Clinical practice. Pertussis--not just for kids

Understanding the impact of adult pertussis and current approaches to vaccination: A narrative review and expert panel recommendations

Pertussis has several notable consequences, causing economic burden, increased strain on healthcare facilities, and reductions in quality of life. Recent years have seen a trend toward an increase in pertussis cases affecting older children and adults. To boost immunity, and protect vulnerable populations, an enduring approach to vaccination has been proposed, but gaps remain in the evidence surrounding adult vaccination that are needed to inform such a policy. Gaps include: the true incidence of pertussis and its complications in adults; regional variations in disease recognition and reporting; and incidence of severe disease, hospitalizations, and deaths in older adults. Better data on the efficacy/effectiveness of pertussis vaccination in adults, duration of protection, and factors leading to poor vaccine uptake are needed. Addressing the critical evidence gaps will help highlight important areas of unmet need and justify the importance of adult pertussis vaccination to healthcare professionals, policymakers, and payers.

Bordetella pertussis infection following relaxation of COVID-19 non-pharmaceutical interventions in 2021-2023 in Vancouver metropolitan area, British Columbia, Canada

BACKGROUND

We recently reported a near disappearance of B. pertussis and a decline in anti-B. pertussis antibodies during the peak implementation of Coronavirus disease 2019 (COVID-19) non-pharmaceutical interventions (NPI) in 2021 in British Columbia (BC), Canada. During 2021-2023, incidence of reported B. pertussis cases remained low in BC at < 1/100,000 population. This study determined how serological evidence of B. pertussis changed after the gradual relaxation of NPI between 2021-2023.

METHODS

Randomly selected blood samples from school staff 25-51 years old (n = 65) were collected yearly between 2021-2023 in the Vancouver metropolitan area, BC, Canada, and tested for anti-pertussis toxin (PT) IgG levels. Serological evidence of B. pertussis infection (thereafter "seroconversion") was defined as a quantifiable anti-PT IgG levels in subjects with anti-PT IgG levels below lower limit of quantification in the preceding year or a > 4-fold increase in anti-PT IgG levels between two subsequent years. Samples were also tested for anti-diphtheria toxoid (DT) IgG, and similar seroconversion criteria were applied to exclude seroconversion due to vaccination with tetanus-diphtheria-acellular-pertussis (Tdap).

RESULTS

Three subjects met seroconversion criteria for anti-PT IgG between 2021 and 2022 and 9 between 2022 and 2023, yielding a seroconversion rate of 4.6 /100 person-years and 14.9/100 person-years, P = 0.127, respectively. None of the subjects met the criteria for vaccination with Tdap. The geometric mean concentration of anti-PT IgG showed a statistically significant decrease in 2022 compared with 2021, 4.8 IU/mL IU/ml (95 % confidence interval [CI], 3.8-5.9) vs. 6.4 IU/ml (95 % CI, 4.9-8.2; p = 0.001), followed by a statistically significant increase in 2023 compared with 2022 6.5 IU/ml (95 % CI, 4.9-8.5) vs. 4.8 IU/ml (95 % CI, 3.8-5.9; p = 0.0006), respectively.

DISCUSSION

Serological evidence of B. pertussis increased between 2022 and 2023 despite low reported cases, which suggests that B. pertussis circulation resumed after relaxing of COVID-19 NPI.

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.

Safety and Clinical Benefits of Adacel® and Adacel®-Polio Vaccination in Pregnancy: A Structured Literature Review

Vaccination in pregnancy using a tetanus toxoid, reduced dose diphtheria toxoid, and reduced dose acellular pertussis (Tdap) vaccine is important for prevention of severe pertussis disease in young infants. The objectives of this systematic literature review were to search for original research studies evaluating the vaccine effectiveness, immunogenicity, and safety of Adacel®/Adacel-Polio® used during pregnancy to prevent pertussis disease in young infants. Medical databases used included EMBASE, BIOSIS Previews, and Chemical Abstracts, with search terms related to pregnancy, vaccines/immunization, safety, pertussis, effectiveness/efficacy, and immune response; other potentially eligible reports were included where applicable. Search results were restricted to literature published from 1 January 1995 to 26 July 2021. A total of 2021 articles and 4 other reports were identified for primary review. A total of 49 publications qualified for inclusion after primary and secondary reviews. Effectiveness studies of Adacel or Adacel-Polio given in pregnancy consistently showed high levels of protection from pertussis disease in the newborn (vaccine effectiveness: 91-93%). In immunogenicity studies, the response in pregnant women was consistent with that of non-pregnant women. Infants of mothers vaccinated with Adacel or Adacel-Polio in pregnancy had higher anti-pertussis antibody levels at birth and at 2 months of age compared to infants born to women vaccinated with comparator vaccines, placebo, or those not vaccinated during pregnancy. There was evidence of a slightly decreased response to primary pertussis vaccination in infants of mothers vaccinated with Adacel or Adacel-Polio, but this was not thought to be clinically significant. In safety studies, Adacel or Adacel-Polio vaccination was well tolerated by pregnant woman and not associated with pregnancy, postpartum, or neonatal complications. In conclusion, Adacel or Adacel-Polio vaccination in pregnancy is highly effective in protecting young infants from pertussis disease, with a favorable safety profile for both pregnant women and their infants.

Immunogenicity and safety of BPZE1, an intranasal live attenuated pertussis vaccine, versus tetanus-diphtheria-acellular pertussis vaccine: a randomised, double-blind, phase 2b trial

BACKGROUND

Bordetella pertussis epidemics persist as transmission remains unabated despite high acellular pertussis vaccination rates. BPZE1, a live attenuated intranasal pertussis vaccine, was designed to prevent B pertussis infection and disease. We aimed to assess the immunogenicity and safety of BPZE1 compared with the tetanus-diphtheria-acellular pertussis vaccine (Tdap).

METHODS

In this double-blind, phase 2b trial at three research centres in the USA, healthy adults aged 18-50 years were randomly assigned (2:2:1:1) via a permuted block randomisation schedule to receive BPZE1 vaccination followed by BPZE1 attenuated challenge, BPZE1 vaccination followed by placebo challenge, Tdap followed by BPZE1 attenuated challenge, or Tdap followed by placebo challenge. On day 1, lyophilised BPZE1 was reconstituted with sterile water and given intranasally (0·4 mL delivered to each nostril), whereas Tdap was given intramuscularly. To maintain masking, participants in the BPZE1 groups received an intramuscular saline injection, and those in the Tdap groups received intranasal lyophilised placebo buffer. The attenuated challenge took place on day 85. The primary immunogenicity endpoint was the proportion of participants achieving nasal secretory IgA seroconversion against at least one B pertussis antigen on day 29 or day 113. Reactogenicity was assessed up to 7 days after vaccination and challenge, and adverse events were recorded for 28 days after vaccination and challenge. Serious adverse events were monitored throughout the study. This trial is registered with ClinicalTrials.gov, NCT03942406.

FINDINGS

Between June 17 and Oct 3, 2019, 458 participants were screened and 280 were randomly assigned to the main cohort: 92 to the BPZE1-BPZE1 group, 92 to the BPZE1-placebo group, 46 to the Tdap-BPZE1 group, and 50 to the Tdap-placebo group. Seroconversion of at least one B pertussis-specific nasal secretory IgA was recorded in 79 (94% [95% CI 87-98]) of 84 participants in the BPZE1-BPZE1 group, 89 (95% [88-98]) of 94 in the BPZE1-placebo group, 38 (90% [77-97]) of 42 in the Tdap-BPZE1 group, and 42 (93% [82-99]) of 45 in the Tdap-placebo group. BPZE1 induced broad and consistent B pertussis-specific mucosal secretory IgA responses, whereas Tdap did not induce consistent mucosal secretory IgA responses. Both vaccines were well tolerated, with mild reactogenicity and no serious adverse events related to study vaccination.

