Evaluation of Whole-Cell and Acellular Pertussis Vaccines in the Context of Long-Term Herd Immunity

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.

Antibody persistence to diphtheria toxoid, tetanus toxoid, Bordetella pertussis antigens, and Haemophilus influenzae type b following primary and first booster with pentavalent versus hexavalent vaccines

Thailand has incorporated the whole-cell (wP) pertussis vaccine into the expanded program on immunization since 1977 and has offered the acellular pertussis (aP) vaccine as an optional vaccine for infants since 2001. We followed healthy children from a clinical trial (ClinicalTrials.gov NCT02408926) in which children were randomly assigned to receive either pentavalent (DTwP-HB-Hib) or hexavalent (DTaP-IPV-HB-Hib) vaccines for their primary series (administered at 2, 4, and 6 months) and first booster vaccination (18 months). Both groups received Tdap-IPV as a second booster at the age of 4 y. Blood samples were collected for evaluation of antibody persistence to diphtheria toxoid (DT), tetanus toxoid (TT), and Bordetella pertussis (B. pertussis) between 2 and 6 y of age annually, and for the immunogenicity study of Tdap-IPV at 1 month after the second booster. Antibody persistence to Haemophilus influenzae type b (Hib) was followed until 3 y of age. A total of 105 hexavalent-vaccinated children and 91 pentavalent-vaccinated children completed this study. Both pentavalent and hexavalent groups demonstrated increased antibody levels against DT, TT, and B. pertussis antigens following the second booster with Tdap-IPV. All children achieved a seroprotective concentration for anti-DT and anti-TT IgG at 1 month post booster. The hexavalent group possessed significantly higher anti-pertactin IgG (adjusted p = .023), whereas the pentavalent group possessed significantly higher anti-pertussis toxin IgG (adjusted p < .001) after the second booster. Despite declining levels post-second booster, a greater number of children sustained protective levels of anti-DT and anti-TT IgG compared to those after the first booster.

Pertussis vaccines, epidemiology and evolution

Pertussis, which is caused by Bordetella pertussis, has plagued humans for at least 800 years, is highly infectious and can be fatal in the unvaccinated, especially very young infants. Although the rollout of whole-cell pertussis (wP) vaccines in the 1940s and 1950s was associated with a drastic drop in incidence, concerns regarding the reactogenicity of wP vaccines led to the development of a new generation of safer, acellular (aP) vaccines that have been adopted mainly in high-income countries. Over the past 20 years, some countries that boast high aP coverage have experienced a resurgence in pertussis, which has led to substantial debate over the basic immunology, epidemiology and evolutionary biology of the bacterium. Controversy surrounds the duration of natural immunity and vaccine-derived immunity, the ability of vaccines to prevent transmission and severe disease, and the impact of evolution on evading vaccine immunity. Resolving these issues is made challenging by incomplete detection of pertussis cases, the absence of a serological marker of immunity, modest sequencing of the bacterial genome and heterogeneity in diagnostic methods of surveillance. In this Review, we lay out the complexities of contemporary pertussis and, where possible, propose a parsimonious explanation for apparently incongruous observations.

Increase of pertussis cases in the Vallès region, Catalonia, Spain, September 2023 to April 2024

We describe a pertussis outbreak in the Vallès region of Catalonia, from September 2023 to April 2024. Incidence was high in children aged 10-14 years compared with previous outbreaks. Limited impact in newborns could be explained by the high vaccination coverage during pregnancy and at 11 months of age in 2022, at 85% and 94.1 %, respectively. A third booster vaccine dose during preadolescence should be considered and vaccination coverage in pregnant women be improved to control future outbreaks.

Age associated susceptibility to SARS-CoV-2 infection in the K18-hACE2 transgenic mouse model

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still an ongoing global health crisis. Clinical data indicate that the case fatality rate (CFR) is age dependent, with a higher CFR percentage in the elderly population. We compared the pathogenesis of SARS-CoV-2 in young and aged K18-hACE2 transgenic mice. We evaluated morbidity, mortality, viral titers, immune responses, and histopathology in SARS-CoV-2-infected young and old K18-hACE2 transgenic mice. Within the limitation of having a low number of mice per group, our results indicate that SARS-CoV-2 infection resulted in slightly higher morbidity, mortality, and viral replication in the lungs of old mice, which was associated with an impaired IgM response and altered cytokine and chemokine profiles. Results of this study increase our understanding of SARS-CoV-2 infectivity and immuno-pathogenesis in the elderly population.

