung bacterial clearance comparable to a commercial control vaccine after the experimental challenge in murine model. Moreover, raP exhibited a strong cytokine response and CD4+ TRM cell in lung tissue, comparable or superior to the experimental and commercial DTaP vaccinated groups. Contingent on improving the biophysical stability and humoral response to PT, the raP vaccine warrants further development as an effective alternative to aP vaccines for the control of a pertussis outbreak.

Pertussis seroprevalence in mother-infant pairs from India: role of maternal immunisation

OBJECTIVE

To evaluate pertussis antibody status of pregnant women and their newborns, and the impact of antenatal immunisation.

DESIGN

Observational study.

SETTING

Hospitals in urban western India.

PARTICIPANTS

Pregnant women and their newborns.

METHODS

Pertussis antibody titres in mothers and their newborns were determined. Vaccinated and unvaccinated mothers and their newborns were compared for baseline characteristics, geometric mean titres (GMTs) and placental transfer ratio of antibodies. Multivariate logistic regression was performed to understand the influence of different factors on protective antibody titres.

RESULTS

Of 284 mother-infant pairs, 75 mothers and 73 of their newborns were seropositive for anti-pertussis toxin (PT) IgG antibodies. 94 women were vaccinated in pregnancy; 51 (54.3%) of these mothers and newborns were PT IgG positive, compared with 24 (12.3%) of the women (and 22 newborns) not vaccinated in pregnancy. Women vaccinated in pregnancy and their newborns had higher GMT (30.88 and 32.54 IU/mL), compared with women who were not vaccinated (12.63%, 2.24 IU/mL) and their newborns (11.58%, 2.53 IU/mL). Placental transfer ratios in newborns of mothers vaccinated in pregnancy and those who had childhood immunisation or natural immunity were similar (1.05 and 1.12, respectively). Protective titres of antibodies at birth (>20 IU/mL) were observed in 72.3% vs 21% of newborns of vaccinated and unvaccinated pregnant women, respectively; influenced by mother's vaccination status and seropositivity.

CONCLUSION

Protection against pertussis is low in newborns of mothers who are only immunised during childhood. Vaccination early in pregnancy boosts maternal and neonatal immunity.

A profile of the Simplexa™ Bordetella Direct assay for the detection and differentiation of Bordetella pertussis and Bordetella parapertussis in nasopharyngeal swabs

INTRODUCTION

Pertussis is a highly contagious respiratory infection caused by Bordetella pertussis and to minor extent B. parapertussis. Despite high vaccination coverage, epidemics persist worldwide. Laboratory testing with the capacity to support increasing demand and generate fast and accurate results is needed to promptly provide treatment to mitigate symptoms, prevent transmission, and thus impact infection control and disease surveillance.

AREAS COVERED

This review will describe the features of the Simplexa™ Bordetella Direct Assay and compare this technology with other existing assays. Unmet needs and future directions will be discussed.

EXPERT COMMENTARY

Resurgence of pertussis highlights the importance of reliable and accurate diagnosis. The Simplexa™ Bordetella Direct Assay provides an easy workflow, reduced hand-on time, less risk of contamination, and rapid turnaround time. The use of efficient molecular assays in routine clinical laboratory is valuable for increasing demand, improvement of infection control, and surveillance.

Pertussis-like syndrome often not associated with Bordetella pertussis: 5-year study in a large children's hospital

Background: Recently, a resurgence of pertussis has been observed worldwide despite broad vaccination coverage. The purpose of this study was to identify the clinical characteristics and the aetiological agent of pertussis-like syndrome (PLS) in Eastern China.Methods: 1168 patients who were diagnosed with a suspected Bordetella pertussis in Shanghai Children's Hospital from 2013 to 2017 were included in the study. Clinical features and aetiologies were analysed. Aetiological analyses in sub-cohorts of age, seasons and years were also investigated.Results: 96.0% (1121) of the patients were less than 12 months old. 59.0% (689) of the patients were male. The Top 5 pathogens were respiratory syncytial virus (RSV; n = 125; 10.7%), Streptococcus pneumonia (SP; n = 109; 9.3%), Haemophilus influenzae type b (HIB; n = 86; 7.4%), Bordetella pertussis (B. pertussis; n = 84; 7.2%), and Mycoplasma pneumonia (MP; n = 80; 6.9%), respectively. The percentage of SP in the age group of 0-3 months was significantly lower than that in other age groups. The percentage of B. pertussis in the age group of 3-6 months was significantly lower than that in the group of 6-12 months. The percentage of MP in 0-3 months' group was significantly lower than that in >12 months group. RSV peaked in winter (n = 52), while HIB peaked in spring (n = 38).Conclusion: PLS occurred most often in infants. RSV, SP, HIB, B. pertussis, and MP were the most prevalent pathogens. Since patients with B. pertussis and other pathogens have similar clinical manifestations, diagnosis of pertussis should be based on both clinical symptoms and laboratory confirmation.

Identification of etiologic agents and clinical characteristics for patients suspected of having pertussis in a large Children's Hospital in China

BACKGROUND

In China, pertussis is a major health problem with an increasing incidence despite immunization efforts. Timely and accurate diagnosis is essential for the optimal management of pertussis, especially in severe cases.

METHODS

Nasopharyngeal swabs or sputum specimens were obtained from patients suspected of having pertussis on the day of hospitalization at Shanghai Children's Medical Center from December 01, 2016, to November 30, 2017. The specimens were tested with the FilmArray Respiratory Panel, a multiplex polymerase chain reaction (PCR) assay that detects 16 viruses, Bordetella pertussis (B. pertussis), Mycoplasma pneumoniae (M. pneumoniae), and Chlamydophila pneumoniae (C. pneumoniae).

RESULTS

Among the 140 children studied, 50.0% (70/140) were detected with a single pathogen, 45.0% (63/140) were detected with multiple pathogens, and 5.0% (7/140) had no detected pathogens. Forty-nine (35%, 49/140) patients tested positive for B. pertussis. Respiratory syncytial virus (RSV), parainfluenza virus (Para) and rhinovirus/enterovirus (Rhino/Entero) were the most prevalent pathogens in patients with pertussis-like syndrome. No significant differences between the groups with pertussis and pertussis-like syndrome were observed regarding the clinical symptoms. Severe cases were more frequently observed in unvaccinated, premature and pertussis/RSV co-infection patients.