INTERPRETATION

BPZE1 induced nasal mucosal immunity and produced functional serum responses. BPZE1 has the potential to avert B pertussis infections, which ultimately could lead to reduced transmission and diminished epidemic cycles. These results should be confirmed in large phase 3 trials.

FUNDING

ILiAD Biotechnologies.

Seroepidemiology of pertussis in the east of China: Estimates of incidence of infection in adolescents and adults pre- and post-COVID-19

Introduction

The dramatic decrease in the number of reported cases of pertussis during COVID-19 pandemic has been underestimated. The objective was to compare the estimated incidence rate of pertussis in populations pre- and post-COVID-19 pandemic by analyzing the anti-pertussis toxin (anti-PT) IgG and anti-filamentous hemagglutininant (anti-FHA) IgG antibodies in healthy Chinese population from 2018 to 2021.

Methods

All serum samples (N = 1,000) were collected from healthy population (aged ≥ 15 years) who attended an annual monitoring project of antibody levels in Jiangsu province in 2018-2021 were measured by ELISA.

Results

The positive rates of anti-PT IgG and anti-FHA IgG antibodies were 11.4% (114/1,000) and 20.2% (202/1,000) (≥40 IU/ml), the GMC were 17.25 (95% CI: 15.49-19.03) IU/mL and 24.94 (95% CI: 22.73-27.16) IU/mL in the study population, respectively. The percentage of participants with anti-PT IgG antibodies higher than 40 IU/mL was 5.20% (11/212) in 2018, 5.5% (19/348) in 2019, 21.2% (46/217) in 2020 and 17.0% (38/223) in 2021, respectively. The non-detectable rate (<5 IU/mL) of anti-PT IgG antibodies was 16.9, 17.7, 28.1, and 37.3% in 2018, 2019, 2020, and 2021, respectively. We assumed that the infection occurred within 58.6 days, and based on the overall proportion (2.9%) of individuals with anti-PT IgG antibody ≥100 IU/ml, the incidence rate (/100) was estimated by the formula to be 18.08 (95% CI: 12.40-26.11). In addition, the estimated incidence of Post-COVID-19 was higher than that of Pre-COVID-19 (36.33/100 vs. 12.84/100), and the difference was statistically significant (p < 0.05).

Conclusions

Our results suggest a high rate of under-reporting of pertussis in Jiangsu Province both pre- and post-COVID-19 pandemic, and there are a large number of adults of childbearing age who are susceptible to pertussis. It seems imperative that vaccination of adolescents and adults should be considered for inclusion in vaccination programs.

The effectiveness of PCR-RT method for etiological diagnosis of atypical forms of whooping cough

The aim of the study was to evaluate the effectiveness of the PCR-RТ method using the PCR-RТ-IS test system for the etiological diagnosis of whooping cough in the examination of patients with infectious respiratory pathology with prolonged cough and in contact persons. 113 children aged from 1 month to 17 years, 11 months and 29 days, and 146 contact family members were examined. Regardless of the initial diagnosis, all children were examined for whooping cough by bacteriological, molecular genetic and serological methods. For molecular genetic diagnostics a commercial kit and PCR-RT-IS test-system developed at the Gamaleya Research Center were used. The contact persons were examined by the bacteriological method and using the PCR-RT-IS test-system. During the initial examination the diagnoses «Acute respiratory viral infectious», «Acute rhinopharyngitis», «Acute laryngotracheitis», «Acute bronchitis», «Pneumonia» were established. The severity of cough in contact persons was different – from a typical spastic «whooping cough» to complete absence of cough. By using the PCR-RT-IS test-system we developed, the DNA of pertussis pathogen was detected in groups of patients with «Acute rhinopharyngitis» in 34.4% of cases, «Acute laryngotracheitis» – in 64.3%, «Acute bronchitis» – in 69%, with a diagnosis of «Pneumonia» – in 33.3% of cases. In a number of cases combined course of whooping cough with respiratory infections (respiratory syncytial virus, rhinovirus and others) was detected. In the examined contact persons the causative agent of pertussis was detected using the PCR-RT-IS test-system in 51,4% of cases.

Clinical evaluation of a new rapid immunochromatographic test for detection of Bordetella pertussis antigen

A more rapid and less complicated test to diagnose pertussis is required in clinical settings. We need to detect Bordetella pertussis, which mainly causes pertussis, as early as possible, because pertussis is more likely to become severe in infants, and people around them can easily become a source of infection due to its strong infectivity. Nevertheless, methods that can detect B. pertussis rapidly and efficiently are lacking. Therefore, we developed a new immunochromatographic antigen kit (ICkit) for the early diagnosis of pertussis. The ICkit detects B. pertussis antigens in a nasopharyngeal swab without equipment and provides the result in about 15 min with a simple procedure. Additionally, a prospective study to evaluate the ICkit was conducted in 11 medical institutions, involving 195 cases with suspected pertussis. Compared with the real-time polymerase chain reaction (rPCR), the sensitivity and specificity of the ICkit were 86.4% (19/22) and 97.1% (168/173), respectively. The ICkit detected the antigen in both children and adults. Furthermore, the ICkit detected the antigen until the 25th day from the onset of cough, when rPCR detected the antigen. Thus, the ICkit demonstrated a high correlation with rPCR and would help diagnose pertussis more rapidly and efficiently.

Childhood pertussis is still here: An Asian city's perspectives

INTRODUCTION

Pertussis, or whooping cough, is a highly contagious respiratory infection that is caused by the bacterium Bordetella pertussis. It is one of the most common causes of death in childhood. It is also a frequent cause of chronic cough in children, adolescents, and adults.

METHODS

Global and Hong Kong perspectives of childhood pertussis were described.

RESULTS

Hong Kong has prided herself in the city's childhood immunization program. There appear to be no major outbreaks of pertussis since the 1960s. Nevertheless, pediatricians may see isolated cases of pertussis or pertussis-like cases from time to time. Occasionally, infants are severely affected with apneas and managed with ventilator supports in the PICU. Outbreaks of the notifiable disease continue to occur despite a reasonable surveillance system and vaccination program in Hong Kong. Vaccination of mothers, adolescents, and adults are efficacious methods to further reduce the risks of pertussis. Macrolides remain efficacious antibiotics especially used early during the infectious phase. Infants with pertussis may require intensive care support and morbidity is high.

CONCLUSIONS

Physicians should be reminded from time to time that outbreaks of pertussis still exist in Hong Kong and in many cities globally.

Burden of whooping cough in China (PertussisChina): study protocol of a prospective, population-based case-control study

INTRODUCTION

Pertussis is one of the top 10 diseases of children under 10 years of age, and the few vaccine-preventable diseases who is on a rise in China in recent years; however, the true burden of pertussis, including age-stratified incidence and risk factors of severe sequelae, are under-recognised. We aim to estimate the health burden of laboratory-confirmed pertussis by age groups, considering the setting of illness onset (ie, in community, outpatient and inpatient), in a Chinese population (~2.23 million in total) at two sites.

METHODS AND ANALYSIS

This paper describes the study design of a 1-year, prospective, age-stratified and population-based case-control study, including site selection, study population, case registry, ascertainment and enrolment, control recruitment, follow-up of case, microbiological methods, data collection, quality control activities and statistical methods used to generate incidence estimates. During June 2021 through May 2022, registry of suspected pertussis cases (namely chronic/persistent cough) will be conducted in several participating hospitals (SHs) at the two sites, which are selected based on Healthcare Utilisation and Attitudes Surveys (HUAS) carried out before study initiation. A case-control study will be conducted in the SHs and we aim to enrol a total of 1000 suspected pertussis cases (ie, all hospital admissions and the first 1-3 outpatient visits each week each hospital) and 2000 frequency matched healthy controls in community. Our primary study outcome, the laboratory-confirmed Bordetella pertussis infection, will be determined by a comprehensive laboratory methods and procedures (ie, culture, PCR and serological tests) in both cases and controls at enrolment and during 60-day's follow-up visits. Finally, data from HUAS (ie, population size), case registry (ie, the total number of suspected pertussis cases) and case-control study (ie, the prevalence or population attributable fraction of Bordetella pertussis) will be combined to calculate incidence and its 95% CI through bootstrap method. Epidemiological analyses will be conducted to determine the risk factors associated with severe sequelae of pertussis.

