Seroprevalence of tetanus and pertussis antibodies among health care workers in Wuhu, China

This study aimed to elucidate the seroprevalence of antibodies to tetanus and pertussis among Chinese health care workers. Blood specimens from health care workers were collected during the 2021 annual medical examination at the First People's Hospital of Wuhu. Commercial ELISA kits were employed to quantify serum IgG antibodies against tetanus toxin (anti-TT IgG) and both IgG and IgA antibodies against pertussis toxin (anti-PT IgG, anti-PT IgA). A concentration of anti-TT IgG exceeding 0.1 IU/ml was deemed seroprotective against tetanus, while concentrations of anti-PT IgG ≥ 50 IU/ml or anti-PT IgA ≥ 15 IU/ml were indicative of a prior pertussis infection. The overall seroprotective rate for anti-TT IgG stood at 10.43% (92/882), with the highest seroprotective rate (13.91%) in the 20-29 age group, followed by the 30-39 age group (10.57%), 40-49 age group (5.80%), and 50-59 age group (5.63%). Eighteen (2.04%) of the studied subjects were positive to anti-PT IgG, and the positive rate in 20-39 age group and 40-59 age group was 1.19% (8/673) and 4.78% (10/209), respectively. Thirty (3.40%) subjects displayed anti-PT IgG levels ≥100 IU/ml and/or anti-PT IgA ≥ 15 IU/ml, suggesting a recent pertussis infection within the preceding year. Over half (503/882, 57.03%) had undetectable anti-PT IgG antibodies. The majority of health care workers in China appear susceptible to tetanus and pertussis, and a significant subset has experienced pertussis infection. The implementation of booster vaccinations against these diseases for Chinese health care workers is recommended.

Multivalent mRNA-DTP vaccines are immunogenic and provide protection from Bordetella pertussis challenge in mice

Acellular multivalent vaccines for pertussis (DTaP and Tdap) prevent symptomatic disease and infant mortality, but immunity to Bordetella pertussis infection wanes significantly over time resulting in cyclic epidemics of pertussis. The messenger RNA (mRNA) vaccine platform provides an opportunity to address complex bacterial infections with an adaptable approach providing Th1-biased responses. In this study, immunogenicity and challenge models were used to evaluate the mRNA platform with multivalent vaccine formulations targeting both B. pertussis antigens and diphtheria and tetanus toxoids. Immunization with mRNA formulations were immunogenetic, induced antigen specific antibodies, as well as Th1 T cell responses. Upon challenge with either historical or contemporary B. pertussis strains, 6 and 10 valent mRNA DTP vaccine provided protection equal to that of 1/20th human doses of either DTaP or whole cell pertussis vaccines. mRNA DTP immunized mice were also protected from pertussis toxin challenge as measured by prevention of lymphocytosis and leukocytosis. Collectively these pre-clinical mouse studies illustrate the potential of the mRNA platform for multivalent bacterial pathogen vaccines.

Pertussis outbreak in children hospitalized in Rabat (Morocco)

INTRODUCTION

Cyclical pertussis epidemics primarily affect young infants. This study aims to estimate pertussis prevalence during the ongoing 2023 outbreak at our institution, focusing on affected age groups and clinical presentations.

MATERIEL AND METHODS

This retrospective study includes patients admitted to Rabat University Hospital Center from 1st January 2021 to 30th June 2023. Symptomatic patients underwent Multiplex Respiratory Panel PCR testing for respiratory infections. The analysis included cases where RT-PCR identified Bordetella spp., with data analysed using SPSS 15.0.

RESULTS

Pertussis cases sharply increased from December 2022, constituting 85.4 % of positive samples. Most cases (78.2 %) occurred in infants under 3 months, presenting symptoms such as coughing (94.5 %) and dyspnoea (94.5 %). Pertussis was suspected in 60 % of RT-PCR confirmed cases. B. pertussis DNA was identified in 81.8 % of cases and B. parapertussis DNA in 18.2 % of cases.

CONCLUSION

The study exposes a significant pertussis outbreak affecting predominantly young infants.

Opposing effects of acellular and whole cell pertussis vaccines on Bordetella pertussis biofilm formation, Siglec-F+ neutrophil recruitment and bacterial clearance in mouse nasal tissues

Despite global vaccination, pertussis caused by Bordetella pertussis (Bp) is resurging. Pertussis resurgence is correlated with the switch from whole cell vaccines (wPV) that elicit TH1/TH17 polarized immune responses to acellular pertussis vaccines (aPV) that elicit primarily TH2 polarized immune responses. One explanation for the increased incidence in aPV-immunized individuals is the lack of bacterial clearance from the nose. To understand the host and bacterial mechanisms that contribute to Bp persistence, we evaluated bacterial localization and the immune response in the nasal associated tissues (NT) of naïve and immunized mice following Bp challenge. Bp resided in the NT of unimmunized and aPV-immunized mice as biofilms. In contrast, Bp biofilms were not observed in wPV-immunized mice. Following infection, Siglec-F+ neutrophils, critical for eliminating Bp from the nose, were recruited to the nose at higher levels in wPV immunized mice compared to aPV immunized mice. Consistent with this observation, the neutrophil chemokine CXCL1 was only detected in the NT of wPV immunized mice. Importantly, the bacteria and immune cells were primarily localized within the NT and were not recovered by nasal lavage (NL). Together, our data suggest that the TH2 polarized immune response generated by aPV vaccination facilitates persistence in the NT by impeding the infiltration of immune effectors and the eradication of biofilms In contrast, the TH1/TH17 immune phenotype generated by wPV, recruits Siglec-F+ neutrophils that rapidly eliminate the bacterial burden and prevent biofilm establishment. Thus, our work shows that aPV and wPV have opposing effects on Bp biofilm formation in the respiratory tract and provides a mechanistic explanation for the inability of aPV vaccination to control bacterial numbers in the nose and prevent transmission.

Safety and immunogenicity of SIIPL Tdap, a new tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccine, in healthy subjects 4-65 years of age: A Phase II/III randomized, observer-blinded, active controlled, multicenter clinical study in Germany

BACKGROUND

This study assessed the safety and immunogenicity of a new booster vaccine against tetanus, diphtheria, and pertussis manufactured by Serum Institute of India Pvt. Ltd (SIIPL Tdap).

METHODS

The Phase II/III trial was randomized (2:1), observer blinded and active controlled. Healthy subjects aged 4-65 years received a single dose of either SIIPL Tdap or comparator Tdap vaccine (Boostrix®, GlaxoSmithKline, Belgium), and were followed-up for 30 days. Blood samples for safety and immunogenicity assessments were collected pre-vaccination and on day 30 post-vaccination. The study assessed safety and reactogenicity of SIIPL Tdap compared to the comparator Tdap as well as the co-primary immunogenicity outcomes: (i) seroprotection rates against diphtheria toxoid (DT) and tetanus toxoid (TT) and (ii) the booster response rates against pertussis toxoid (PT), filamentous hemagglutinin (FHA) and pertactin (PRN) 30 days post-vaccination in all study subjects. A margin of -10 % was used for non-inferiority testing. Secondary outcomes included the booster response rates against DT and TT, seropositivity rates against pertussis antigens, and antibody geometric mean concentrations (GMCs) for all vaccine components.