CONCLUSIONS

Our study highlights the importance of the timely and accurate diagnosis of pertussis based on both clinical symptoms and laboratory methods.

Pertussis in Latin America: Recent epidemiological data presented at the 2017 Global Pertussis Initiative meeting

The Global Pertussis Initiative (GPI) is an expert scientific forum that publishes consensus recommendations for pertussis monitoring, prevention, and treatment across many regions of the world. Here, we report on the regional 2017 GPI meeting on the Americas, focusing on Latin America. Information on current pertussis epidemiology, surveillance, vaccine strategies, diagnostic capabilities, disease awareness, and major local obstacles was presented by researchers from Argentina, Brazil, Colombia, Costa Rica, El Salvador, Mexico, Peru, Puerto Rico, Uruguay, and Venezuela. Pertussis outbreaks have occurred during the last decade in the majority of participant countries and have been followed by improvements in surveillance. In the countries that introduced maternal immunization during pregnancy, a reduction in the infant case fatality rate has been detected. All countries need to maintain and improve pertussis surveillance to reach primary vaccination coverage >90%. Moreover, countries without maternal immunization programs should strongly consider them.

Understanding barriers and predictors of maternal immunization: Identifying gaps through an exploratory literature review

BACKGROUND

The Advisory Committee for Immunization Practices recommends that all pregnant women receive the seasonal influenza vaccine and the tetanus toxoid, diphtheria toxoid, and acellular pertussis (Tdap) vaccine during every pregnancy. However, vaccination coverage rates are suboptimal among pregnant women in the United States, leaving these women and their unborn children at risk of vaccine-preventable diseases and their complications.

OBJECTIVES

We sought to understand the current landscape of published literature regarding maternal immunization, including barriers to and predictors of vaccine acceptance, and identify gaps in the research in order to inform strategies for future programmatic improvement.

METHODS

We conducted a literature search using MEDLINE (OVID), PsychINFO, and CINAHL (Ebsco) databases. The search included published, English-language manuscripts that identified patient, provider, or system-level barriers to, predictors of, or interventions that improved uptake of maternal vaccines among pregnant women in the US. Studies were reviewed using an inductive thematic analysis approach.

RESULTS

We included 75 studies in our review. Pregnant women identified 25 different barriers to accepting recommended maternal immunizations; barriers related to vaccine safety perceptions were the most common. Healthcare providers identified 24 different barriers to vaccinating their pregnant patients. The most commonly cited barriers among healthcare providers were financial concerns. Eighteen different predictors of vaccine acceptance were identified. Receipt of a healthcare provider's recommendation was the factor most frequently reported as a reason for vaccination among pregnant women.

CONCLUSIONS

We were able to identify gaps in the literature regarding maternal immunization and make recommendations for future research. Efforts to address the challenges of maternal immunization in the United States should include increasing the focus on Tdap, implementing more high-level assessments of safety perceptions and associated concerns, and determining most effective interventions.

Pertussis epidemiology in Argentina: TRENDS after the introduction of maternal immunisation

Data on the impact of the recently recommended maternal pertussis vaccination are promising, but still insufficient to universalise this approach. We thus compared the epidemiological data prior to the implementation of this vaccination strategy in Argentina (2012) with the figures reported after 2012. During that 2010–2016 period, two outbreaks occurred, one in 2011 and another in 2016. In the former, the incidence was 6.9/100 000 inhabitants and the case-fatality rate 2.6%. Thereafter, a decline in incidence was detected until 2014. During 2015 and 2016 an increase in the incidence transpired, but this rise was fortunately not accompanied by one in the case fatality ratio. Indeed, in 2016 the case fatality ratio was the lowest (0.6%). Moreover, during the 2016 outbreak, the incidence (3.9/100 000 inhabitants) and the case severity detected in the most vulnerable population (infants 0–2 months) were both lower than those in 2011. Consistent with this pattern, in 2016, in the most populated province of Argentina (Buenos Aires), the case percentage with laboratory-positive results indicating a high number of symptoms (59.1% of the total cases) diminished compared with that detected in the 2011 outbreak without maternal immunisation (71.9%). Using the mathematical model of pertussis transmission we previously designed, we assessed the effect of vaccination during pregnancy on infant incidence. From comparisons between the epidemiological data made through calculations, emerged the possibility that vaccinating women during pregnancy would benefit the infants beyond age 2 months, specifically in the 2–12-month cohort.

Synthesis of α-Branched Acyclic Nucleoside Phosphonates as Potential Inhibitors of Bacterial Adenylate Cyclases

Inhibition of Bordetella pertussis adenylate cyclase toxin (ACT) and Bacillus anthracis edema factor (EF), key virulence factors with adenylate cyclase activity, represents a potential method for treating or preventing toxemia related to whooping cough and anthrax, respectively. Novel α-branched acyclic nucleoside phosphonates (ANPs) having a hemiaminal ether moiety were synthesized as potential inhibitors of bacterial adenylate cyclases. ANPs prepared as bisamidates were not cytotoxic, but did not exhibit any profound activity (IC₅₀ >10 μm) toward ACT in J774A.1 macrophages. The apparent lack of activity of the bisamidates is speculated to be due to the inefficient formation of the biologically active species (ANPpp) in the cells. Conversely, two 5-haloanthraniloyl-substituted ANPs in the form of diphosphates were shown to be potent ACT and EF inhibitors with IC₅₀ values ranging from 55 to 362 nm.

Incidence of Severe and Nonsevere Pertussis Among HIV-Exposed and -Unexposed Zambian Infants Through 14 Weeks of Age: Results From the Southern Africa Mother Infant Pertussis Study (SAMIPS), a Longitudinal Birth Cohort Study

Background. Maternal vaccination with tetanus, reduced-dose diphtheria, and acellular pertussis vaccine (Tdap) could be an effective way of mitigating the high residual burden of infant morbidity and mortality caused by Bordetella pertussis. To better inform such interventions, we conducted a burden-of-disease study to determine the incidence of severe and nonsevere pertussis among a population of Zambian infants.

Methods. Mother–infant pairs were enrolled at 1 week of life, and then seen at 2- to 3-week intervals through 14 weeks of age. At each visit, nasopharyngeal (NP) swabs were obtained from both, and symptoms were catalogued. Using polymerase chain reaction (PCR) to identify cases, and a severity scoring system to triage these into severe/nonsevere, we calculated disease incidence using person-time at risk as the denominator.