ETHICS AND DISSEMINATION

This study has been approved by Chinese Centre for Disease Control and Prevention's Institutional Review Board (no. ICDC-202110). Results will be disseminated via academic presentations and publication in peer-reviewed journals, and will provide valuable scientific data and some new insights into the incidence, aetiology and risk factors for severe sequelae of pertussis to academic societies and the public health authorities who is currently struggling and fighting against this burdensome disease worldwide.

Reduced Bordetella pertussis-specific CD4+ T-Cell Responses at Older Age

Pertussis, a human-specific respiratory infectious disease caused by the Gram-negative bacterium Bordetella pertussis (Bp), remains endemic with epidemic years despite high vaccination coverage. Whereas pertussis vaccines and natural infection with Bp confer immune protection, the duration of protection varies and is not lifelong. Recent evidence indicates a considerable underestimation of the pertussis burden among older adults. Whereas the impact of increasing age on Bp-specific humoral immunity has been demonstrated, little is known on immunosenescence of CD4⁺ T-cell responses in the context of Bp. Here, we aimed to address whether increasing age impacts responsiveness of the Bp-specific CD4⁺ T-cells in the memory pool following a clinically symptomatic pertussis infection in whole cell vaccine-primed pediatric and adult cases. Cytokine and proliferative responses and phenotypical profiles of CD4⁺ T cells specific for Bp antigens at an early and late convalescent timepoint were compared. Responses of various Th cytokines, including IFNγ, were significantly lower in older adults at early and late timepoints post diagnosis. In addition, we found lower frequencies of Bp-specific proliferated CD4⁺ T cells in older adults, in the absence of differences in replication profile. Phenotyping of Bp-specific CD4⁺ T cells suggested reduced expression of activation markers rather than increased expression of co-inhibitory markers. Altogether, our findings show that the magnitude and functionality of the Bp-specific memory CD4⁺ T-cell pool decrease at older age. Declined CD4⁺ T-cell responsiveness to Bp is suggested to contribute to the burden of pertussis in older adults.

Epidemiological and clinical characteristics of pertussis in children and their close contacts in households: A cross-sectional survey in Zhejiang Province, China

BACKGROUND

Despite the expanded immunization programs, the "re-emergence of pertussis" has become a global concern in recent years. At present, the prevalence of pertussis in China is seriously underestimated, and the role of close contact on the disease spreading in children remains unclear.

OBJECTIVES

Our study aimed to investigate pertussis's epidemiological and clinical characteristics in children and their close contacts in households, as well as the antimicrobial resistance of Bordetella pertussis (B. pertussis) in Zhejiang Province, China.

METHODS

We have collected the retrospective and prospective data of children who were suspected of pertussis and their close contacts in households from January 1, 2018, to December 31, 2020, in the Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China. Nasopharyngeal swabs were collected and cultured for B. pertussis. Antibiotics susceptibility test was determined by using E-test methods. Clinical information was collected from the medical records systems.

RESULTS

A total of 350 index patients and their 946 family members (close contacts in households) from 350 families were recruited. B. pertussis strains were isolated from 130 (37.1%) index patients and 116 (12.3%) close contacts. 37 index patients had negative culture results for B. pertussis while their close contacts were positive. A higher positive rate was found in female adults than that in male adults (16.3% vs. 5.1%, P < 0.01). The positive rate in index patients from multi-child families was significantly higher than that from one-child families (51.7% vs. 37.7%, P < 0.05). 53.3% of the pertussis patients were under 6 months of age. 98 (75.4%) isolates had MICs ≥ 256 mg/L to erythromycin, azithromycin, and clindamycin, and 127 (97.7%) had MICs < 0.016 mg/L to piperacillin.

CONCLUSION

Infants under 6 months of age are at high risk of pertussis, and close contacts in households are prone to cluster infection. Culture for B. pertussis both in children and their close contacts contributes to improving the diagnosis rate of pertussis in children. Isolates of B. pertussis in China are highly resistant to macrolides.

Duration of protection against Bordetella pertussis infection elicited by whole-cell and acellular vaccine priming in Polish children and adolescents

BACKGROUND

In the context of reported resurgence of pertussis in the last decade, researchers hypothesized that acellular (aP) pertussis vaccines elicit a shorter-lived protection compared to whole-cell (wP) pertussis vaccines. However, in the studies seeking to demonstrate this hypothesis, exposure to each vaccine type was not concurrent, and contradictory epidemiologic modeling questioned its validity. The context of pertussis vaccination history in Poland, with both vaccine types used concurrently in comparable proportions, provided an opportunity to investigate this hypothesis. We sought to compare waning of protection by primary series vaccine type by measuring anti-pertussis toxin antibody concentrations as proxy for recent infection.

MATERIALS AND METHODS

Serological samples from 2,745 children and adolescents aged ≥5 years and <16 years and with completed 5-dose pertussis vaccination series were tested by ELISA for pertussis toxin (PT) antibodies. Participants were stratified by type of priming vaccine (wP or aP). Vaccination timeliness and priming-specific trends in anti-PT antibody levels by time since last vaccine dose were analyzed.

RESULTS

A total of 1,161 (42.5%) children received wP vaccines, and 1,314 (48.1%) received aP vaccines for their primary series and toddler booster. Overall, 53.57% of the subjects received doses 2-4 in a timely manner, while only 41.52% received all 5 doses at the recommended intervals. Using GMCs or seropositivity measures, both priming groups showed a re-increase in anti-PT antibody levels signing infection in recent years from 8 years after the school-entry booster onward. Comparisons did not show any significant differences between the two groups in the timing or intensity of this re-increase.

CONCLUSION

Our results clearly confirm that vaccine-elicited immunity against pertussis wanes among adolescents even after a complete infant, toddler and school-entry vaccination series. The timing and intensity of the waning of protection appear similar with whole-cell as with acellular pertussis vaccines.

The Path to New Pediatric Vaccines against Pertussis

Whooping cough, or pertussis, mostly caused by Bordetella pertussis, is a respiratory disease that affects all age groups, but severe and fatal pertussis occurs almost exclusively in young children. The widespread use of whole-cell and, more recently, of acellular vaccines has substantially reduced the disease incidence. However, it has not been eliminated in any part of the world and has made a worrisome rebound in several areas. Cocoon and maternal immunization have been implemented in several countries but have their intrinsic limitations. To effectively control pertussis, novel vaccines are needed that protect against disease and prevent B. pertussis infection and transmission, which is not the case for current vaccines. Several approaches are contemplated, including alternative administration routes, such as nasal immunization, improvement of acellular vaccines by adding more antigens and T-cell-promoting adjuvants, and the development of novel vaccines, such as outer membrane vesicles and live attenuated vaccines. Among them, only a live attenuated vaccine has so far been assessed for safety and immunogenicity in preclinical models other than mice and is in clinical development. Before any of these vaccines can be used in neonates, extensive safety and immunogenicity assessment in pre-clinical neonatal models and in carefully designed clinical trials is necessary. The aim of this review is to discuss the current pertussis problem, implemented strategies to resolve it, the value of animal models and novel vaccine approaches.

Suppression of mucosal Th17 memory responses by acellular pertussis vaccines enhances nasal Bordetella pertussis carriage

Pertussis has made a spectacular rebound in countries that have switched from whole-cell (wPV) to acellular pertussis vaccines (aPV). Here, we show that, unlike wPV, aPV, while protective against lung colonization by Bordetella pertussis (Bp), did not protect BALB/c mice from nasal colonization, but instead substantially prolonged nasal carriage. aPV prevented the natural induction of nasal interleukin-17 (IL-17)-producing and interferon-γ (IFN-γ)-producing CD103⁺ CD44⁺ CD69⁺ CD4⁺-resident memory T (T_RM) cells. IL-17-deficient, but not IFN-γ-deficient, mice failed to clear nasal Bp, indicating a key role of IL-17⁺ T_RM cells in the control of nasal infection. These cells appeared essential for neutrophil recruitment, crucial for clearance of Bp tightly bound to the nasal epithelium. Transfer of IL-17⁺ T_RM cells from Bp-infected mice to IL-17-deficient mice resulted in neutrophil recruitment and protection against nasal colonization. Thus, aPV may have augmented the Bp reservoir by inhibiting natural T_RM cell induction and neutrophil recruitment, thereby contributing to the pertussis resurgence.