RESULTS

At Day 30 post-vaccination, SIIPL Tdap was assessed as non-inferior to the comparator Tdap in terms of: i) seroprotection rates against DT (94.4 % vs. 94.9 %) and TT (99.9 % vs. 100 %) and ii) pertussis booster response rates (93.8 % vs. 88.4 % anti-PT, 89.7 % vs. 90.9 % anti-FHA and 86.3 % vs. 84.4 % anti-PRN), for SIIPL Tdap versus comparator Tdap, respectively. GMCs for anti-PT and anti-PRN were higher in subjects vaccinated with SIIPL Tdap compared to comparator Tdap. All other secondary outcomes were comparable. The overall frequency of local and systemic solicited AEs was comparable; no treatment related SAEs were reported.

CONCLUSIONS

Booster vaccination with SIIPL Tdap was non-inferior to comparator Tdap with respect to the immunogenicity of the vaccine components and was equally well tolerated. EudraCT number: 2019-002706-46.

The Decay of Pertussis Antibodies in Children Aged 0-14 Years in Jiangsu Province, China

The purpose of this study was to investigate possible influencing factors based on the distribution of the pertussis toxin (PT) and filamentous hemagglutinin (FHA) antibody levels in 0-14-year-old children in Jiangsu Province, China, and to analyze changes in IgG antibody levels after pertussis vaccination in children over time via a restricted cubic spline (RCS)-fitted binary logistic regression model. We collected surveillance data on pertussis through the National Notifiable Disease Reporting System (NNDRS). Serum samples were collected, and PT IgG/FHA IgG antibody levels were determined via an enzyme-linked immunosorbent assay (ELISA). A binary logistic regression model was fitted with an RCS. Peak incidence occurred in children aged 0-1 years from 2007 to 2022, and a second peak emerged in children aged 5 years and older from 2018 onwards which shifted towards older age groups. The geometric mean concentrations (GMC) of the anti-PT IgG antibody and anti-FHA IgG antibody in 1129 patients were 15.13 (13.49-16.76) IU/mL and 22.99 (21.17-24.81) IU/mL, respectively. The seropositivity rates of the anti-PT IgG and anti-FHA IgG antibodies in the group receiving a full vaccination course (four doses) were significantly higher than those of other groups (24.6% vs. 43.3%). The RCS fitting model showed a non-linear relationship between the duration after immunization and the odds ratio (OR) of having PT-IgG and FHA-IgG antibody concentrations ≥20 IU/mL in children with documented immunization histories (1-4 doses) (Poverall < 0. 001; Pnonlinear ≤ 0.001). The children with histories of immunization demonstrated antibody levels that decreased to very low levels around 17 months after the last dose of the vaccine. Therefore, it is recommended that pertussis-containing vaccines be administered as booster immunizations for older children.

Genomic dissection of the microevolution of Australian epidemic Bordetella pertussis

Whooping cough (pertussis) is a highly contagious respiratory disease caused by the bacterium Bordetella pertussis. Despite high vaccine coverage, pertussis has re-emerged in many countries including Australia and caused two large epidemics in Australia since 2007. Here, we undertook a genomic and phylogeographic study of 385 Australian B. pertussis isolates collected from 2008 to 2017. The Australian B. pertussis population was found to be composed of mostly ptxP3 strains carrying different fim3 alleles, with ptxP3-fim3A genotype expanding far more than ptxP3-fim3B. Within the former, there were six co-circulating epidemic lineages (EL1 to EL6). The multiple ELs emerged, expanded, and then declined at different time points over the two epidemics. In population genetics terms, both hard and soft selective sweeps through vaccine selection pressures have determined the population dynamics of Australian B. pertussis. Relative risk estimation suggests that once a new B. pertussis lineage emerged, it was more likely to spread locally within the first 1.5 years. However, after 1.5 years, any new lineage was likely to expand to a wider region. Phylogenetic analysis revealed the expansion of ptxP3 strains was also associated with replacement of the type III secretion system allele bscI1 with bscI3. bscI3 is associated with decreased T3SS secretion and may allow B. pertussis to reduce immune recognition. This study advanced our understanding of the epidemic population structure and spatial and temporal dynamics of B. pertussis in a highly immunized population.

Review of scientific evidence to support recommendations of the full-dose DTaP-IPV vaccination in pre-school age children in Italy

INTRODUCTION

Two vaccine formulations are available to prevent diphtheria, tetanus, pertussis, and poliomyelitis: the pediatric full-dose (DTaP-IPV) and the reduced dose formulation (dTap-IPV). Different immunization schedules are internationally recommended for the pre-school booster dose.

AREAS COVERED

International and Italian recommendations, scientific evidence on immunogenicity and safety of DTaP/dTap vaccines to support the full dose as a pre-school booster and Italian vaccination coverage (VC) up to adolescence.

EXPERT OPINION

The WHO recommends a '3+1' schedule with DTaP vaccine for primary immunization, followed by a pre-school booster with DTaP or dTap vaccine. In Italy, a '2+1' schedule, with no booster in the second year, and a pre-school booster dose are recommended with DTPa-IPV vaccines. Studies showed a non-inferior immunogenicity in dTap vaccinees in pre-school age; nevertheless, the antibody titers were usually greater in children vaccinated with DTaP, while lower frequencies of adverse events were recorded in children receiving dTap. Italian VCs for pre-school and adolescent boosters have not been satisfactory, which further reduced during the COVID-19 period. In Italy, the pre-school booster offers the last chance to receive a full dose of DTaP vaccine, thus, representing the most suitable intervention to provide lasting protection in children.

Long-Term Immunogenicity upon Pertussis Booster Vaccination in Young Adults and Children in Relation to Priming Vaccinations in Infancy

Booster vaccinations for pertussis are advised in many countries during childhood or adulthood. In a phase IV longitudinal interventional study, we assessed long-term immunity following an extra pertussis booster vaccination in children and adults. Children (9 years of age) were primed in infancy with either the Dutch whole cell pertussis (wP) vaccine (n = 49) or acellular pertussis (aP) vaccines (n = 59), and all children received a preschool aP booster. Adults (25–29 years, n = 86) were wP-primed in infancy and did not receive a preschool booster. All were followed-up for approximately 6 years. After the additional booster, antibody responses to pertussis were more heterogeneous but generally higher in adults compared with children, and additional modelling showed that antibody concentrations remained higher for at least a decade. Serologic parameters indicative of recent pertussis infection were more often found in aP-primed children (12%) compared with wP-primed individuals (2%) (p = 0.052). This suggests that the aP booster vaccination in aP-primed children offers less long-term protection against pertussis infection and consequently against transmission. Together, these data show that aP priming in combination with aP boosting may not be sufficient to prevent circulation and transmission, while wP-primed adults may benefit from enhanced long-lasting immunity.

Leveraging serology to titrate immunization program functionality for diphtheria in Madagascar

Diphtheria is a potentially devastating disease whose epidemiology remains poorly described in many settings, including Madagascar. Diphtheria vaccination is delivered in combination with pertussis and tetanus antigens and coverage of this vaccine is often used as a core measure of health system functioning. However, coverage is challenging to estimate due to the difficulty in translating numbers of doses delivered into numbers of children effectively immunised. Serology provides an alternative lens onto immunisation, but is complicated by challenges in discriminating between natural and vaccine-derived seropositivity. Here, we leverage known features of the serological profile of diphtheria to bound expectations for vaccine coverage for diphtheria, and further refine these using serology for pertussis. We measured diphtheria antibody titres in 185 children aged 6–11 months and 362 children aged 8–15 years and analysed them with pertussis antibody titres previously measured for each individual. Levels of diphtheria seronegativity varied among age groups (18.9% of children aged 6–11 months old and 11.3% of children aged 8–15 years old were seronegative) and also among the districts. We also find surprisingly elevated levels of individuals seropositive to diphtheria but not pertussis in the 6–11 month old age group suggesting that vaccination coverage or efficacy of the pertussis component of the DTP vaccine remains low or that natural infection of diphtheria may be playing a significant role in seropositivity in Madagascar.