Comprehensive Overview of Treponema pallidum Outer Membrane Proteins

Treponema pallidum, the causative agent of syphilis, is a sexually transmitted microorganism that exhibits remarkable motility capabilities, allowing it to affect various systems. Despite its structural resemblance to gram-negative bacteria due to its dual-membrane, T. pallidum possesses a lower abundance of outer membrane proteins (OMPs), which enables it to effectively conceal itself. This review presents a comprehensive analysis of the clinical diagnostic potential associated with the OMPs of T. pallidum. Furthermore, the known OMPs in T. pallidum that are responsible for mediating host interactions have been progressively elucidated. This review aims to shed light on the pathogenesis of syphilis, encompassing aspects such as vascular inflammation, chancre self-healing, neuroinvasion, and reinfection. Additionally, this review offers a detailed overview of the current state and prospects of development in the field of syphilis vaccines, with the ultimate goal of establishing a foundation for understanding the pathogenesis and implementing effective prevention strategies against syphilis.

The role of vaccination in COPD: influenza, SARS-CoV-2, pneumococcus, pertussis, RSV and varicella zoster virus

Exacerbations of COPD are associated with worsening of the airflow obstruction, hospitalisation, reduced quality of life, disease progression and death. At least 70% of COPD exacerbations are infectious in origin, with respiratory viruses identified in approximately 30% of cases. Despite long-standing recommendations to vaccinate patients with COPD, vaccination rates remain suboptimal in this population.Streptococcus pneumoniae is one of the leading morbidity and mortality causes of lower respiratory tract infections. The Food and Drug Administration recently approved pneumococcal conjugate vaccines that showed strong immunogenicity against all 20 included serotypes. Influenza is the second most common virus linked to severe acute exacerbations of COPD. The variable vaccine efficacy across virus subtypes and the impaired immune response are significant drawbacks in the influenza vaccination strategy. High-dose and adjuvant vaccines are new approaches to tackle these problems. Respiratory syncytial virus is another virus known to cause acute exacerbations of COPD. The vaccine candidate RSVPreF3 is the first authorised for the prevention of RSV in adults ≥60 years and might help to reduce acute exacerbations of COPD. The 2023 Global Initiative for Chronic Lung Disease report recommends zoster vaccination to protect against shingles for people with COPD over 50 years.

Impact of maternal whole-cell or acellular pertussis primary immunization on neonatal immune response

With the introduction of pertussis immunization for pregnant women in many countries, there has been renewed interest in the impact of whole-cell pertussis vaccine (wP) versus acellular vaccine (aP) on disease control, particularly regarding the best approach for priming. To gather evidence on this topic, we analyzed the impact of aP or wP priming on aP vaccination during pregnancy (aPpreg) in mice. Two-mother vaccination schemes were employed (wP-wP-aPpreg and aP-aP-aPpreg), and the immune response in the mothers and their offspring, as well as the protection of the offspring against Bordetella pertussis challenge, were assessed. Pertussis toxin (PTx)-specific IgG responses were detected in mothers after both the second and third doses, with higher titers after the third dose, regardless of the vaccination schedule. However, a significant reduction in PTx-IgG levels was observed after 22 weeks post aPpreg immunization in mothers with the aP-aP-aPpreg scheme but not in the wP-wP-aPpreg immunized mothers. The aP-aP-aPpreg schedule triggered a murine antibody response mainly to a Th2-profile, while wP-wP-aPpreg induced a Th1/Th2 mixed profile. Both immunization schemes administered to the mothers protected the offspring against pertussis, but the wP-wP-aPpreg vaccination conferred offspring protection in all pregnancies at least up to 20 weeks after receiving the aPpreg-dose. In contrast, the immunity induced by aP-aP-aPpreg began to decline in births that occurred 18 weeks after receiving the aPpreg dose. For the aP-aP-aPpreg scheme, pups born from gestations furthest from aPpreg (+22 weeks) had lower PTx-specific IgG levels than those born closer to the application of the dose during pregnancy. In contrast, for pups born to wP-wP-aPpreg vaccinated mothers, the PTx-specific IgG levels were maintained over time, even for those born at the longest time studied (+22 weeks). It is noteworthy that only the pups born from mothers with aP-aP-aPpreg and receiving a neonatal dose of either aP or wP were more susceptible to B. pertussis infection than mice with only maternal immunity, suggesting interference with the induced immunity (p<0.05). However, it should be noted that mice with maternal immunity, whether vaccinated or not with neonatal doses, are better protected against colonization with B. pertussis than mice without maternal immunity but vaccinated with aP or wP.