Manufacture of a Stable Lyophilized Formulation of the Live Attenuated Pertussis Vaccine BPZE1

Current pertussis vaccines protect against disease, but not against colonization by and transmission of Bordetella pertussis, whereas natural infection protects against both. The live attenuated vaccine BPZE1 was developed to mimic immunogenicity of natural infection without causing disease, and in preclinical models protected against pertussis disease and B. pertussis colonization after a single nasal administration. Phase 1 clinical studies showed that BPZE1 is safe and immunogenic in humans when administered as a liquid formulation, stored at ≤-70 °C. Although BPZE1 is stable for two years at ≤-70 °C, a lyophilized formulation stored at ≥5 °C is required for commercialization. The development of a BPZE1 drug product, filled and lyophilized directly in vials, showed that post-lyophilization survival of BPZE1 depended on the time of harvest, the lyophilization buffer, the time between harvest and lyophilization, as well as the lyophilization cycle. The animal component-free process, well defined in terms of harvest, processing and lyophilization, resulted in approximately 20% survival post-lyophilization. The resulting lyophilized drug product was stable for at least two years at -20 °C ± 10 °C, 5 °C ± 3 °C and 22.5 °C ± 2.5 °C and maintained its vaccine potency, as evaluated in a murine protection assay. This manufacturing process thus enables further clinical and commercial development of BPZE1.

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 Infections Among Pregnant Women in the United States, 2012–2017

Background

Little is known about pertussis among pregnant women, a population at increased risk for severe morbidity from respiratory infections such as influenza. We used the Centers for Disease Control and Prevention’s Enhanced Pertussis Surveillance (EPS) system to describe pertussis epidemiology among pregnant and nonpregnant women of childbearing age.

Methods

Pertussis cases in women aged 18–44 years with cough onset between 1 January 2012 and 31 December 2017 were identified in 7 EPS states. Surveillance data were collected through patient and provider interviews and immunization registries. Bridged-race, intercensal population data and live birth estimates were used as denominators.

Results

We identified 1582 pertussis cases among women aged 18–44 years; 5.1% (76/1499) of patients with a known pregnancy status were pregnant at cough onset. Of the pregnant patients with complete information, 81.7% (49/60) reported onset during the second or third trimester. The median ages of pregnant and nonpregnant patients were 29.0 and 33.0 years, respectively. Most pregnant and nonpregnant patients were White (78.3% vs. 86.4%, respectively; P = .09) and non-Hispanic (72.6% vs. 77.3%, respectively; P = .35). The average annual incidence of pertussis was 7.7/100000 among pregnancy women and 7/3/100000 among nonpregnant women. Compared to nonpregnant patients, more pregnant patients reported whoop (41.9% vs. 31.3%, respectively), posttussive vomiting (58.1% vs. 47.9%, respectively), and apnea (37.3% vs. 29.0%, respectively); however, these differences were not statistically significant (P values &gt; .05 for all). A similar proportion of pregnant and nonpregnant patients reported ever having received Tdap (tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine; 31.6% vs. 32.7%, respectively; P = .84).

Conclusions

Our analysis suggests that incidence of pertussis and clinical characteristics of disease are similar among pregnant and nonpregnant women. Continued monitoring is important to further define pertussis epidemiology in pregnant women.

Cleft Nucleus Lymphocytosis in Young Infants with Pertussis

This study aims to assess whether the cleft nucleus lymphocytosis could be an early promising clue for the diagnosis of pertussis in young infants. Pertussis (whooping cough) is a severe respiratory disease mainly caused by Bordetella pertussis infection and is characterized by a significant rise in the number of leukocyte and lymphocyte in infants and young children. In this study, the Bordetella pertussis DNA was detected from samples of pharyngeal swab by PCR assay. Levels of serum specific IgM against other respiratory pathogens were detected by Enzyme-linked immunosorbent assay (ELISA) assay. The routine blood test including numbers of leukocytes, lymphocytes, and platelets etc. were tested by automatic hemocyte analyzer (Sysemx XN1000). Besides, the morphology of leucocytes was observed in peripheral blood smear with microscope by Wright-Giemsa stain. Three cases of pertussis with cleft nucleus lymphocytes in young infants were discussed in in the neonatal/pediatric intensive care unit in our hospital. Leukocytosis characterized by lymphocytes, as well as thrombocytosis were observed in all patients. Our results demonstrated that cleft nucleus lymphocytosis accompanied with leukocytosis and lymphocytes would be potent assistant indicators for the early diagnosis of pertussis in young children.

An Investigation of Japanese Neonatal and Maternal Antibody Status against Pertussis

To clarify the pertussis immune status of the Japanese population, we investigated levels of serum pertussis toxin (PT)-specific immunoglobulin G (IgG) antibody in infants and mothers between April 2016 and March 2018. A total of 206 infants (n = 22, < 32 weeks of gestational age [wGA]; n = 70, 32-36 wGA; n = 114, ≥ 37 wGA) and 170 mothers were enrolled. The maternal seroprevalence and antibody geometric mean titer (GMT) were 52.4% and 10.7 EU/mL, respectively. The antibody GMT, seroprevalence, and mean ratio of infant to maternal antibody titers of infants at < 32 wGA were 3.2 EU/mL, 13.6%, and 42.5%, respectively, and were significantly lower than those of infants at 32-36 wGA (9.7 EU/mL, 54.3%, and 110.2%) and infants at ≥ 37 wGA (12.1 EU/mL, 57.9%, and 112.6%). Of the 21 infants who underwent a second examination, five were positive in the first examination. Of those five, the GMT for PT had decreased by an average of 52.6% at 4.3- week intervals. In the second examination, two infants were seropositive. Approximately half of the mothers and infants were negative for anti-PT antibody. Thus, new vaccination strategies, such as the vaccination of pregnant women, are needed to prevent pertussis infection in early infancy.

Acellular Pertussis Vaccine Components: Today and Tomorrow

Pertussis is a highly communicable acute respiratory infection caused by Bordetella pertussis. Immunity is not lifelong after natural infection or vaccination. Pertussis outbreaks occur cyclically worldwide and effective vaccination strategies are needed to control disease. Whole-cell pertussis (wP) vaccines became available in the 1940s but have been replaced in many countries with acellular pertussis (aP) vaccines. This review summarizes disease epidemiology before and after the introduction of wP and aP vaccines, discusses the rationale and clinical implications for antigen inclusion in aP vaccines, and provides an overview of novel vaccine strategies aimed at better combating pertussis in the future.

Development and Standardization of a High-Throughput Bordetella pertussis Growth-Inhibition Assay

Bordetella pertussis, the main causative agent of whooping cough, is a reemerging pathogen, and recent vaccine-resistant strain outbreaks and emergence of macrolides-resistant strains in China raised new concerns for control of the disease. New vaccines and potentially new antibiotics are thus needed. B. pertussis is tedious to culture and requires several days of growth to count isolated colonies on agar-based media, making large-scale screening of new anti-B. pertussis compounds or functional evaluation of large sample sizes of immune sera difficult. Here, we developed a scalable, rapid, high-throughput luminescence-based Bordetella growth inhibition assay (BGIA) to quantify surviving bacteria after treatment with anti-B. pertussis compounds. A strong correlation between luminescence and colony-forming units (r² = 0.9345, p < 0.0001) was found and the BGIA showed high sensitivity and reproducibility. We demonstrate here that the BGIA can be used to quantify resistance of B. pertussis to antibiotics, sensitivity to complement and to human serum in an easy-to-operate and fast manner. We have optimized the assay and tested the effects of different B. pertussis strains and growth conditions on serum and complement sensitivity. We also uncovered complement-independent antibody-mediated inhibition of B. pertussis growth. The BGIA can thus effectively be implemented for large-scale serum studies to further investigate anti-B. pertussis immune responses at a functional level, as well as for screening of B. pertussis strains for their resistance to antibiotics or complement, and for high-throughput screening of novel anti-B. pertussis compounds.