Results. From a population of 1981 infants, we identified 10 with clinical pertussis, for an overall incidence of 2.4 cases (95% confidence interval [CI], 1.2–4.2) per 1000 infant-months and a cumulative incidence of 5.2 cases (95% CI, 2.6–9.0) per 1000 infants. Nine of 10 cases occurred within a 3-month window (May–July 2015), with highest incidence between birth and 6 weeks of age (3.5 cases per 1000 infant-months), concentrated among infants prior to vaccination or among those who had only received 1 dose of Diphtheria Tetanus whole cell Pertussis (DTwP). Maternal human immunodeficiency virus (HIV) modestly increased the risk of infant pertussis (risk ratio, 1.8 [95% CI, .5–6.9]). Only 1 of 10 infant cases qualified as having severe pertussis. The rest presented with the mild and nonspecific symptoms of cough, coryza, and/or tachypnea. Notably, cough durations were long, exceeding 30 days in several cases, with PCRs repeatedly positive over time.

Conclusions. Pertussis is circulating freely among this population of Zambian infants but rarely presents with the classical symptoms of paroxysmal cough, whooping, apnea, and cyanosis. Maternal HIV appears to increase the risk, while lack of effective exposure to DTwP increased the risk.

Knowledge, attitudes, beliefs, and behaviors of pregnant women approached to participate in a Tdap maternal immunization randomized, controlled trial

Immunization with pertussis vaccine during pregnancy is recommended in a number of countries to prevent newborn deaths from whooping cough. In some jurisdictions, vaccine uptake during pregnancy is low. We undertook a survey of the knowledge, attitudes, beliefs, and behaviors of pregnant women who had been approached to participate in a randomized, controlled trial of tetanus-diphtheria-acellular pertussis (Tdap) vaccine during pregnancy. A total of 346 women completed the survey. Knowledge about pertussis and pertussis vaccine was generally low; the mean number of correct answers was 10.65 out of 19 questions. Attitudes toward maternal immunization were generally favorable; 51.7%–94.7% of women had positive responses to 10 attitudinal statements. Substantial uncertainty was shown in responses to a number of the attitudinal statements related to vaccination during pregnancy; 22.3%–45.7% neither agreed nor disagreed with the statements. Importantly, 89% of women reported that they would get immunized with pertussis vaccine during pregnancy if their physician recommended it. We conclude that a national recommendation to be immunized with pertussis vaccine during pregnancy supported by their physicians' recommendation would be well received by Canadian women.

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.

Estimating Loss of Brucella Abortus Antibodies from Age-Specific Serological Data In Elk

Serological data are one of the primary sources of information for disease monitoring in wildlife. However, the duration of the seropositive status of exposed individuals is almost always unknown for many free-ranging host species. Directly estimating rates of antibody loss typically requires difficult longitudinal sampling of individuals following seroconversion. Instead, we propose a Bayesian statistical approach linking age and serological data to a mechanistic epidemiological model to infer brucellosis infection, the probability of antibody loss, and recovery rates of elk (Cervus canadensis) in the Greater Yellowstone Ecosystem. We found that seroprevalence declined above the age of ten, with no evidence of disease-induced mortality. The probability of antibody loss was estimated to be 0.70 per year after a five-year period of seropositivity and the basic reproduction number for brucellosis to 2.13. Our results suggest that individuals are unlikely to become re-infected because models with this mechanism were unable to reproduce a significant decline in seroprevalence in older individuals. This study highlights the possible implications of antibody loss, which could bias our estimation of critical epidemiological parameters for wildlife disease management based on serological data.

A Case of Pertussis: What Emergency Health Care Providers Need to Know

Pertussis is a highly contagious acute respiratory illness. Prior to the availability of the whole-cell pertussis vaccine in the late 1940s, pertussis was one of the most common infectious diseases of childhood in the United States and a major cause of infant morbidity and mortality. Although pertussis vaccination has resulted in a substantial reduction in the disease, the incidence has been steadily increasing since the 1990s. The clinical presentation of pertussis may be variable depending on the age and immunization status of the patient. The classic presentation includes a triad of symptoms: paroxysms of coughing; an inspiratory whoop following cough; and posttussive vomiting. Those most vulnerable are the ones not yet immunized and the ones most likely to transmit the illness who may not exhibit "classic" pertussis symptoms, delaying or preventing identification and treatment. Because pertussis carries known morbidity and mortality risks, prevention and early identification are paramount.

Pertussis: Microbiology, Disease, Treatment, and Prevention

Pertussis is a severe respiratory infection caused by Bordetella pertussis, and in 2008, pertussis was associated with an estimated 16 million cases and 195,000 deaths globally. Sizeable outbreaks of pertussis have been reported over the past 5 years, and disease reemergence has been the focus of international attention to develop a deeper understanding of pathogen virulence and genetic evolution of B. pertussis strains. During the past 20 years, the scientific community has recognized pertussis among adults as well as infants and children. Increased recognition that older children and adolescents are at risk for disease and may transmit B. pertussis to younger siblings has underscored the need to better understand the role of innate, humoral, and cell-mediated immunity, including the role of waning immunity. Although recognition of adult pertussis has increased in tandem with a better understanding of B. pertussis pathogenesis, pertussis in neonates and adults can manifest with atypical clinical presentations. Such disease patterns make pertussis recognition difficult and lead to delays in treatment. Ongoing research using newer tools for molecular analysis holds promise for improved understanding of pertussis epidemiology, bacterial pathogenesis, bioinformatics, and immunology. Together, these advances provide a foundation for the development of new-generation diagnostics, therapeutics, and vaccines.

Characterization of the immune response induced by pertussis OMVs-based vaccine

For the development of a third generation of pertussis vaccine that could improve the control of the disease, it was proposed that the immune responses induced by the classic whole cell vaccine (wP) or after infection should be used as a reference point. We have recently identified a vaccine candidate based on outer membrane vesicles (OMVs) derived from the disease etiologic agent that have been shown to be safe and protective in mice model of infection. Here we characterized OMVs-mediated immunity and the safety of our new candidate. We also deepen the knowledge of the induced humoral response contribution in pertussis protection. Regarding the safety of the OMVs based vaccine (TdapOMVsBp,) the in vitro whole blood human assay here performed, showed that the low toxicity of OMVs-based vaccine previously detected in mice could be extended to human samples. Stimulation of splenocytes from immunized mice evidenced the presence of IFN-γ and IL-17-producing cells, indicated that OMVs induces both Th1 and Th17 response. Interestingly TdapOMVsBp-raised antibodies such as those induced by wP and commercial acellular vaccines (aP) which contribute to induce protection against Bordetella pertussis infection. As occurs with wP-induced antibodies, the TdapOMVsBp-induced serum antibodies efficiently opsonized B. pertussis. All the data here obtained shows that OMVs based vaccine is able to induce Th1/Th17 and Th2 mixed profile with robust humoral response involved in protection, positioning this candidate among the different possibilities to constitute the third generation of anti-pertussis vaccines.