Structural basis for antibody binding to adenylate cyclase toxin reveals RTX linkers as neutralization-sensitive epitopes

RTX leukotoxins are a diverse family of prokaryotic virulence factors that are secreted by the type 1 secretion system (T1SS) and target leukocytes to subvert host defenses. T1SS substrates all contain a C-terminal RTX domain that mediates recruitment to the T1SS and drives secretion via a Brownian ratchet mechanism. Neutralizing antibodies against the Bordetella pertussis adenylate cyclase toxin, an RTX leukotoxin essential for B. pertussis colonization, have been shown to target the RTX domain and prevent binding to the α_Mβ₂ integrin receptor. Knowledge of the mechanisms by which antibodies bind and neutralize RTX leukotoxins is required to inform structure-based design of bacterial vaccines, however, no structural data are available for antibody binding to any T1SS substrate. Here, we determine the crystal structure of an engineered RTX domain fragment containing the α_Mβ₂-binding site bound to two neutralizing antibodies. Notably, the receptor-blocking antibodies bind to the linker regions of RTX blocks I–III, suggesting they are key neutralization-sensitive sites within the RTX domain and are likely involved in binding the α_Mβ₂ receptor. As the engineered RTX fragment contained these key epitopes, we assessed its immunogenicity in mice and showed that it elicits similar neutralizing antibody titers to the full RTX domain. The results from these studies will support the development of bacterial vaccines targeting RTX leukotoxins, as well as next-generation B. pertussis vaccines.

Diverse bacterial pathogens use the type 1 secretion system (T1SS) to secrete RTX leukotoxins, which target host leukocytes during infection. T1SS substrates all contain a repetitive C-terminal ‘RTX’ domain that adopts a characteristic β-roll fold and is involved in secretion. Notably, The RTX domain of Bordetella pertussis adenylate cyclase toxin (ACT) mediates leukocyte targeting via binding to the α_Mβ₂ integrin receptor, and antibodies that block receptor binding neutralize toxin activity. However, ACT also contains multiple non-neutralizing epitopes, and precise knowledge of the sites targeted by neutralizing antibodies is desirable for vaccine design. Here we determine the crystal structure of an ACT fragment in complex with two neutralizing antibodies and define the key neutralization-sensitive sites within the RTX domain. This first structure of a heterotypic protein–protein interaction formed by an RTX domain suggests the linker regions between β-roll segments engage binding partners.

Outbreaks in Health Care Settings

Outbreaks and pseudo-outbreaks in health care settings are complex and should be evaluated systematically using epidemiologic and molecular tools. Outbreaks result from failures of infection prevention practices, inadequate staffing, and undertrained or overcommitted health care personnel. Contaminated hands, equipment, supplies, water, ventilation systems, and environment may also contribute. Neonatal intensive care, endoscopy, oncology, and transplant units are areas at particular risk. Procedures, such as bronchoscopy and endoscopy, are sources of infection when cleaning and disinfection processes are inadequate. New types of equipment can be introduced and lead to contamination or equipment and medications can be contaminated at the manufacturing source.

Long-term survivors following autologous haematopoetic stem cell transplantation have significant defects in their humoral immunity against vaccine preventable diseases, years on from transplant

Current international guidelines recommend routinely vaccinating haematopoetic stem cell transplant (HSCT) recipients. Despite significant infection-related mortality following autologous HSCT, routine vaccination programmes (RVP) completion is poor. For recovered HSCT recipients, it is uncertain whether catch-up vaccination remains worthwhile years later. To determine potential susceptibility to vaccine preventable infections, we measured antibody titres in 56 patients, a median of 7 years (range 0-29) following autologous HSCT, who had not completed RVP. We found that almost all participants had inadequate titres against diphtheria (98.2%) and pneumococcal infection (100%), and a significant proportion had inadequate titres against measles (34.5%). Of those subsequently vaccinated according to available guidelines, many mounted adequate serological responses. These data suggest a pragmatic catch-up approach for autologous HSCT recipients who have not completed RVP is advisable, with universal vaccination against some pathogens (e.g. Streptococcus pneumoniae and diphtheria) and serologically-guided approaches for others (e.g. measles and varicella zoster virus).

A Call for Caution in Use of Pertussis Vaccine Effectiveness Studies to Estimate Waning Immunity: A Canadian Immunization Research Network Study

BACKGROUND

Vaccine effectiveness (VE) studies provide essential evidence on waning vaccine-derived immunity, a major threat to pertussis control. We evaluated how study design affects estimates by comparing 2 case-control studies conducted in Ontario, Canada.

METHODS

We compared results from a test-negative design (TND) with a frequency-matched design (FMD) case-control study using pertussis cases from 2005-2015. In the first study, we identified test-negative controls from the public health laboratory that diagnosed cases and, in the second, randomly selected controls from patients attending the same physicians that reported cases, frequency matched on age and year. We compared characteristics of cases and controls using standardized differences.

RESULTS

In both designs, VE estimates for the early years postimmunization were consistent with clinical trials (TND, 84%; FMD, 89% at 1-3 years postvaccination) but diverged as time since last vaccination increased (TND, 41%; FMD, 74% by 8 years postvaccination). Overall, we observed lower VE and faster waning in the TND than the FMD. In the TND but not FMD, controls differed from cases in important confounders, being younger, having more comorbidities, and higher healthcare use. Differences between the controls of each design were greater than differences between cases. TND controls were more likely to be unvaccinated or incompletely vaccinated than FMD controls (P < .001).

CONCLUSIONS

The FMD adjusted better for healthcare-seeking behavior than the TND. Duration of protection from pertussis vaccines is unclear because estimates vary by study design. Caution should be exercised by experts, researchers, and decision makers when evaluating evidence on optimal timing of boosters.

Re-investigating the coughing rat model of pertussis to understand Bordetella pertussis pathogenesis

Bordetella pertussis is a highly contagious bacterium that is the causative agent of whooping cough (pertussis). Currently, acellular pertussis vaccines (aP, DTaP, and Tdap) are used to prevent pertussis disease. However, it is clear that the aP vaccine efficacy quickly wanes, resulting in the reemergence of pertussis. Furthermore, recent work performed by the CDC suggest that current circulating strains are genetically distinct from strains of the past. The emergence of genetically diverging strains, combined with waning aP vaccine efficacy, calls for reevaluation of current animal models of pertussis. In this study, we used the rat model of pertussis to compare two genetically divergent strains Tohama 1 and D420. We intranasally challenged 7-week-old Sprague-Dawley rats with 10⁸ viable Tohama 1 and D420 and measured the hallmark signs/symptoms of B. pertussis infection such as neutrophilia, pulmonary inflammation, and paroxysmal cough using whole-body plethysmography. Onset of cough occurred between 2 and 4 days after B. pertussis challenge, averaging five coughs per 15 min, with peak coughing occurring at day 8 postinfection, averaging upward of 13 coughs per 15 min. However, we observed an increase of coughs in rats infected with clinical isolate D420 through 12 days postchallenge. The rats exhibited increased bronchial restriction following B. pertussis infection. Histology of the lung and flow cytometry confirm both cellular infiltration and pulmonary inflammation. D420 infection induced higher production of anti-B. pertussis IgM antibodies compared to Tohama 1 infection. The coughing rat model provides a way of characterizing disease manifestation differences between B. pertussis strains.