Clinical Findings and Management of Pertussis

Pertussis is an endemic highly infectious vaccine-preventable disease. The disease is a major cause of childhood morbidity and mortality. In the most recent years, the re-emergence of pertussis occurred, and many efforts were done to identify the possible causes. Certainly, more effective laboratory methods have a role in making the diagnosis easier. However, sub-optimal efficacy of available vaccines as well as their limited duration of protection could explain the resurgence of the disease. Many forms and clinical features of the disease, ranging from the most classical to atypical and very nuanced forms, have been reported. There are many aspects that influence the clinical features of the pathology, such as a previous immunization or infection, patient's age, gender and antibiotic treatment. A prompt suspect and a rapid diagnosis of pertussis is fundamental for an appropriate clinical management and for preventing pertussis complications, especially in children. However, under a clinical point of view, pertussis is often difficult to be diagnosed. A prompt treatment may decrease the duration and severity of cough; the cornerstone drugs are the macrolides. Although prompt diagnosis and effective therapy are important for pertussis control, only with a broad vaccination coverage will be possible to reduce circulation of Bordetella pertussis.

Immunological and Clinical Benefits of Maternal Immunization Against Pertussis: A Systematic Review

Infants are vulnerable to pertussis infection particularly before initiation of pertussis vaccination. Maternal pertussis vaccination during pregnancy has been introduced in a number of countries in order to confer on young infants indirect protection from the disease through transplacental transfer of maternal antibodies. We reviewed the evidence on the immunogenicity and efficacy of maternal pertussis vaccination during pregnancy. A systematic search of PubMed/MEDLINE, EMBASE, Scopus, Cochrane Database of Systematic Reviews, ProQuest, and Science Direct was undertaken to identify studies published between January 1995 and December 2018. This review was not specific to any particular pertussis vaccine but included applicable data on available pertussis vaccines administered to pregnant women. The search identified 40 publications for inclusion in this review. Vaccination during pregnancy elicited robust maternal immune responses against all vaccine antigens and resulted in high placental transfer of pertussis antibodies to the infant that persisted well beyond delivery. Vaccination during the second or early third trimesters was considered ideal for antibody quantity and functionality. Although blunting of immune responses to some antigens in the primary immunization series was documented in neonates born to women vaccinated during pregnancy, there was no apparent adverse effect on vaccine efficacy. Multiple studies conducted in diverse settings have confirmed the effectiveness of maternal pertussis vaccination during pregnancy in preventing pertussis in infants prior to receipt of their first primary vaccine dose and beyond. These findings collectively underscore the value of maternal pertussis vaccination during pregnancy in protecting vulnerable infants too young to be vaccinated.Funding Sanofi Pasteur.Plain Language Summary Plain language summary available for this article.

Age-related differences in antibody avidities to pertussis toxin and filamentous hemagglutinin in a healthy Japanese population

To gain insights into the current Japanese pertussis immunization schedule, we examined the distributions of antibody titers and avidities to pertussis toxin (PT) and filamentous hemagglutinin (FHA) in 460 Japanese healthy subjects (aged 1-60 years) based on age category. Our avidity enzyme-linked immunosorbent assays revealed that young children aged 1-2 years, which corresponded to ages after receiving primary and/or booster pertussis vaccinations, had relatively high-avidity anti-PT IgG (mean avidity index [AI], 40.5%) compared with other age groups (AI, 26.5-31.9%); however, they had relatively low-avidity anti-FHA IgG (AI, 41.8%). In contrast, children aged 3-6 years had both low-avidity anti-PT IgG (AI, 26.5%) and low-avidity anti-FHA IgG (AI, 40.4%). A significant age-related difference in anti-PT IgG avidity was observed between children aged 1-2 years and 3-6 years (P < 0.05); however, the difference in anti-FHA IgG avidity was not significant. The anti-PT IgG avidity was positively correlated with the antibody titer, especially among children aged 1-15 years (r_s = 0.508-0.685; P < 0.01), indicating that the avidity of vaccine-induced anti-PT IgG decreases with decreasing IgG antibody titer to PT. Our findings strongly suggest that vaccine-induced anti-PT IgG avidity rapidly wanes after vaccination, but this is not observed for anti-FHA IgG avidity. Because children aged 3-6 years have both low-quantity and low-quality antibodies against PT, an additional booster vaccination with acellular pertussis vaccines is required for such children in Japan.

[Epidemiological and clinical features of vaccine-preventable diseases in vaccine era]

In countries and regions with high vaccination coverage, several vaccine-preventable diseases have been resurged in recent years, such as measles, varicella, pertussis and mumps. Some studies have found that the clinical manifestation and epidemiological characteristics of these diseases were different from those in pre-vaccine era. This article reviewed the clinical and epidemiological features of vaccine-preventable diseases before and after wide immunization implementation, focusing on the situation in China, in order to attract the attention of clinicians, raise awareness, strengthen prevention and control, and promote in-depth research for these diseases.

Acute Bronchitis Caused by Bordetella Pertussis Possibly Co-Infected with Mycoplasma Pneumoniae

BACKGROUND Mycoplasma pneumoniae and Bordetella pertussis are among the causative pathogens of human acute bronchitis, which usually has mild symptoms. However, if there is a co-infection, the symptoms often can be prolonged and occasionally can lead to severe respiratory complications. CASE REPORT A 49-year-old Japanese female, who had not been vaccinated for B. pertussis, developed a persistent productive cough which became vigorous, and occasionally caused difficulty breathing and vomiting. Since serum IgM to M. pneumoniae was positive and IgG to B. pertussis was significantly elevated, and there were no findings of pneumonia on a chest x-ray film, we made a diagnosis of acute bronchitis caused by B. pertussis with possible co-infection with M. pneumoniae. The use of garenoxacin, a quinolone derivative, failed to work; however, a macrolide antibiotic clarithromycin dramatically improved her symptoms shortly after its administration. CONCLUSIONS In this patient case, because of the lymphocyte-stimulatory nature of M. pneumoniae and B. pertussis, an increased immunological response was likely to be involved in the pathogenesis of the symptoms. The immunosuppressive effect of clarithromycin was considered to repress the increased lymphocyte activity, facilitating the remission of the disease.

The Role of Mucosal Immunity in Pertussis

Pertussis or whooping cough, mainly caused by Bordetella pertussis, is a severe respiratory disease that can affect all age groups but is most severe and can be life-threatening in young children. Vaccines against this disease are widely available since the 1950s. Despite high global vaccination coverage, the disease is not under control in any country, and its incidence is even increasing in several parts of the world. Epidemiological and experimental evidence has shown that the vaccines fail to prevent B. pertussis infection and transmission, although they are very effective in preventing disease. Given the high infection rate of B. pertussis, effective control of the disease likely requires prevention of infection and transmission in addition to protection against disease. With rare exceptions B. pertussis infections are restricted to the airways and do not usually disseminate beyond the respiratory epithelium. Therefore, protection at the level of the respiratory mucosa may be helpful for an improved control of pertussis. Yet, compared to systemic responses, mucosal immune responses have attracted relatively little attention in the context of pertussis vaccine development. In this review we summarize the available literature on the role of mucosal immunity in the prevention of B. pertussis infection. In contrast to vaccination, natural infection in humans and experimental infections in animals induce strong secretory IgA responses in the naso-pharynx and in the lungs. Several studies have shown that secretory IgA may be instrumental in the control of B. pertussis infection. Furthermore, studies in mouse models have revealed that B. pertussis infection, but not immunization with current acellular pertussis vaccines induces resident memory T cells, which may also contribute to protection against colonization by B. pertussis. As these resident memory T cells are long lived, vaccines that are able to induce them should provide long-lasting immunity. As of today, only one vaccine designed to induce potent mucosal immunity is in clinical development. This vaccine is a live attenuated B. pertussis strain delivered nasally in order to mimic the natural route of infection. Due to its ability to induce mucosal immunity it is expected that this approach will contribute to improved control of pertussis.