Increasing incidence of pertussis in Brazil: a retrospective study using surveillance data

BACKGROUND

Many countries have reported an increase in the incidence of pertussis, which has become a global public health concern.

METHODS

In this study, the epidemiology of pertussis in Brazil was assessed retrospectively using surveillance data gathered from case notification forms from 2007 to 2014.

RESULTS

From 2007 to 2014, 80,068 suspected cases of pertussis were reported in Brazil. Of these, 24,612 (32 %) were confirmed by various criteria. The annual distribution of confirmed cases demonstrated a significant increase in incidence rate since 2012. A seasonal pattern in which cases occur most frequently between the end of spring and midsummer has been identified. Among the confirmed cases, 34.5 % occurred in infants aged 0-2 months, 22.4 % occurred in infants aged 3-6 months, 21 % occurred in children aged 7 months to 4 years, and 8 % were reported in adults >21 years. Of the confirmed cases, 47.2 % met only clinical criteria, 15.5 % met clinical and epidemiological criteria, and 36.6 % were confirmed in a laboratory. The overall case fatality rate was 2.1 %, reaching 4.7 % among infants aged 0-2 months. The complications most commonly reported in the notification forms were pneumonia, encephalitis, dehydration, otitis, and malnutrition. Of the confirmed cases, 23.1 % occurred in subjects who received at least 3 doses of the pertussis vaccine. Within this group, there were 1098 infants aged 7 to 15 months and 2079 children aged 16 months to 4 years. In 2012, 18 states did not achieve 95 % immunization coverage, a number that dropped to 10 and 6 in 2013 and 2014, respectively.

CONCLUSIONS

Brazil's main challenges in facing pertussis resurgence will be to offer the best quality medical attention to reduce mortality, to improve the infrastructure for laboratory diagnosis and to increase vaccination coverage. Additional studies to assess the effectiveness of the current vaccination schedule and basic research on the genetics and evolution of circulating B. pertussis strains are also needed.

Under-recognized pertussis in adults from Asian countries: a cross-sectional seroprevalence study in Malaysia, Taiwan and Thailand

Surveillance data on the burden of pertussis in Asian adults are limited. This cross-sectional study evaluated the prevalence of serologically confirmed pertussis in adults with prolonged cough in Malaysia, Taiwan and Thailand. Adults (⩾19 years) with cough lasting for ⩾14 days without other known underlying cause were enrolled from outpatient clinics of seven public and/or private hospitals. Single blood samples for anti-pertussis toxin antibodies (anti-PT IgG) were analysed and economic impact and health-related quality of life (EQ-5D) questionnaires assessed. Sixteen (5·13%) of the 312 chronically coughing adults had serological evidence of pertussis infection within the previous 12 months (anti-PT IgG titre ⩾62·5 IU/ml). Three of them were teachers. Longer duration of cough, paroxysms (75% seroconfirmed, 48% non-seroconfirmed) and breathlessness/chest pain (63% seroconfirmed, 36% non-seroconfirmed) were associated with pertussis (P < 0·04). Of the seroconfirmed patients, the median total direct medical cost per pertussis episode in public hospitals (including physician consultations and/or emergency room visits) was US$13 in Malaysia, US$83 in Taiwan (n = 1) and US$26 in Thailand. The overall median EQ-5D index score of cases was 0·72 (range 0·42–1·00). Pertussis should be considered in the aetiology of adults with a prolonged or paroxysmal cough, and vaccination programmes considered.

Pertussis Accompanying Recent Mycoplasma Infection in a 10-Year-Old Girl

Recently, the incidence of pertussis has been increasing; however, reports on mixed infection of pertussis with other respiratory pathogens are rare in highly immunized populations. We report the case of a 10-year-old girl who presented with cough, post-tussive emesis, and fever. She was subsequently diagnosed with bronchopneumonia. Although she had received five doses of diphtheria-tetanus-acellular pertussis vaccine, polymerase chain reaction of her nasopharyngeal aspirate confirmed Bordetella pertussis infection. In addition, serologic testing for Mycoplasma pneumoniae was also positive. The patient was treated with roxithromycin without any complications. This is the first report of mixed B. pertussis and M. pneumoniae infection in Korea. To avoid under-diagnosis, pertussis should be considered in patients with chronic cough even when other respiratory pathogens have been documented.

Maternal benefits of immunization during pregnancy

The US Centers for Disease Control & Prevention currently recommend routine immunization to prevent 17 vaccine-preventable diseases that occur in infants, children, adolescents, or adults. Pregnant women are at particularly high risk for morbidity and mortality related to several vaccine-preventable diseases. Furthermore, such illnesses are also associated with adverse pregnancy outcomes such as spontaneous abortion, congenital anomalies, preterm birth, and low birthweight. In addition to directly preventing maternal infection, vaccination during pregnancy may offer fetal and infant benefit through passive immunization. Several vaccines aimed at providing passive immunity to neonates are either currently recommended or in development. This article specifically addresses maternal benefits of maternal immunization following (1) vaccines recommended for all pregnant women; (2) vaccines recommended for pregnant women with particular risk factors; and (3) novel vaccines currently under development that primarily aim to at reduce infant morbidity and mortality.

Host-pathogen interaction during bacterial vaccination

Vaccines have been developed and deployed against several important bacterial pathogens of humans, including Neisseria meningitidis, Bordetella pertussis, Streptococcus pneumoniae and Mycobacterium tuberculosis. These vaccines are generally considered a successful public health measure and are effective at controlling disease symptoms and/or burden. However, a troubling consequence of recent vaccination programs has been the selection of vaccine escape mutants, whereby the pathogen displays a different repertoire of immune targets than those represented in the vaccine formulation. To address these issues of antigenic variation and bacterial evolution, continued and sustained efforts in epidemiological surveillance, vaccine development/formulation research, and understanding of the host-pathogen interaction are required.