Decline of serologic immunity to diphtheria, tetanus and pertussis with age suggested a full life vaccination in mainland China

Background: Diphtheria-tetanus-pertussis (DTP) vaccine has already been involved in national vaccination program for several decades in China. The immunity against these diseases in the people of all ages is not well investigated.Materials and methods: Serum samples were tested for IgG antibodies to diphtheria toxoid (DT), tetanus toxoid (TT) and pertussis toxin (PT) by using commercial ELISA kits.Results: A total of 666 sera of patients from 1 day to 89 years of age was collected from 2018 to 2019. The protective rates of diphtheria, tetanus and pertussis were 45.5%, 54.4% and 4.7%, respectively. Only 4.7% of the study population had seropositivity against three of the diseases. Young infant (<3 m) and adult (>18y) were generally lack of protective antibody against diphtheria (81.7% and 58.3%) and tetanus (91.5% and 86.2%). An obvious increase in immunity level of diphtheria and tetanus was observed at 3 m-3y, but there was no significant increase of immunity to pertussis at any age group. All age groups showed low immunity to pertussis.Conclusions: The present results revealed the susceptibility to diphtheria and tetanus in young infants and adults, and the susceptibility to pertussis over the ages, which highlight the need to improve the current vaccination program.

A system-view of Bordetella pertussis booster vaccine responses in adults primed with whole-cell versus acellular vaccine in infancy

The increased incidence of whooping cough worldwide suggests that current vaccination against Bordetella pertussis infection has limitations in quality and duration of protection. The resurgence of infection has been linked to the introduction of acellular vaccines (aP), which have an improved safety profile compared with the previously used whole-cell (wP) vaccines. To determine immunological differences between aP and wP priming in infancy, we performed a systems approach of the immune response to booster vaccination. Transcriptomic, proteomic, cytometric, and serologic profiling revealed multiple shared immune responses with different kinetics across cohorts, including an increase of blood monocyte frequencies and strong antigen-specific IgG responses. Additionally, we found a prominent subset of aP-primed individuals (30%) with a strong differential signature, including higher levels of expression for CCL3, NFKBIA, and ICAM1. Contrary to the wP individuals, this subset displayed increased PT-specific IgE responses after boost and higher antigen-specific IgG4 and IgG3 antibodies against FHA and FIM2/3 at baseline and after boost. Overall, the results show that, while broad immune response patterns to Tdap boost overlap between aP- and wP-primed individuals, a subset of aP-primed individuals present a divergent response. These findings provide candidate targets to study the causes and correlates of waning immunity after aP vaccination.

Pertussis among patients with clinically compatible illness in the Amhara Regional State, Ethiopia

BACKGROUND

Pertussis is an acute respiratory tract disease caused by Bordetella pertussis. In 2014, 24.1 million pertussis cases, resulting in 160,700 deaths, were estimated to have occurred worldwide. This study aimed to determine the epidemiology of pertussis among patients with clinically compatible illness who visited selected hospitals in the Amhara Regional State of Ethiopia.

METHODS

A cross-sectional study design was used to review pertussis patients with clinically compatible illness. Nasopharyngeal swabs were collected from 515 patients from July 2018 through February 2019. DNA was extracted from all nasopharyngeal swabs and samples were analyzed using real-time (RT-) PCR. Crude and adjusted odds ratios with corresponding 95% confidence intervals were estimated using bivariable and multivariable logistic regression analysis, respectively.

RESULTS

The overall prevalence of Bordetella species among the study participants was 156 of 515 (30.3%) [95% CI = 26.4-34.6] as determined by Bordetella RT-PCR, including: 65 (41.7%) B. pertussis, 89 (57.1%) indeterminate B. pertussis, one (0.6%) Bordetella holmesii and one (0.6%) Bordetella parapertussis.

CONCLUSIONS

This study found that pertussis is potentially endemic and a common health problem among patients visiting health institutions in the Amhara Regional State of Ethiopia. More data regarding pertussis in Ethiopia could inform development of effective prevention strategies.

Circulation of Bordetella pertussis in vaccinated Cambodian children: A transversal serological study

BACKGROUND

The Cambodia pertussis immunization schedule includes three doses given at age 6, 10 and 14 weeks using a whole-pertussis vaccine. No booster doses are included. Pertussis biological diagnosis is unavailable in Cambodia and its burden remains unclear. This study aimed to provide accurate data on pertussis serological status of Cambodian children and adolescents, and to evaluate vaccination timeliness.

METHODS

Fully vaccinated children aged 3-15 years were recruited at the Rabies Prevention Center, Institut Pasteur in Cambodia, Phnom Penh. Capillary blood samples and information on pertussis vaccination history were collected. Anti-pertussis toxin (PT) IgG titers were quantified by ELISA.

RESULTS

Compliance with the national immunization schedule was 95.1%. Initiation of vaccination after 8 weeks of age was observed for 29.0% of the children, but was less frequent in the youngest children (13.0%) compared with the oldest ones (46.4%). Rate of children exhibiting anti-PT IgG varied across age groups, and increased from 35.7% to 55.0% in 3-5 and 12-15 years age groups, respectively.

CONCLUSION

Pertussis circulates among vaccinated Cambodian children and adolescents. These data support the need for public health authorities to strengthen pertussis surveillance and use local epidemiological data to make evidence-based decision for the establishment of an optimal vaccination strategy.

Seroprevalence of pertussis in Madagascar and implications for vaccination

Pertussis is a highly contagious infectious disease and remains an important cause of mortality and morbidity worldwide. Over the last decade, vaccination has greatly reduced the burden of pertussis. Yet, uncertainty in individual vaccination coverage and ineffective case surveillance systems make it difficult to estimate burden and the related quantity of population-level susceptibility, which determines population risk. These issues are more pronounced in low-income settings where coverage is often overestimated, and case numbers are under-reported. Serological data provide a direct characterisation of the landscape of susceptibility to infection; and can be combined with vaccination coverage and basic theory to estimate rates of exposure to natural infection. Here, we analysed cross-sectional data on seropositivity against pertussis to identify spatial and age patterns of susceptibility in children in Madagascar. A large proportion of individuals surveyed were seronegative; however, there were patterns suggestive of natural infection in all the regions analysed. Improvements in vaccination coverage are needed to help prevent additional burden of pertussis in the country.

Assessment of Pertussis Vaccine Protective Effectiveness in Children in the Amhara Regional State, Ethiopia

Background

Bordetella pertussis is a human pathogen which causes pertussis, or whooping cough. The diphtheria-tetanus-pertussis immunization has significantly reduced the morbidity and mortality of pertussis globally. However, higher prevalence and resurgence of pertussis cases among both vaccinated and unvaccinated people has raised questions on the effectiveness of pertussis vaccine over time. Therefore, the objective of this study was to assess the protective effectiveness of pertussis vaccine in the Amhara Regional State, Ethiopia.