Acute exacerbation of idiopathic pulmonary fibrosis induced by pertussis: the first case report

BACKGROUND

Acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) is a severe condition with limited treatment strategies. Although respiratory infection is a major cause of AE-IPF, no reports have indicated pertussis infection as a cause. Here we report two cases of pertussis infection-induced AE-IPF.

CASE PRESENTATION

Both patients presented with a chief complaint of acute respiratory distress and were previously diagnosed with idiopathic pulmonary fibrosis (IPF). Neither patient had received any pertussis vaccination since adolescence. Both patients were diagnosed with AE-IPF accompanying acute pertussis infection based on chest computed tomography and serum pertussis toxin antibody > 100 EU/mL. Both patients were treated with macrolide antibiotics and systemic corticosteroids. Both patients were able to be discharged and return home.

CONCLUSIONS

The presence of pertussis infection in AE-IPF can present a diagnostic challenge, as coughing accompanying pertussis may be difficult to distinguish from IPF-associated coughing. Pertussis infection should be assayed in AE-IPF patients. Since pertussis can be prevented with vaccination and is expected to be affected by antibiotics, consideration of pertussis infection as a causative virulent factor of AE-IPF may be important for management of subjects with IPF.

Superior B. pertussis Specific CD4+ T-Cell Immunity Imprinted by Natural Infection

Pertussis remains endemic in vaccinated populations due to waning of vaccine-induced immunity and insufficient interruption of transmission. Correlates of long-term protection against whooping cough remain elusive but increasing evidence from experimental models indicates that the priming of particular lineages of B. pertussis (Bp) specific CD4+ T cells is essential to control bacterial load. Critical hallmarks of these protective CD4+ T cell lineages in animals are suggested to be their differentiation profile as Th1 and Th17 cells and their tissue residency. These features seem optimally primed by previous infection but insufficiently or only partially by current vaccines. In this review, evidence is sought indicating whether infection also drives such superior Bp specific CD4+ T cell lineages in humans. We highlight key features of effector immunity downstream of Th1 and Th17 cell cytokines that explain clearing of primary Bp infections in naïve hosts, and effective prevention of infection in convalescent hosts during secondary challenge. Outstanding questions are put forward that need answers before correlates of human Bp infection-primed CD4+ T cell immunity can be used as benchmark for the development of improved pertussis vaccines.

Pertussis: The Whooping Cough

Bordetella pertussis can cause serious and potentially fatal complications, especially in very young infants. Early diagnosis and treatment of pertussis with a macrolide antibiotic, such as azithromycin, before the paroxysmal stage of disease can help mitigate complications and reduce the spread of this highly contagious disease.

IL-17-dependent SIgA-mediated protection against nasal Bordetella pertussis infection by live attenuated BPZE1 vaccine

BPZE1 is a live attenuated Bordetella pertussis vaccine for nasal administration to mimic the natural route of infection. Here, we studied the mechanism of BPZE1-induced immunity in the murine nasal cavity in contrast to acellular vaccine (aPV), although both vaccines protected against lung colonization. Transfer of splenocytes or serum from BPZE1-vaccinated or aPV-vaccinated mice protected naïve mice against lung colonization but not against nasal colonization. However, transfer of nasal washes from BPZE1-vaccinated mice resulted in protection against nasal colonization, which was lost in IgA-deficient or poly-Ig receptor-deficient mice, indicating that it depends on secretory IgA (SIgA) induction induced in the nose. BPZE1-induced protection against nasal colonization was long-lived despite the relatively rapid decay of SIgA, indicating a potent BPZE1-induced local memory response, likely due to CD4⁺ tissue-resident memory T cells induced in the nose by BPZE1. These cells produced interleukin-17 (IL-17), known to be important for SIgA secretion. Furthermore, BPZE1 failed to protect Il17^-/- mice against nasal colonization by B. pertussis and induced only background levels of nasal SIgA. Thus, our results show important differences in the protective mechanism between the upper and the lower murine respiratory tract and demonstrate an IL-17-dependent SIgA-mediated mechanism of BPZE1-induced protection against B. pertussis nasopharyngeal colonization.

Construction and evaluation of Bordetella pertussis live attenuated vaccine strain BPZE1 producing Fim3

Pertussis or whooping cough is currently the most prevalent vaccine-preventable childhood disease despite >85% global vaccination coverage. In recent years incidence has greatly increased in several high-income countries that have switched from the first-generation, whole-cell vaccine to the newer acellular vaccines, calling for improved vaccination strategies with better vaccines. We have developed a live attenuated pertussis vaccine candidate, called BPZE1, which is currently in clinical development. Unlike other pertussis vaccines, BPZE1 has been shown to provide strong protection against infection by the causative agent of pertussis, Bordetella pertussis, in non-human primates. BPZE1 is a derivative of the B. pertussis strain Tohama I, which produces serotype 2 (Fim2) but not serotype 3 fimbriae (Fim3). As immune responses to fimbriae are likely to contribute to protection, we constructed a BPZE1 derivative, called BPZE1f3, that produces both serotypes of fimbriae. Whereas nasal vaccination of mice with BPZE1 induced antibodies to Fim2 but not to Fim3, vaccination with BPZE1f3 elicited antibodies to both Fim2 and Fim3 at approximately the same level. In mice, both BPZE1 and BPZE1f3 provided equal levels of protection against clinical isolates that either produce Fim2 alone, both Fim2 and Fim3, or no fimbriae. However, vaccination with BPZE1f3 provided significantly stronger protection against Fim3-only producing B. pertussis than vaccination with BPZE1, indicating that immune responses to fimbriae contribute to serotype-specific protection against B. pertussis infection.

What Is Wrong with Pertussis Vaccine Immunity? The Problem of Waning Effectiveness of Pertussis Vaccines

Pertussis is resurgent in some countries, particularly those in which children receive acellular pertussis (aP) vaccines in early infancy and boosters later in life. Immunologic studies show that, whereas whole-cell pertussis (wP) vaccines orient the immune system toward Th1/Th17 responses, acellular pertussis vaccines orient toward Th1/Th2 responses. Although aP vaccines do provide protection during the first years of life, the change in T-cell priming results in waning effectiveness of aP as early as 2-3 years post-boosters. Although other factors, such as increased virulence of pertussis strains, better diagnosis, and better surveillance may play a role, the increase in pertussis appears to be the result of waning immunity. In addition, studies in baboon models, requiring confirmation in humans, show that aP is less able to prevent nasopharyngeal colonization of Bordetella pertussis than wP or natural infection.

Pertussis Reinfection in an Adult: A Cause of Persistent Cough Not to Be Ignored

Pertussis is traditionally considered as a disease of the childhood; however, accumulating evidence suggests a stable increase of its incidence among adults and adolescents, during the last decades. Despite the fact that reinfection after natural disease or vaccination is not uncommon, the index of clinical suspicion of pertussis diagnosis in adults remains low. In this article, we report a case of pertussis reinfection 30 years after natural infection, which was complicated by pneumonia, and we discuss our diagnostic and therapeutic approach, aiming to raise clinicians' degree of suspicion regarding pertussis diagnosis in adults. Prompt recognition and appropriate therapy of adult patients can result in the effective control of the symptoms, prevention of severe complications, and spread of the infection to children; thus, they are of great clinical and public health importance.