Decennial administration in young adults of a reduced-antigen content diphtheria, tetanus, acellular pertussis vaccine containing two different concentrations of aluminium

BACKGROUND

Regular booster vaccination might be necessary throughout life to protect against pertussis infection. Nevertheless the duration of protection after booster vaccination remains unclear. In this study, antibody persistence up to 10 years after previous vaccination of adolescents (N=478) with combined reduced-antigen-content diphtheria-tetanus-acellular pertussis vaccine (dTpa, Boostrix™, GlaxoSmithKline Belgium) containing 0.5mg, 0.3mg or 0.133mg of aluminium was assessed. The immunogenicity, reactogenicity and safety of a decennial booster dTpa dose were also investigated.

METHODS

Young adults vaccinated as adolescents in the initial booster study were invited to participate in an assessment of antibody persistence at years 8.5 and 10, and to receive a dTpa booster dose at year 10 with immunogenicity assessment one month later. Those who originally received the 0.5mg or 0.3mg formulations received the same vaccine at year 10. Those in the 0.133mg group received the 0.5mg formulation. Reactogenicity and safety endpoints were captured until 30 days after booster vaccination.

RESULTS

Prior to the decennial booster at year 8.5 and year 10, all participants had seroprotective antibodies for diphtheria (ELISA or neutralisation assay) and tetanus. At least 77.8% were seropositive for anti-pertussis toxin (PT) antibodies at year 8.5 and 82.8% at year 10. All participants were seropositive for antibodies for filamentous haemagglutinin and pertactin at both time points. The decennial booster dose induced robust increases in antibody GMCs to all antigens. The post-booster anti-PT geometric mean concentration was 82.5EL.U/ml (95%CI 67.0-101.6) and 124.0 (103.5-148.5) in the 0.3mg and 0.5mg groups, respectively. The reactogenicity and safety profile of the decennial booster dose was consistent with the known safety profile of dTpa. No serious adverse events were reported.

CONCLUSIONS

Decennial booster vaccination with either of the two licensed formulations of dTpa was highly immunogenic and well tolerated in young adults. Either formulation could be confidently used as a decennial booster. This study is registered at www.clinicaltrials.govNCT01147900.

Bordetella parapertussis outbreak in Bisham, Pakistan in 2009–2010: fallout of the 9/11 syndrome

Pertussis or whooping cough is a highly contagious community disease mainly caused by Bordetella pertussis and B. parapertussis. We report a minor outbreak of whooping cough (2009–2010) in symptomatic subjects from Bisham, near Swat, Khyber Pukhtoonkhawa province, Pakistan. Interestingly, our results show that all the culture-positive isolates (n = 21) collected from children (average age 3·46 years), were identified as B. parapertussis after routine identification tests and PCR IS481, IS1001 and IS1002. Furthermore, in the affected patients, none had received immunization with diphtheria-pertussis-tetanus (DTPw) vaccine. Therefore, the possibility of the re-emergence of the disease due to limitation of basic health services as a result of the political unrest due to the 9/11 situation is also examined. Moreover, we discuss the importance of vaccinating both adults and children with DTPwPaw vaccine containing both organisms for better protection.

Vaccinations for pregnant women

In the United States, eradication and reduction of vaccine-preventable diseases through immunization has directly increased life expectancy by reducing mortality. Although immunization is a public priority, vaccine coverage among adult Americans is inadequate. The Institute of Medicine, the Community Preventive Services Task Force, and other public health entities have called for the development of innovative programs to incorporate adult vaccination into routine clinical practice. Obstetrician-gynecologists are well suited to serve as vaccinators of women in general and more specifically pregnant women. Pregnant women are at risk for vaccine-preventable disease-related morbidity and mortality and adverse pregnancy outcomes, including congenital anomalies, spontaneous abortion, preterm birth, and low birth weight. In addition to providing direct maternal benefit, vaccination during pregnancy likely provides direct fetal and neonatal benefit through passive immunity (transplacental transfer of maternal vaccine-induced antibodies). This article reviews: 1) types of vaccines; 2) vaccines specifically recommended during pregnancy and postpartum; 3) vaccines recommended during pregnancy and postpartum based on risk factors and special circumstances; 4) vaccines currently under research and development for licensure for maternal-fetal immunization; and 5) barriers to maternal immunization and available patient and health care provider resources.

Immunogenicity, safety, and antibody persistence at 3, 5, and 10 years postvaccination in adolescents randomized to booster immunization with a combined tetanus, diphtheria, 5-component acellular pertussis, and inactivated poliomyelitis vaccine administered with a hepatitis B virus vaccine concurrently or 1 month apart

An understanding of the antibody persistence elicited by a combined tetanus, diphtheria, 5-component acellular pertussis, and inactivated poliovirus vaccine (Tdap-IPV) after adolescent vaccination is important to optimize booster dosing intervals. Our objectives were to compare the safety and immunogenicity of Tdap-IPV coadministered with hepatitis B vaccine (HepB) and sequential administration and evaluate humoral immunity at 3, 5, and 10 years after Tdap-IPV vaccination in adolescents. This phase II randomized, controlled, and open-label study enrolled 280 11- to 14-year-old adolescents with up to 10 years postvaccination follow-up. Group 1 (n = 145) received Tdap-IPV, followed by a HepB dose 1 month later, and group 2 (n = 135) received both vaccines simultaneously. No consistent increases in solicited reactions or unsolicited adverse events occurred with coadministration. All vaccinees attained seroprotective antibody levels at ≥0.01 IU/ml for diphtheria and tetanus, at a ≥1:8 dilution for poliovirus (serotypes 1, 2, and 3), and ≥10 mIU/ml for hepatitis B at 1 month postvaccination. Clinically relevant immunologic interactions did not occur with coadministration. For pertussis, all participants achieved seropositivity levels (at or above the lower limit of quantitation), and 72.7% to 95.8% had 4-fold increases in pertussis antibodies at 1 month postvaccination. At 10 years postvaccination, the remaining participants (62.8% of the original cohort) maintained seroprotective levels of ≥0.01 IU/ml for diphtheria and tetanus, a ≥1:8 dilution for all 3 poliovirus serotypes, and 74.1% to 98.2% maintained pertussis seropositivity levels depending on the antigen tested. There were no differences between the groups. These results support the coadministration of Tdap-IPV and HepB to adolescents and suggest that vaccination with Tdap-IPV can offer protection for 10 years after an adolescent booster vaccination.