Methods

A nested matched case-control study design approach was used with vaccinated individuals as cases and unvaccinated individuals as controls. The study was conducted from July 2018 to February 2019. Real-time (RT-) PCR assay was done to ascertain the presence of pertussis among clinically suspected patients. Bivariable and multivariable logistic regression analyses were computed to estimate the crude and adjusted odds ratios (ORs), respectively. Vaccine effectiveness was calculated as (1 − OR) × 100. Adjusted OR with 95% CI and a P value <0.05 were used to assess statistical significance.

Results

A total of 112 vaccinated and 223 unvaccinated controls were enrolled for the study. Of the total participants, 173/335 (51.6%) were males. The prevalence of pertussis among vaccinated was 35/112 (31.3%), whereas it was 84/223 (37.7%) among the control group. The adjusted matched vaccine protective effectiveness against B. pertussis infection following three doses of whole-cell vaccine was 25% among children aged between 6 and 9 years. Adjusted estimates of vaccine protective effectiveness for participants who had complete vaccination, stratified by time since last vaccination, were 50% at 6 years, 34% at 7 years, and 2% at 8–9 years since last vaccination.

Conclusion

Despite the availability and good coverage of childhood vaccination, the effectiveness of pertussis vaccine was found to be low in the Amhara region, Ethiopia. Moreover, we observed declining trends in the protective effectiveness of the vaccine after 6 years of vaccination. Thus, by considering the waning nature of immune response which is induced by whole-cell vaccine during early life, booster dose is highly recommended to optimize pertussis prevention and control strategies.

Severe Pertussis Infections in the United States, 2011-2015

Background

The incidence of pertussis in the United States has increased in recent years. While characteristics of severe pertussis infection have been described in infants, fewer data are available in older children and adults. In this analysis, we characterize pertussis infections in hospitalized patients of all ages.

Methods

Cases of pertussis with cough onset from 1 January 2011 through 31 December 2015 from 7 US Emerging Infections Program Network states were reviewed. Additional information on hospitalized patients was obtained through abstraction of the inpatient medical record. Descriptive and multivariable analyses were conducted to characterize severe pertussis infection and identify potential risk factors.

Results

Among 15942 cases of pertussis reported, 515 (3.2%) were hospitalized. Three hospitalized patients died. Infants aged <2 months accounted for 1.6% of all pertussis cases but 29.3% of hospitalizations. Infants aged 2–11 months and adults aged ≥65 years also had high rates of hospitalization. Infants aged <2 months whose mothers received acellular pertussis during the third trimester and children aged 2 months to 11 years who were up to date on pertussis-containing vaccines had a 43%–66% reduced risk of hospitalization. Among adolescents aged 12–20 years, 43.5% had a history of asthma, and among adults aged ≥65 years, 26.8% had a history of chronic obstructive pulmonary disease.

Conclusions

Individuals at the extreme ends of life may be the most vulnerable to severe pertussis infections, though hospitalization was reported across all age groups. Continued monitoring of severe pertussis infections will be important to help guide prevention, control, and treatment options.

Comparison of whole-cell versus acellular pertussis vaccine effectiveness in school clusters of pertussis, France, 2013

OBJECTIVES AND METHOD

We conducted a prospective study in 2013 to compare the whole-cell versus acellular pertussis vaccines effectiveness and duration of protection, following the occurrence of pertussis clusters.

RESULTS

During seven school outbreaks, we identified 102 clinical pertussis cases, including 10 cases biologically confirmed by Bordetella pertussis specific PCR, among a cohort of 305 children in 2nd to 6th grade. The risk of pertussis when vaccinated with an acellular vaccine alone was 1.6 (RR=1.6; 95% CI=1.1-2.5) times higher than when vaccinated with a whole-cell vaccine or using a combined schedule.

CONCLUSIONS

The limited duration of protection conferred by the acellular vaccine reinforces the 2013 introduction of the pertussis booster at six years old.

Uncovering Distinct Primary Vaccination-Dependent Profiles in Human Bordetella Pertussis Specific CD4+ T-Cell Responses Using a Novel Whole Blood Assay

To advance research and development of improved pertussis vaccines, new immunoassays are needed to qualify the outcome of Bordetella pertussis (Bp) specific CD4+ T-cell differentiation. Here, we applied a recently developed whole blood assay to evaluate Bp specific CD4+ T-cell responses. The assay is based on intracellular cytokine detection after overnight in vitro Bp antigen stimulation of diluted whole blood. We show for the first time that CD4+ T-cell memory of Th1, Th2, and Th17 lineages can be identified simultaneously in whole blood. Participants ranging from 7 to 70 years of age with different priming backgrounds of whole-cell pertussis (wP) and acellular pertussis (aP) vaccination were analyzed around an acellular booster vaccination. The assay allowed detection of low frequent antigen-specific CD4+ T-cells and revealed significantly elevated numbers of activated and cytokine-producing CD4+ T-cells, with a significant tendency to segregate recall responses based on primary vaccination background. A stronger Th2 response hallmarked an aP primed cohort compared to a wP primed cohort. In conclusion, analysis of Bp specific CD4+ T-cell responses in whole blood showed separation based on vaccination background and provides a promising tool to assess the quantity and quality of CD4+ T-cell responses induced by vaccine candidates.

Key steps in vaccine development

OBJECTIVE

The goal of a vaccine is to prime the immune response so the immune memory can facilitate a rapid response to adequately control the pathogen on natural infection and prevent disease manifestation. This article reviews the main elements that provide for the development of safe and effective vaccines.

DATA SOURCES

Literature covering target pathogen epidemiology, the key aspects of the functioning immune response underwriting target antigen selection, optimal vaccine formulation, preclinical and clinical trial studies necessary to deliver safe and efficacious immunization.

STUDY SELECTIONS

Whole live, inactivated, attenuated, or partial fractionated organism-based vaccines are discussed in respect of the balance of reactogenicity and immunogenicity. The use of adjuvants to compensate for reduced immunogenicity is described. The requirements from preclinical studies, including establishing a proof of principle in animal models, the design of clinical trials with healthy volunteers that lead to licensure and beyond are reviewed.

RESULTS

The 3 vaccine development phases, preclinical, clinical, and post-licensure, integrate the requirements to ensure safety, immunogenicity, and efficacy in the final licensed product. Continuing monitoring of efficacy and safety in the immunized populations is essential to sustain confidence in vaccination programs.

CONCLUSION

In an era of increasing vaccine hesitancy, the need for a better and widespread understanding of how immunization acts to counteract the continuing and changing risks from the pathogenic world is required. This demands a societal responsibility for obligate education on the benefits of vaccination, which as a medical intervention has saved more lives than any other procedure.

Vaccination of Adults in General Medical Practice

In vaccinating adults, clinicians face 2 types of challenges: (1) staying current on recommendations for influenza, pneumococcal, hepatitis A and B, zoster, and other vaccines and (2) addressing systemic barriers to implementing practices that increase vaccination rates. Although adult immunization rates remain suboptimal, there has been much good news in adult vaccination recently. New high-dose and adjuvanted influenza vaccines help improve immune response and may reduce influenza complications in older adults. The new recombinant zoster vaccine offers significantly more efficacy against zoster outbreaks and postherpetic neuralgia than zoster vaccine live. Pertussis vaccine given during the third trimester of pregnancy may prevent between 50% and 90% of pertussis infections in infants. Shorter time for completion (1 vs 6 months) of new, adjuvanted hepatitis B vaccine may increase adherence. Clinicians can address systemic barriers to increasing vaccination rates in their clinics and health care systems by following the Centers for Disease Control and Prevention's Standards for Adult Immunization Practice. Clinicians can help increase vaccination rates by writing standing orders and by advocating for nurses or medical assistants to receive training and protected time for assessing and documenting vaccination histories and administration. Strong recommendations that presume acceptance of vaccination are effective with most patients. Communication techniques similar to motivational interviewing can help with vaccine-hesitant patients. Clinicians, as experts on providing preventive services, can educate community leaders about the benefits of immunization and can inform vaccine experts about challenges of implementing vaccination recommendations in clinical practice and strategies that can work to raise vaccination rates.