A high seroprevalence of antibodies to pertussis toxin among Japanese adults: Qualitative and quantitative analyses

In 2013, national serosurveillance detected a high seroprevalence of antibodies to pertussis toxin (PT) from Bordetella pertussis among Japanese adults. Thus, we aimed to determine the cause(s) of this high seroprevalence, and analyzed the titers of antibodies to PT and filamentous hemagglutinin (FHA) among adults (35-44 years old), young children (4-7 years old), and older children (10-14 years old). Our quantitative analyses revealed that adults had higher seroprevalences of anti-PT IgG and PT-neutralizing antibodies, and similar titers of anti-FHA IgG, compared to the young and older children. Positive correlations were observed between the titers of PT-neutralizing antibodies and anti-PT IgG in all age groups (rs values of 0.326-0.522), although the correlation tended to decrease with age. The ratio of PT-neutralizing antibodies to anti-PT IgG was significantly different when we compared the serum and purified IgG fractions among adults (p = 0.016), although this result was not observed among young and older children. Thus, it appears that some adults had non-IgG immunoglobulins to PT. Our analyses also revealed that adults had high-avidity anti-PT IgG (avidity index: 63.5%, similar results were observed among the children); however, the adults had lower-avidity anti-FHA IgG (37.9%, p < 0.05). It is possible that low-avidity anti-FHA IgG is related to infection with other respiratory pathogens (e.g., Bordetella parapertussis, Haemophilus influenzae, or Mycoplasma pneumoniae), which produces antibodies to FHA-like proteins. Our observations suggest that these adults had been infected with B. pertussis and other pathogen(s) during their adulthood.

Seroepidemiology of whooping cough in the Czech Republic: estimates of incidence of infection in adults

OBJECTIVES

Despite widespread vaccination programmes, pertussis remains a significant health burden in many countries. Low awareness of the disease, the high rate of asymptomatic cases in adults and difficulties with diagnosis could explain the under-reporting of pertussis. The lack of data on actual incidence constitutes an obstacle for public health authorities for the implementation of a vaccination strategy against pertussis in adults. The aim of this study was to evaluate the seroprevalence of antibodies against Bordetella pertussis infection in adults and to estimate the actual incidence of the disease compared with the reported incidence.

STUDY DESIGN

Prospective, multicentre seroprevalence study.

METHODS

The study was conducted in 2000 adult subjects aged ≥18 years who had not received pertussis vaccination within the last 5 years. All enrolled subjects provided a blood sample for serum testing of IgG antibodies against pertussis toxin, performed by enzyme-linked immunosorbent assay, to indicate if they had an acute infection or if they had been infected with pertussis within the last 12 months or earlier. Results were validated in accordance with the guidelines of the European Sero-epidemiology Network 2 and were expressed in ESEN units/ml.

RESULTS

A positive concentration of anti-pertussis toxin antibodies, indicating previous pertussis infection, was demonstrated in 39.9% (n = 799) of all study subjects, and 0.40% (n = 8) of subjects had a concentration suggestive of a recent infection (within the last 12 months). The highest antibody seroprevalence was observed in subjects aged 18-29 years (1.46%). No cases of acute infection were detected.

CONCLUSIONS

During the study period, the reported incidence of pertussis in the adult population was 0.84/100,000 inhabitants. Based on the seroprevalence results from this study, it is estimated that the actual incidence of pertussis could be as much as 699/100,000 inhabitants. The actual incidence of pertussis in adults in the Czech Republic could therefore be at least 200-fold higher than the reported incidence. These findings support the need for pertussis vaccination in the adult population.

Clinical Characteristics of Pertussis-Associated Cough in Adults and Children: A Diagnostic Systematic Review and Meta-Analysis

BACKGROUND

Pertussis (whooping cough) is a highly infective cause of cough that causes significant morbidity and mortality. Existing case definitions include paroxysmal cough, whooping, and posttussive vomiting, but diagnosis can be difficult. We determined the diagnostic accuracy of clinical characteristics of pertussis-associated cough.

METHODS

We systematically searched CINAHL, Embase, Medline, and SCI-EXPANDED/CPCI-S up to June 2016. Eligible studies compared clinical characteristics in those positive and negative for Bordetella pertussis infection, confirmed by laboratory investigations. Two authors independently completed screening, data extraction, and quality and bias assessments. For each characteristic, RevMan was used to produce descriptive forest plots. The bivariate meta-analysis method was used to generate pooled estimates of sensitivity and specificity.

RESULTS

Of 1,969 identified papers, 53 were included. Forty-one clinical characteristics were assessed for diagnostic accuracy. In adult patients, paroxysmal cough and absence of fever have a high sensitivity (93.2% [CI, 83.2-97.4] and 81.8% [CI, 72.2-88.7], respectively) and low specificity (20.6% [CI, 14.7-28.1] and 18.8% [CI, 8.1-37.9]), whereas posttussive vomiting and whooping have low sensitivity (32.5% [CI, 24.5-41.6] and 29.8% [CI, 8.0-45.2]) and high specificity (77.7% [CI, 73.1-81.7] and 79.5% [CI, 69.4-86.9]). Posttussive vomiting in children is moderately sensitive (60.0% [CI, 40.3-77.0]) and specific (66.0% [CI, 52.5-77.3]).

CONCLUSIONS

In adult patients, the presence of whooping or posttussive vomiting should rule in a possible diagnosis of pertussis, whereas the lack of a paroxysmal cough or the presence of fever should rule it out. In children, posttussive vomiting is much less helpful as a clinical diagnostic test.

Assessment of safety and efficacy against Bordetella pertussis of a new tetanus-reduced dose diphtheria-acellular pertussis vaccine in a murine model

BACKGROUND

Tetanus-reduced dose diphtheria-acellular pertussis (Tdap) vaccination during adolescence was introduced in response to the resurgence of pertussis in various countries. A new Tdap vaccine was manufactured in Korea as a countermeasure against a predicted Tdap vaccine shortage. This study was performed to evaluate the immunogenicity, safety, and protection efficacy against Bordetella pertussis of the new Tdap vaccine in a murine model.

METHODS

Four-week-old BABL/c mice were used for assessment of immunogenicity and protection efficacy. A single dose of primary diphtheria-tetanus-acellular pertussis (DTaP) vaccine was administered, followed by a single dose of Tdap booster vaccine after a 12-week interval. Anti-pertussis toxin (PT), anti-filamentous hemagglutinin (FHA), and anti-pertactin (PRN) IgG titers were measured before primary vaccination, and before and after booster vaccination. An intranasal challenge test was performed after booster vaccination to determine protection efficacy. To assess safety, mouse weight gain test and leukocytosis promotion test were performed using 4-week-old ddY female mice.

RESULTS

Anti-PT and anti-FHA IgG titers after booster vaccination were significantly higher than those before booster vaccination with either the new vaccine or a commercially available Tdap vaccine (P = 0.01 for all occasions). After booster vaccination, no significant difference was observed between the two vaccines in antibody titers against pertussis antigens (P = 0.53 for anti-PT IgG, P = 0.91 for anti-FHA IgG, P = 0.39 for anti-PRN IgG). In the intranasal challenge test, inoculated B. pertussis was eradicated 7 days after infection. On days 4 and 7 after infection, colony counts of B. pertussis were not significantly different between the new and positive control vaccine groups (P = 1.00). Mean body weight changes and leukocyte counts of the new vaccine, positive control, and negative control groups were not significantly different 7 days after vaccination (P = 0.87 and P = 0.37, respectively). All leukocyte counts in the new vaccine group were within a mean ± 3 standard deviations range.

CONCLUSIONS

A murine model involving a single dose primary DTaP vaccination followed by a single dose Tdap booster vaccination can be used for non-clinical studies of Tdap vaccines. The new Tdap vaccine manufactured in Korea exhibited comparable immunogenicity, protection efficacy, and safety with a commercially available Tdap vaccine.

Lack of Pertussis Protective Antibodies in Healthcare Providers Taking Care of Neonates and Infants in a Children's Hospital

Contact tracing and seroepidemiologic studies were done after a premature baby contracted pertussis in a children's hospital. No infection source was confirmed. Four (3.5%) healthcare providers were positive for anti-pertussis IgM, while only 23% (26/113) were positive for IgG in a following survey. Pertussis vaccination for healthcare providers is needed.