Health care worker exposures to pertussis: missed opportunities for prevention

OBJECTIVE

Pediatric health care workers (HCWs) are at particular risk for pertussis exposure, infection, and subsequent disease transmission to susceptible patients. This cross-sectional study describes the epidemiology of occupational exposures to pertussis and identifies factors that may inform interventions to promote effective implementation of infection prevention and control (IPC) guidelines.

METHODS

We abstracted data from occupational health (OH) and IPC records for pertussis cases that resulted in an exposure investigation in a large quaternary pediatric care network, January 1, 2002 to July 18, 2011. We calculated the frequency of occupational exposures and measured associated characteristics. To assess the frequency of potential missed exposures, we reviewed electronic health record (EHR) data identifying laboratory-confirmed pertussis cases not documented in OH or IPC records.

RESULTS

A total of 1193 confirmed HCW pertussis exposures were associated with 219 index cases during the study period. Of these, 38.8% were infants <6 months old and 7 were HCWs. Most (77.5%) of exposures occurred in the emergency department or an ambulatory site; 27.0% of exposures occurred after documented initiation of IPC precautions. We identified 450 laboratory-confirmed pertussis cases through EHR review, of which 49.8% (N = 224) had no OH or IPC investigation. The majority of uninvestigated cases (77.2%) were from ambulatory sites.

CONCLUSIONS

Occupational exposures to pertussis occur frequently in pediatric health care settings despite appropriate IPC guidelines. Interventions are needed to ensure consistent implementation of IPC practices and timely identification and reporting of pertussis index cases to prevent HCW exposures and potential transmission to patients.

Infant hospitalizations for pertussis before and after Tdap recommendations for adolescents

OBJECTIVE

Recent universal vaccination efforts among children in the United States have markedly changed hospitalization patterns for many vaccine-preventable diseases. Infants with pertussis often require hospitalization to monitor for potentially life-threatening respiratory failure. In 2006, tetanus-diphtheria-acellular pertussis (Tdap) vaccination was recommended for universal administration to adolescents, a known source of pertussis in infants. By 2011, 78% of adolescents in the United States had received Tdap. We sought to understand if patterns of pertussis hospitalization for infants changed with adoption of Tdap vaccination among adolescents.

METHODS

Infants (aged <1 year) diagnosed with pertussis were identified in the Nationwide Inpatient Sample by using diagnostic codes. We used variance-weighted least-squares regression over preimplementation years (2000-2005) to estimate pertussis hospitalization patterns if Tdap had not been available. We compared expected hospitalization rates with observed rates for 2008-2011. Two years (2006 and 2007) were excluded from analysis during early Tdap implementation.

RESULTS

The incidence of hospitalization for pertussis in 2000 was 5.82 (95% confidence interval: 4.51-7.13) discharges per 10,000 infants in the US population. The rate increased during pre-Tdap years by a mean of 0.64 pertussis discharges per 10,000 infants per year (P for trend = .004). Observed hospitalization rates for pertussis among infants were significantly lower than expected in 2008, 2009, and 2011, but in 2010 the observed and expected rates of hospitalization were not significantly different.

CONCLUSIONS

Adolescent Tdap vaccination appears to be partially effective in preventing pertussis hospitalizations among infants. However, broader Tdap immunization coverage may be necessary to achieve sustainable reductions in infant pertussis burden.

Seroepidemiology of pertussis in a cross-sectional study of an adult general population in Denmark

An increase in pertussis has been observed in several countries over the last decades, especially in adult populations. The seroprevalence of pertussis was determined in a cross-sectional study of the adult population in the Copenhagen area, Denmark, conducted between 2006 and 2008. Specific IgG antibodies against pertussis toxin (PT) were measured in 3440 persons resulting in an age-standardized seroprevalence of 3·0% (95% confidence interval 1·9–4·7) using an IgG anti-PT cut-off of 75 IU/ml. By using antibody decay profiles from longitudinal data the estimated seroincidence was 143/1000 person-years. In contrast, an incidence of 0·03/1000 person-years was estimated from the official data of notified cases during the same period. Of the investigated risk factors, only age and education were significantly associated with pertussis infection. This study indicates that pertussis is highly underestimated in the adult population in Denmark, which has implications for future prevention strategies, including raising the awareness of pertussis.

Nosocomial pertussis in neonatal units

Pertussis remains a public health concern in many countries despite high vaccination coverage rates. Nosocomial outbreaks of pertussis continue to occur in neonatal units. Neonates and young infants admitted to neonatal intensive care units constitute a pool of susceptible high-risk patients given their prematurity, inadequate immune response and the fact that they are too young to have completed their primary vaccination series against pertussis. This article reviews nosocomial pertussis in neonates and infants, focusing on the role of healthcare workers (HCWs). Outbreaks in neonatal units are often traced to HCWs and are associated with serious morbidity or even a fatal outcome among susceptible young infants. A high index of suspicion is required for early recognition and isolation of patients admitted with suspected or proven pertussis, as well as for HCWs with a compatible clinical syndrome, regardless of vaccination status. Contact investigation is also essential in order to guide administration of post-exposure prophylaxis. Recommendations for a booster vaccination for HCWs are in place in several countries; however, the need of HCWs for lifelong immunity against pertussis cannot be fulfilled by the current vaccine.

Deciphering the impacts of vaccination and immunity on pertussis epidemiology in Thailand

Pertussis is a highly infectious respiratory disease that is currently responsible for nearly 300,000 annual deaths worldwide, primarily in infants in developing countries. Despite sustained high vaccine uptake, a resurgence in pertussis incidence has been reported in a number of countries. This resurgence has led to critical questions regarding the transmission impacts of vaccination and pertussis immunology. We analyzed pertussis incidence in Thailand--both age-stratified and longitudinal aggregate reports--over the past 30 y. To dissect the contributions of waning pertussis immunity and repeat infections to pertussis epidemiology in Thailand following a pronounced increase in vaccine uptake, we used likelihood-based statistical inference methods to evaluate the support for multiple competing transmission models. We found that, in contrast to other settings, there is no evidence for pertussis resurgence in Thailand, with each model examined pointing to a substantial rise in herd immunity over the past 30 y. Using a variety of empirical metrics, we verified our findings by documenting signatures of changing herd immunity over the study period. Importantly, this work leads to the conclusion that repeat infections have played little role in shaping pertussis epidemiology in Thailand. Our results are surprisingly emphatic in support of measurable impact of herd immunity given the uncertainty associated with pertussis epidemiology.