Comment on "The impact of past vaccination coverage and immunity on pertussis resurgence"

Limitations in the data used for a recent modeling study of pertussis resurgence in the US may explain why the results were not consistent with several observational studies demonstrating a shorter duration of protection after acellular pertussis vaccine administration.

Pertussis seronegativity in pregnant women in the city of Al Ain, United Arab Emirates

OBJECTIVE

As the current recommendation of administering Tdap (tetanus-diphtheria-acellular pertussis) to all pregnant women has not been widely implemented in the United Arab Emirates (UAE), we aimed to ascertain the prevalence of pertussis seronegativity during pregnancy.

METHODS

IgG antibodies against Bordetella pertussis toxin (PT) were measured in 213 women attending the antenatal clinic at Oasis hospital, Al Ain, UAE. Results were compared by maternal age, nationality and gestational age with the Kruskal-Wallis test for IgG-PT levels and the Chi-squared test for serology status.

RESULTS

The mean age±SD of the participants was 30.4±5.6 years, mean gestational age±SD of 25.5±3.3 weeks. Serum concentration of IgG-PT <10IU/ml were found in 160 out of 213 women (75%; 95% confidence interval 69%, 81%). There was no significant difference in the geometric mean of serum IgG-PT concentration across maternal age (P=0.80) or nationality (P=0.90). There were no differences in the prevalence of seronegativity with maternal age (P=0.65) or nationality (P=0.90).

CONCLUSION

With a high prevalence of pertussis seronegativity in pregnant women, there is a potential benefit of introducing pertussis vaccination during pregnancy into our national immunization program.

Pertussis Vaccination Failure in the New Zealand Pediatric Population: Study Protocol

Pertussis vaccines have been effective at reducing pertussis-associated morbidity and mortality. However, they have a complex array of limitations, particularly associated with the duration of protection against clinical disease and imperfect immunity (carriage and transmission). Little is known about risk factors for pertussis vaccination failure. Understanding pertussis vaccination failure risk is most important in the paediatric population. This study aims to investigate risk factors for pertussis vaccination failure in (1) infants between birth and six weeks of age born to mothers who received pertussis booster vaccinations during pregnancy and (2) infants after the completion of the primary series (approximately five months old) to four years old. This will be achieved in a two-step process for each study group. Pertussis vaccination failure cases will first be described using a case series study design, relevant case characteristics will be sourced from six national administrative datasets. The case series study results will help select candidate risk factors (hypothesis generating step) to be tested in the retrospective cohort study (hypothesis testing step. Pattern analysis will be used to investigate risk factor patterns in the cohort study. The identification of higher risk groups enables targeting strategies, such as additional doses, to better prevent pertussis disease.

Randomized study of immune responses to two Tdap vaccines among adolescents primed with DTaP and comparison with results among adolescents primed with DTwP

BACKGROUND

It has been reported that persons primed with acellular (DTaP) pertussis vaccines have reduced duration of pertussis protection compared with those primed with whole-cell (DTwP) vaccines. However, due to the rapid transition to acellular vaccines, studies attempting directly to compare protection among DTaP-primed vs DTwP-primed individuals are subject to confounding by age and other limitations of ecological studies. Using validated assay results and stored sera from multiple Tdap studies, we evaluated two licensed Tdap vaccines among DTaP-primed adolescents to allow comparison with results obtained in the same laboratory from earlier studies involving DTwP-primed adolescents.

METHODS

Participants 11-12 years of age who had received exactly 5 doses of DTaP vaccine prior to 7 years of age were randomly assigned in 2012 to receive one of two licensed Tdap vaccines. Serum specimens obtained pre- and post-vaccination were assayed for responses to the vaccines. Current results were then compared to results obtained in the same laboratory from prior randomized Tdap studies conducted among adolescents primed with DTwP or DTaP.

RESULTS

Both Tdap vaccines produced strong antibody responses to diphtheria and tetanus; responses to contained pertussis antigens were consistent with the differing levels of those antigens in each Tdap vaccine. However, postvaccination pertussis antibody responses were as much as 71% lower in these DTaP-primed adolescents compared with responses among DTwP-primed adolescents in a prior study of the same two Tdap vaccines. In contrast, results from the present study were similar to those seen in another study of Tdap among DTaP-primed adolescents.

DISCUSSION

Taken together, these results from randomized clinical trials provide direct evidence of reduced antibody responses to both licensed Tdap vaccines among adolescents primed with DTaP vaccine, compared with adolescents primed with DTwP vaccine. Clinical trial registry number: ClinicalTrials.gov, NCT01629589.

Spatio-temporal comparison of pertussis outbreaks in Olmsted County, Minnesota, 2004-2005 and 2012: a population-based study

OBJECTIVE

Two pertussis outbreaks occurred in Olmsted County, Minnesota, during 2004-2005 and 2012 (5-10 times higher than other years), with significantly higher incidence than for the State. We aimed to assess whether there were similar spatio-temporal patterns between the two outbreaks.

SETTING

Olmsted County, Minnesota, USA PARTICIPANTS: We conducted a population-based retrospective cohort study of all Olmsted County residents during the 2004-2005 and 2012 outbreaks, including laboratory-positive pertussis cases.

PRIMARY OUTCOME MEASURE

For each outbreak, we estimated (1) age-specific incidence rate using laboratory-positive pertussis cases (numerator) and the Rochester Epidemiology Project Census (denominator), a medical record-linkage system for virtually all Olmsted County residents, and (2) pertussis case density using kernel density estimation to identify areas with high case density. To account for population size, we calculated relative difference of observed density and expected density based on age-specific incidence.

RESULTS

We identified 157 and 195 geocoded cases in 2004-2005 and 2012, respectively. Incidence was the highest among adolescents (ages 11 to <14 years) for both outbreaks (9.6 and 7.9 per 1000). The 2004-2005 pertussis outbreak had higher incidence in winter (52% of cases) versus summer in 2012 (53%). We identified a consistent area with higher incidence at the beginning (ie, first quartile) of two outbreaks, but it was inconsistent for later quartiles. The relative difference maps for the two outbreaks suggest a greater role of neighbourhood population size in 2012 compared with 2004-2005.

CONCLUSIONS

Comparing spatio-temporal patterns between two pertussis outbreaks identified a consistent geographical area with higher incidence of pertussis at the beginning of outbreaks in this community. This finding can be tested in future outbreaks, and, if confirmed, can be used for identifying epidemiological risk factors clustered in such areas for geographically targeted intervention.

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.

Neonatal Immunity to Bordetella pertussis Infection and Current Prevention Strategies

Bordetella pertussis is the bacterial agent of whooping cough, an infectious disease that is reemerging despite high vaccine coverage. Newborn children are the most affected, not only because they are too young to be vaccinated but also due to qualitative and quantitative differences in their immune system, which makes them more susceptible to infection and severe manifestations, leading to a higher mortality rate comparing to other groups. Until recently, prevention consisted of vaccinating children in the first year of life and the herd vaccination of people directly in touch with them, but the increase in cases demands more effective strategies that can overcome the developing immune response in early life and induce protection while children are most vulnerable.