Impact of age and vaccination history on long-term serological responses after symptomatic B. pertussis infection, a high dimensional data analysis

Capturing the complexity and waning patterns of co-occurring immunoglobulin (Ig) responses after clinical B. pertussis infection may help understand how the human host gradually loses protection against whooping cough. We applied bi-exponential modelling to characterise and compare B. pertussis specific serological dynamics in a comprehensive database of IgG, IgG subclass and IgA responses to Ptx, FHA, Prn, Fim2/3 and OMV antigens of (ex-) symptomatic pertussis cases across all age groups. The decay model revealed that antigen type and age group were major factors determining differences in levels and kinetics of Ig (sub) classes. IgG-Ptx waned fastest in all age groups, while IgA to Ptx, FHA, Prn and Fim2/3 decreased fast in the younger but remained high in older (ex-) cases, indicating an age-effect. While IgG1 was the main IgG subclass in response to most antigens, IgG2 and IgG3 dominated the anti-OMV response. Moreover, vaccination history plays an important role in post-infection Ig responses, demonstrated by low responsiveness to Fim2/3 in unvaccinated elderly and by elevated IgG4 responses to multiple antigens only in children primed with acellular pertussis vaccine (aP). This work highlights the complexity of the immune response to this re-emerging pathogen and factors determining its Ig quantity and quality.

Emerging Bordetella pertussis Strains Induce Enhanced Signaling of Human Pattern Recognition Receptors TLR2, NOD2 and Secretion of IL-10 by Dendritic Cells

Vaccines against pertussis have been available for more than 60 years. Nonetheless, this highly contagious disease is reemerging even in countries with high vaccination coverage. Genetic changes of Bordetella pertussis over time have been suggested to contribute to the resurgence of pertussis, as these changes may favor escape from vaccine-induced immunity. Nonetheless, studies on the effects of these bacterial changes on the immune response are limited. Here, we characterize innate immune recognition and activation by a collection of genetically diverse B. pertussis strains isolated from Dutch pertussis patients before and after the introduction of the pertussis vaccines. For this purpose, we used HEK-Blue cells transfected with human pattern recognition receptors TLR2, TLR4, NOD2 and NOD1 as a high throughput system for screening innate immune recognition of more than 90 bacterial strains. Physiologically relevant human monocyte derived dendritic cells (moDC), purified from peripheral blood of healthy donors were also used. Findings indicate that, in addition to inducing TLR2 and TLR4 signaling, all B. pertussis strains activate the NOD-like receptor NOD2 but not NOD1. Furthermore, we observed a significant increase in TLR2 and NOD2, but not TLR4, activation by strains circulating after the introduction of pertussis vaccines. When using moDC, we observed that the recently circulating strains induced increased activation of these cells with a dominant IL-10 production. In addition, we observed an increased expression of surface markers including the regulatory molecule PD-L1. Expression of PD-L1 was decreased upon blocking TLR2. These in vitro findings suggest that emerging B. pertussis strains have evolved to dampen the vaccine-induced inflammatory response, which would benefit survival and transmission of this pathogen. Understanding how this disease has resurged in a highly vaccinated population is crucial for the design of improved vaccines against pertussis.

Impact of a maternal immunization program against pertussis in a developing country

BACKGROUND

Pertussis disease is a growing concern for developing countries. In Argentina, rates of illness and death peaked in 2011. More than 50% of fatalities due to pertussis occurred in infants younger than two months of age, too young for vaccination. In 2012, the government offered immunization with a vaccine containing Tdap to all pregnant women after 20weeks of gestation with the intent of reducing morbidity and mortality in young infants.

METHODS

Maternal acellular pertussis vaccine impact on reducing infant disease burden was estimated based on data from the Argentinean Health Surveillance System. We divided Argentinean states in two groups experiencing high (>50) and low (⩽50) Tdap vaccine coverage and compared these two groups using a Bayesian structural time-series model. Low coverage regions were used as a control group, and the time series were compared before and after the implementation of the Tdap program.

FINDINGS

We observed a relative reduction of 51% (95% CI [-67%, -35%]; p=0.001) in pertussis cases in high coverage states in comparison with the low coverage areas. Analysis of infants between two and six months showed a 44% (95% CI [-66%, -24%]; p=0.001) reduction in illness. Number of deaths was highest in 2011 with 76 fatalities, for an incidence rate of 2.9 per 100,000. Comparing with 2011, rates decreased by 87% to 10 subjects, or 0.9 per 100,000 in 2013.

INTERPRETATION

We show an age-dependent protective effect of maternal Tdap immunization in a developing country for infants younger than six months.

Live pertussis vaccines: will they protect against carriage and spread of pertussis?

Pertussis is a severe respiratory disease that can be fatal in young infants. Its main aetiological agent is the Gram-negative micro-organism Bordetella pertussis. Vaccines against the disease have been in use since the 1950s, and global vaccination coverage has now reached more than 85%. Nevertheless, the disease has not been controlled in any country, and has even made a spectacular come-back in the industrialized world, where the first-generation whole-cell vaccines have been replaced by the more recent, less reactogenic, acellular vaccines. Several hypotheses have been proposed to explain these observations, including the fast waning of acellular vaccine-induced protection. However, recent mathematical modelling studies have indicated that asymptomatic transmission of B. pertussis may be the main reason for the current resurgence of pertussis. Recent studies in non-human primates have shown that neither whole-cell, nor acellular vaccines prevent infection and transmission of B. pertussis, in contrast to prior exposure. New vaccines that can be applied nasally to mimic natural infection without causing disease may therefore be useful for long-term control of pertussis. Several vaccine candidates have been proposed, the most advanced of which is the genetically attenuated B. pertussis strain BPZE1. This vaccine candidate has successfully completed a first-in-man phase I trial and was shown to be safe in young male volunteers, able to transiently colonize the nasopharynx and to induce antibody responses to B. pertussis antigens in all colonized individuals. Whether BPZE1 will indeed be useful to ultimately control pertussis obviously needs to be assessed by carefully conducted human efficacy trials.

Pertussis outbreak among patients and healthcare workers in a provincial dialysis facility in Japan

BACKGROUND

Sixteen pertussis cases in haemodialysis patients and healthcare workers were detected in a 25-bed outpatient haemodialysis facility in Japan between October 2013 and April 2014.

AIM

To describe an outbreak of pertussis among patients and healthcare workers, and to identify risk factors for pertussis infection.

METHODS

Sputum cultures, loop-mediated isothermal amplification assays performed on nasopharyngeal swabs to detect respiratory pathogens including Bordetella pertussis, and serum anti-pertussis toxin immunoglobulin G measurements were performed for all haemodialysis patients and healthcare workers. A retrospective case-control study was performed to identify the risk factors for pertussis infection in the clinic.

FINDINGS

Only six of the 16 pertussis patients (37.5%) had respiratory symptoms. Recent exposure to an unmasked individual with a cough was associated with pertussis infection (odds ratio 6.25, P<0.05). The outbreak was terminated successfully after enforcing the use of surgical masks among both patients and healthcare workers.

CONCLUSION

This report demonstrates the risk of pertussis transmission in a haemodialysis facility, and underscores the importance of wearing surgical masks to control a pertussis outbreak.

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.

Feasibility of Azithromycin Prophylaxis During a Pertussis Outbreak Among Healthcare Workers in a University Hospital in Paris

The objective of the present study was to evaluate the feasibility of azithromycin prophylaxis with respect to tolerability and compliance during a pertussis outbreak among healthcare workers in a university hospital ward. Compliance with the prophylaxis regimen was 89%; compliance was 75% from intent-to-treat perspective. The rate of adverse events was 33%. Female sex was associated with reporting of adverse events. Nonstudents and healthcare workers who reported adverse events were less compliant with the prophylaxis regimen.