Infant pertussis and household transmission in Korea

A recent resurgence of pertussis has raised public health concerns even in developed countries with high vaccination coverage. The aim of this study was to describe the clinical characteristics of infant pertussis, and to determine the relative importance of household transmission in Korea. The multicenter study was prospectively conducted from January 2009 to September 2011. We identified the demographic and clinical data from these patients and performed the diagnostic tests for pertussis in their household contacts. Twenty-one patients with confirmed pertussis were included in the analysis. All infections occurred in infants younger than 6 months of age (mean age, 2.5 months) who had not completed the primary DTaP vaccination except for one patient. Infants without immunization history had a significant higher lymphocytosis and longer duration of hospital stay compared to those with immunization. All were diagnosed with PCR (100%), however, culture tests showed the lowest sensitivity (42.9%). Presumed source of infection in household contacts was documented in 85.7%, mainly parents (52.6%). Pertussis had a major morbidity in young infants who were not fully immunized. Household members were responsible for pertussis transmission of infants in whom a source could be identified. The control of pertussis through booster vaccination with Tdap in family who is taking care of young infants is necessary in Korea.

Seroprevalence of pertussis in Senegal: a prospective study

BACKGROUND

Pertussis, also known as whooping cough, is a vaccine-preventable respiratory disease caused by Bordetella pertussis infection, against which Senegalese children are immunized with the diphtheria-tetanus-whole cell pertussis vaccine (DTwP). Seroepidemiology of pertussis has been widely described in industrialized countries, but rare are the studies referring to it in developing countries.

METHODS

We conducted a longitudinal survey in Northern Senegal to investigate the epidemiology of B. pertussis by evaluating the IgG antibody (Ab) response against pertussis toxin (PT). A cohort of 410 children aged 1 to 9 from five villages in the Middle Senegal River Valley were followed-up for 18 months. During that period, five visits were made to assess the immunological status of the children.

PRINCIPAL FINDINGS

PT-specific IgG responses were significantly different according to age. Until the age of 3, there was a decrease in the Ab response, which then increased in the older groups. Assessment of IgG antibodies to PT (IgG-PT) suggested evidence of recent exposures to the pathogen. Surprisingly, in one of the five villages the average Ab response to PT was very low at all ages during the first 6 months of the study. At the third visit, IgG-PT concentrations peaked to very high levels, to slightly decline at the end of the survey. This indicates an outbreak of B. pertussis, whereas in the other villages a pertussis endemic profile could be observed.

CONCLUSIONS

Pertussis is endemic in Northern Senegal despite the introduction of vaccination. The circulation of the bacteria seems to differ between geographic locations and over time. A more complete understanding of the epidemiology of pertussis and its environmental determinants could provide information to adapt vaccination programs.

Pertussis Epidemiology in Greece and Emerging Risk Groups during the Vaccination Era (1980-2008)

To study the epidemiology of pertussis in Greece and epidemiologic changes throughout a period of twenty-nine years, we conducted a retrospective analysis of available data of pertussis cases for the past twenty-nine years (1980-2008) and a prospective analysis of hospitalized pertussis cases from a children's hospital in Athens for eight years (2001-2008). From 1980 through 2008, the incidence of pertussis in Greece declined from 11.2 to 0.05 cases per 100,000. Epidemic cycles occurring every 3 to 5 years were observed. Since pertussis circulation cannot be fully controlled by present immunization programs, efforts should be made to vaccinate infants at the recommended age, early diagnose, treatment as well as contact tracing of pertussis cases. Control of pertussis in social susceptible populations is necessary. A national program with adolescent and adult booster could decrease the circulation of B. pertussis. Despite an overall decrease for pertussis cases, pertussis is still a present and future challenge of public health service in Greece.

Increased risk of pertussis in patients with asthma

BACKGROUND

The recent pertussis outbreak in California highlights the effect of pertussis on public health. In 2004, a pertussis outbreak occurred in Olmsted County, Minnesota, despite a high vaccine uptake. This outbreak provided a natural experiment to assess the relationship between asthma and pertussis.

OBJECTIVE

We sought to determine whether asthmatic subjects have a higher risk of pertussis than nonasthmatic subjects.

METHODS

We conducted a population-based case-control study. There were 223 pertussis cases identified by means of PCR in 2004 and 2005. We identified age- and sex-matched control subjects from 5537 patients with negative test results for pertussis. We conducted a comprehensive medical record review and applied predetermined criteria to ascertain asthma status. Conditional logistic regression was fit to assess the effect of asthma status on the risk of pertussis.

RESULTS

Of the 223 subjects, 164 were eligible for the study, and 328 matched control subjects (1:2 matching) were enrolled. Of these 164 subjects, 50% were male, and 82% were white. The median age at the index date of pertussis was 14 years. Sixty-two (38%) of the 164 cases had asthma before the index date of pertussis compared with 85 (26%) of the 328 control subjects (odds ratio, 1.73; 95% CI, 1.12-2.67; P = 013). The population attributable risk percentage of asthma for risk of pertussis was 17%.

CONCLUSIONS

Given the high prevalence of asthma and the ongoing risk of pertussis throughout the United States, consideration of defining asthmatic subjects as a target group for pertussis vaccination (eg, replacing decennial tetanus-diphtheria booster with tetanus, diphtheria, and acellular pertussis vaccine for adolescents and adults) should be given.

Bordetella pertussis IgG and IgA antibodies seroprevalence among 1-35 y-old population: the role of subclinical pertussis infection

OBJECTIVE

To determine age-dependent pertussis specific IgG and IgA antibodies seroprevalence in apparently healthy subjects.

METHODS

A total of 595 healthy 1-35-y-old individuals divided into 5 different age groups were selected from Sari district. Antipertussis IgG and IgA antibodies levels were measured quantitatively by ELISA method. Positive sera for IgA and also IgG titer ≥150 were considered for recent pertussis infection.

RESULTS

High seroprevelence levels (72% and 71%) were observed among preschool (<7 y) children. After decreasing the seroprevelence rates significally to lowest level (54.4%) among school aged (7-11 y), the rates increased again to the highest levels of 60% and 73% at adulthood (P = 0.03 and P = 0.003). In total, 1.55% of study subjects were IgA positive, and 5.7% showed high IgG titers.