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.

A Review on T Cell Epitopes Identified Using Prediction and Cell-Mediated Immune Models for Mycobacterium tuberculosis and Bordetella pertussis

In the present review, we summarize work from our as well as other groups related to the characterization of bacterial T cell epitopes, with a specific focus on two important pathogens, namely, Mycobacterium tuberculosis (Mtb), the bacterium that causes tuberculosis (TB), and Bordetella pertussis (BP), the bacterium that causes whooping cough. Both bacteria and their associated diseases are of large societal significance. Although vaccines exist for both pathogens, their efficacy is incomplete. It is widely thought that defects and/or alteration in T cell compartments are associated with limited vaccine effectiveness. As discussed below, a full genome-wide map was performed in the case of Mtb. For BP, our focus has thus far been on the antigens contained in the acellular vaccine; a full genome-wide screen is in the planning stage. Nevertheless, the sum-total of the results in the two different bacterial systems allows us to exemplify approaches and techniques that we believe are generally applicable to the mapping and characterization of human immune responses to bacterial pathogens. Finally, we add, as a disclaimer, that this review by design is focused on the work produced by our laboratory as an illustration of approaches to the study of T cell responses to Mtb and BP, and is not meant to be comprehensive, nor to detract from the excellent work performed by many other groups.

Increasing FIM2/3 antigen-content improves efficacy of Bordetella pertussis vaccines in mice in vivo without altering vaccine-induced human reactogenicity biomarkers in vitro

Current acellular-pertussis (aP) vaccines appear inadequate for long-term pertussis control because of short-lived efficacy and the increasing prevalence of pertactin-negative isolates which may negatively impact vaccine efficacy. In this study, we added fimbriae (FIM)2 and FIM3 protein to licensed 2-, 3- or 5-component aP vaccines (Pentavac®, Boostrix®, Adacel®, respectively) to assess whether an aP vaccine with enhanced FIM content demonstrates enhanced efficacy. Vaccine-induced protection was assessed in an intranasal mouse challenge model. In addition, potential reactogenicity was measured by biomarkers in a human whole blood assay (WBA) in vitro and benchmarked the responses against licensed whole cell pertussis (wP) and aP vaccines including Easyfive®, Pentavac® and Pentacel®. The results show that commercial vaccines demonstrated reduced efficacy against pertactin-negative versus pertactin-positive strains. However, addition of higher amounts of FIM2/3 to aP vaccines reduced lung colonization and increased vaccine efficacy against a pertactin-negative strain in a dose-dependent manner. Improvements in efficacy were similar for FIM2 and FIM3-expressing strains. Increasing the amount of FIM2/3 proteins in aP formulations did not alter vaccine-induced biomarkers of potential reactogenicity including prostaglandin E₂, cytokines and chemokines in human newborn cord and adult peripheral blood tested in vitro. These results suggest that increasing the quantity of FIM proteins in current pertussis vaccine formulations may further enhance vaccine efficacy against B. pertussis infection without increasing the reactogenicity of the vaccine.

Recommendations to control pertussis prioritized relative to economies: A Global Pertussis Initiative update

Pertussis is a vaccine-preventable disease that causes morbidity and mortality, particularly in infants and children <5 years of age. The Global Pertussis Initiative (GPI) recommendations represent a systematic evaluation and prioritization of strategies to prevent pertussis-related infant and child deaths, reduce global disease burden and prevent resurgence through vaccination strategies and public health policies at national, regional and local levels. The GPI recommendations are based on clinical trials and observational and surveillance data, which are essential in the planning, implementation and evaluation of vaccination practices and best use of available resources. Many low- and middle-income countries (LMIC) continue to use whole-cell pertussis (wP) vaccines for primary vaccination, while most high-income countries have replaced wP with the less-reactogenic acellular pertussis (aP) vaccines. This present manuscript pertains to discussions held during the GPI's meeting on November 11-13, 2016, in Cape Town, Republic of South Africa. The GPI recommends that LMIC aim for high coverage of infant series pertussis vaccines as a priority. In LMIC and countries with constrained vaccine funding, if wP vaccines are currently used, wP should continue to be used. Furthermore, given that protection against disease and death due to pertussis in neonates is a key priority of the GPI, it recommends that ap immunization in pregnancy should be implemented as a priority in all countries if resources allow. Given that surveillance and epidemiology data on which to base vaccine decisions are important, the GPI also suggests that, in areas where wP vaccines are implemented, standardization and calibration of wP vaccines are checked, considering the many different manufacturers and variable standards of production and quality control. In addition, as immunity to pertussis wanes following the primary infant series of vaccination, the GPI further recommends that toddlers, adolescents, healthcare and childcare workers receive booster vaccine doses, where resources allow.

Th1/Th17 polarization persists following whole-cell pertussis vaccination despite repeated acellular boosters

In the mid-1990s, whole-cell pertussis (wP) vaccines were associated with local and systemic adverse events that prompted their replacement with acellular pertussis (aP) vaccines in many high-income countries. In the past decade, rates of pertussis disease have increased in children receiving only aP vaccines. We compared the immune responses to aP boosters in individuals who received their initial doses with either wP or aP vaccines using activation-induced marker (AIM) assays. Specifically, we examined pertussis-specific memory CD4+ T cell responses ex vivo, highlighting a type 2/Th2 versus type 1/Th1 and Th17 differential polarization as a function of childhood vaccination. Remarkably, after a contemporary aP booster, cells from donors originally primed with aP were (a) associated with increased IL-4, IL-5, IL-13, IL-9, and TGF-β and decreased IFN-γ and IL-17 production, (b) defective in their ex vivo capacity to expand memory cells, and (c) less capable of proliferating in vitro. These differences appeared to be T cell specific, since equivalent increases of antibody titers and plasmablasts after aP boost were seen in both groups. In conclusion, our data suggest that there are long-lasting effects and differences in polarization and proliferation of T cell responses in adults originally vaccinated with aP compared with those that initially received wP, despite repeated acellular boosters.

Composition of pertussis vaccine given to infants determines long-term T cell polarization

The introduction of a whole-cell vaccine against Bordetella pertussis, the causative agent of whooping cough, dramatically reduced disease incidence. Unfortunately, the whole-cell formulation also induces severe reactions in some infants. Because of this, acellular vaccines have been developed, but they are used exclusively in high-income countries. However, the acellular vaccines do not provide long-term protection, and despite the use of routine boosters, the disease is on the rise. In this issue of the JCI, da Silva Antunes and colleagues demonstrate that the whole-cell vaccines promote long-term polarization toward Th1 and Th17 responses, while the acellular vaccines induce Th2 polarization. Moreover, this polarization is long term, as the response to acellular boosters is dependent on the initial vaccine given in infancy. The authors speculate that Tregs may be induced by initial acellular vaccine administration. The results of this study have important implications for the development of pertussis vaccination strategies that would induce Th1 and Th17 polarization.

Assessment of Tdap Vaccination Effectiveness in Adolescents in Integrated Health-Care Systems

PURPOSE

Despite high national vaccination coverage with tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccines among U.S. adolescents, rates of adolescent pertussis disease are increasing. We estimated the duration of protection after Tdap vaccination and the possible effects of the change from whole-cell to acellular childhood pertussis vaccines in the United States during the 1990s.

METHODS

We conducted a retrospective cohort analysis among 11- to 18-year-olds enrolled in two integrated health-care delivery systems during 2005-2012. Cases met the Council of State and Territorial Epidemiologists' confirmed or probable definition or a polymerase chain reaction-positive suspect definition. We estimated vaccine effectiveness (VE) overall and by time since Tdap receipt. We stratified VE estimates by primary series pertussis vaccine received (based on birth year): mixed-vaccine cohort (1987-1997) and acellular vaccine cohort (1998-2001).

RESULTS

The overall Tdap VE was 57% (95% confidence interval [CI]: 42%-68%); the VE in the mixed-vaccine and acellular cohorts was 65% (95% CI: 44%-78%) and 52% (95% CI: 30%-68%), respectively. Tdap VE within <2 years post vaccination (69%, 95% CI: 54%-79%) was significantly different from VE ≥2 years post vaccination (34%, 95% CI: 1%-55%, p value < .01). VE was significantly higher <2 years post vaccination compared with ≥2 years post vaccination in both mixed-vaccine (87%, 95% CI: 58%-96%, and 52%, 95% CI: 13%-73%; p value = .04) and acellular cohorts (62%, 95% CI: 41%-76%, and 21%, 95% CI: -30% to 52%; p value = .01).

CONCLUSIONS

Although Tdap vaccination remains the best pertussis prevention method for adolescents, protection wanes within 2 years regardless of the type of childhood primary vaccine. Vaccines with longer duration of protection could decrease pertussis burden.

Reduced Severity of Pertussis in Persons With Age-Appropriate Pertussis Vaccination-United States, 2010-2012

Background

In 2012, >48000 pertussis cases were reported in the United States. Many cases occurred in vaccinated persons, showing that pertussis vaccination does not prevent all pertussis cases. However, pertussis vaccination may have an impact on disease severity.

Methods

We analyzed data on probable and confirmed pertussis cases reported through Enhanced Pertussis Surveillance (Emerging Infections Program Network) between 2010 and 2012. Surveillance data were collected through physician and patient interview and vaccine registries. We assessed whether having received an age-appropriate number of pertussis vaccines (AAV) (for persons aged ≥3 months) was associated with reduced odds of posttussive vomiting, a marker of more clinically significant illness, or of severe pertussis (seizure, encephalopathy, pneumonia, and/or hospitalization). Adjusted odds ratios were calculated using multivariable logistic regression.

Results

Among 9801 pertussis patients aged ≥3 months, 77.6% were AAV. AAV status was associated with a 60% reduction in odds of severe disease in children aged 7 months-6 years in multivariable logistic regression and a 30% reduction in odds of posttussive vomiting in persons aged 19 months-64 years.

Conclusions

Serious pertussis symptoms and complications are less common among AAV pertussis patients, demonstrating that the positive impact of pertussis vaccination extends beyond decreasing risk of disease.

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

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

Immunogenicity and safety of a second booster dose of an acellular pertussis vaccine combined with reduced antigen content diphtheria-tetanus toxoids 10 years after a first booster in adolescence: An open, phase III, non-randomized, multi-center study

Pertussis is a highly contagious disease, for which periodic peaks in incidence and an increasing number of outbreaks have been observed over the last decades. The reduced-antigen-content tetanus-diphtheria-acellular pertussis vaccine (Tdap) can be used to boost individuals aged ≥10 years, vaccinated in infancy with a diphtheria-tetanus-acellular pertussis vaccine (DTaP), to reduce pertussis morbidity and maintain protection against diphtheria and tetanus throughout adolescence and adulthood. This phase III, open-label, non-randomized, multicenter follow-up study (NCT01738477) enrolled 19–30-year-old participants from the United States who had received booster vaccination 10 years earlier with either Tdap (Tdap group) or Td (Td group). In total, 128 (Tdap group) and 37 (Td group) participants received Tdap vaccination. After administration of Tdap, all participants were seroprotected (antibody concentrations ≥0.1 international units [IU]/ml) against diphtheria and tetanus. Immune responses to a second Tdap dose in the Tdap group were shown to be non-inferior to responses elicited by a first Tdap dose in the Td group for diphtheria and tetanus and to a 3-dose DTaP vaccination during infancy for pertussis antigens (primary objectives). Post-booster vaccination, all participants in both groups had antibody concentrations above assay cut-offs and antibody geometric mean concentrations increased by 3.8–15.5-fold compared to pre-booster levels for all antigens. The incidence of adverse events was similar in the Td (80.6%) and Tdap (85.6%) groups (no serious adverse events reported). A Tdap dose administered after previous Td or Tdap vaccination was shown to be immunogenic and well-tolerated in young adults, supporting repeated vaccination with Tdap at 10-year intervals.

Surveillance of Circulating Bordetella pertussis Strains in Europe during 1998 to 2015

One reason for increased pertussis incidence is the adaptation of Bordetella pertussis to vaccine-induced immunity by modulating its genomic structure. This study, EUpert IV, includes 265 isolates collected from nine European countries during 2012 to 2015 (n = 265) and compares the results to previous EUpert I to III studies (1998 to 2009). The analyses included genotyping, serotyping, pulsed-field gel electrophoresis (PFGE), and multilocus variable-number tandem-repeat analysis (MLVA). Genotyping results showed only small variations among the common virulence genes of B. pertussis The frequencies of serotypes Fim2 and Fim3 varied among the four collections. Genomic analyses showed that MLVA type 27 increased to 80% between the periods of 1998 to 2001 and 2012 to 2015. Two PFGE profiles, BpSR3 (29.4%) and BpSR10 (27.2%), constituted more than 50% of the circulating isolates in the present collection. Our study indicates that the European B. pertussis population is changing and became more homogenous after the introduction of acellular pertussis vaccines.

An Assessment of the Cocooning Strategy for Preventing Infant Pertussis-United States, 2011

BACKGROUND

 Infants are at greatest risk for severe pertussis. In 2006, the Advisory Committee on Immunization Practices recommended that adolescents and adults, especially those with infant contact, receive a single dose of Tdap (tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine). To assess the effectiveness of cocooning, we conducted a case-control evaluation of infant close contacts.

METHODS

 Pertussis cases aged <2 months with onset between 1 January 2011 and 31 December 2011 were identified in Emerging Infections Program Network sites. For each case, we recruited 3 controls from birth certificates and interviewed identified adult close contacts (CCs) or parents of CCs aged <18 years. Pertussis vaccination was verified through medical providers and/or immunization registries.

RESULTS

 Forty-two cases were enrolled, with 154 matched controls. Around enrolled infants, 859 CCs were identified (600 adult and 259 nonadult). An average of 5.4 CCs was identified per case and 4.1 CCs per control. Five hundred fifty-four (64.5%) CCs were enrolled (371 adult and 183 non-adult CCs); 119 (32.1% of enrolled) adult CCs had received Tdap. The proportion of Tdap-vaccinated adult CCs was similar between cases and controls (P = .89). The 600 identified adult CCs comprised 172 potential cocoons; 71 (41.3%) potential cocoons had all identified adult CCs enrolled. Of these, 9 were fully vaccinated and 43.7% contained no Tdap-vaccinated adults. The proportion of fully vaccinated case (4.8%) and control (10.0%) cocoons was similar (P = .43).

CONCLUSIONS

 Low Tdap coverage among adult CCs reinforces the difficulty of implementing the cocooning strategy and the importance of vaccination during pregnancy to prevent infant pertussis.