CONCLUSIONS

The present study reveals, vaccine induced immunity has decreased among school-aged children and natural pertussis infection is common among adolescent and young adults. Also, asymptomatic/sub-clinical recent pertussis infection was prevalent among studied population. These findings necessitate developing new strategies to reduce and control pertussis infection in Iran.

Humoral immunity 10 years after booster immunization with an adolescent and adult formulation combined tetanus, diphtheria, and 5-component acellular pertussis vaccine

Persistence of antibodies after a single dose of Tdap vaccine (tetanus, diphtheria, and 5-component acellular pertussis vaccine) was evaluated in a follow-up study 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 concentrations. Humoral immune responses to all antigens were robust 1 month after initial immunization, decreased at subsequent measurements, but continued to exceed pre-immunization levels 1, 3, 5, and 10 years later. Protective levels of diphtheria and tetanus antitoxin persisted in 99.3% of adolescents 10 years after a booster dose of Tdap. Seropositivity to 1 or more pertussis antigens also persisted in most adolescents for 10 years. Although tetanus antitoxin responses were similar in adults to those observed in adolescents, diphtheria antitoxin titers were lower, reflecting the fact that a smaller proportion of adults had received diphtheria toxoid in the previous 10 years compared to adolescents. These data will contribute to the selection of the optimal interval for repeat doses of Tdap.

Comparative study of different sources of pertussis toxin (PT) as coating antigens in IgG anti-PT enzyme-linked immunosorbent assays

In an effort to improve the reliability and reproducibility of serological assays for Bordetella pertussis, a collaborative study was conducted to compare four different sources of pertussis toxin (PT) as coating antigens in the immunoglobulin G (IgG) anti-PT enzyme-linked immunosorbent assay (ELISA). Four sources of PT were used as coating antigens in the IgG anti-PT ELISA in four different testing laboratories (labs A to D) to determine whether the different antigen preparations and different laboratories influenced assay results. A panel of 60 sera consisting of deidentified human specimens from previous vaccination trials of healthy adults and infants and clinical specimens from outbreak settings was tested. In the four laboratories, each sample was tested three times with the four PT antigens according to the standard coating optimization and IgG anti-PT ELISA testing procedures used in that laboratory. Differences among the antigens, as well as intra- and interlaboratory variability, were evaluated. Excellent agreement was observed with the test panel results among the four antigens within each laboratory. Concordance correlation coefficient (r(c)) measurements among the different antigens ranged from 0.99, 0.99 to 1.00, 1.00, and 0.97 to 1.00 for labs A to D, respectively. The comparisons between pairs of laboratories also indicated a high degree of concordance for each PT preparation, with r(c) measurements between 0.90 and 0.98, 0.93 and 0.99, 0.92 and 0.98, and 0.93 and 0.99 for antigens 1 to 4, respectively. Relatively minor differences in results were observed among laboratories or among antigens, suggesting that the four PT antigens are quite similar and could be considered for acceptance in harmonized immunoassays used for serodiagnosis or vaccine evaluation.

Infectious disease

Athletes are susceptible to the same infections as the general population. However, special considerations often need to be taken into account when dealing with an athlete who has contracted an infectious disease. Health care providers need to consider how even common illnesses can affect an athlete's performance, the communicability of the illness to team members, and precautions/contraindications related to athletic participation. Recent advances in the prevention, diagnosis, and/or management of frequently encountered illnesses, as well as certain conditions that warrant special attention in the athletic setting, are discussed in detail.

The incidence of pertussis hospitalizations among Japanese infants: excess hospitalizations and complications?

We examined pertussis hospitalizations among infants aged <1 year between 2006 and 2008 using the nationwide inpatient database in Japan. A total of 660 infants hospitalized for pertussis were identified. Peak incidence occurred at age 1 month and infants aged 0-2 months (too young for pertussis vaccination) and ≥3 months (eligible for at least one dose of vaccination) accounted for 44·5% and 55·5% of hospitalizations, respectively. Complications related to pertussis were found in 165 (25·0%) cases, including one death; the age at admission did not differ significantly between patients with and those without complications (mean age 4·1 vs. 4·5 months, P=0·12). Seventeen patients required mechanical ventilation. Of the 17 cases, 14 infants were aged <3 months and three infants were aged ≥3 months. Our findings highlight that the vaccination schedule against pertussis may often be delayed in Japan.

Tdap5 vaccine (Covaxis): a review of its use as a single-booster immunization for the prevention of tetanus, diphtheria, and pertussis in children (aged 4 years), adolescents, and adults

Covaxis (also licensed as Triaxis or Adacel in individual countries) is a combined tetanus toxoid, reduced diphtheria toxoid, five component acellular pertussis (namely detoxified pertussis toxin, filamentous hemagglutinin, pertactin, and fimbriae types 2 and 3) vaccine for the prevention of diphtheria, tetanus, and pertussis. It is approved for use in Europe as a single intramuscular booster dose in children (aged ≥ 4 years), adolescents, and adults, and in the US it is approved for use in individuals aged 11-64 years. In large, randomized, controlled clinical trials conducted in the UK and North America, a single intramuscular booster dose of Covaxis induced robust immune responses for all of its component antigens when given to children (aged ≥ 4 years), adolescents, and adults. In addition, Covaxis vaccine was safe and generally well tolerated in terms of solicited and unsolicited local injection-site and systemic adverse events, most of which were of mild intensity and resolved without sequelae. Furthermore, the immunogenicity of each individual component and the reactogenicity of Covaxis vaccine in children, adolescents, and adults was generally similar to that of comparator vaccines. Despite being a vaccine-preventable disease and having >90% primary vaccination coverage worldwide, pertussis remains uncontrolled, particularly amongst adolescents and adults. Given the changing epidemiology of pertussis and the requirement to reduce infection in adolescents and adults (including healthcare workers) and thereby prevent transmission of the disease from these individuals to very young infants, the new 'cocoon strategy' recommended in current vaccination guidelines has become a key strategy in the management of morbidity and mortality associated with pertussis. This strategy focuses on the immunization of healthcare workers, and the parents and family members of infants who are too young to have undergone primary immunization, so as to prevent the transmission of pertussis to these young at-risk infants. The implementation of the 'cocoon strategy' may finally give countries the ability to control pertussis infections in these at-risk infants and ultimately provide the desired herd immunity against pertussis. In line with this strategy, a booster dose of Covaxis vaccine provides a valuable option to reduce pertussis morbidity and mortality, and to maintain seroprotection against diphtheria and tetanus in children (aged ≥ 4 years), adolescents, and adults.