Antitoxins for diphtheria and tetanus decline more slowly after vaccination with DTwP than with DTaP: a study in a Chinese population

Seroepidemiology of Tetanus among Healthy People Aged 1-59 Years Old in Shaanxi Province, China

The study aims to determine the seroprevalence of antibodies against tetanus among healthy people aged 1−59 years old in Shaanxi province. IgG against tetanus in serum samples were detected by ELISA. 6,439 subjects were enrolled. The positive rate (≥0.01 IU/mL) was 84.39% and GMC was 0.03 IU/mL. There were significant differences in positive rates (χ2 = 308.944, p < 0.01) and GMC (Z = 5,200,000, p < 0.01) among different age groups. The positive rates (χ2 = 304.3, p < 0.01) and GMCs (χ2 = 146.417, p < 0.01) showed regional differences. Both full protection rate (≥0.1 IU/mL) (χ2 = 36.834, p < 0.01) and GMC (Z = 688,000, p < 0.01) increased with the doses of tetanus-toxoid-containing vaccines (TTCVs) administered. The positive rate (χ2 = 54.136, p < 0.01) and GMC (Z = 140,200, p < 0.01) decreased gradually with the time interval after full immunization with TTCVs. The full protection rate (≥0.1 IU/mL) (χ2 = 176.201, p < 0.01) and GMC (Z = 629,900, p < 0.01) decreased with the interval (years) since the last dose of TTCVs. There were significant differences in the positive rates and GMCs for different ages, regions, immunization histories of TTCVs, and doses of TTCVs administered. The full protection rate and GMC decreased with the interval following full immunization with TTCVs and the interval since the last dose of TTCVs. The importance of using tetanus booster doses should be emphasized in adolescents and adults.

Bordetella pertussis in School-Age Children, Adolescents, and Adults: A Systematic Review of Epidemiology, Burden, and Mortality in Asia

Cyclic epidemics of pertussis (whooping cough) have been observed globally over the past twenty years despite high infant vaccine coverage. The resurgence of pertussis in high-income countries is partly due to waning vaccine immunity in older children and adults, as well as better surveillance and diagnostics. Moreover, in adolescents and adults, pertussis symptoms are mild and similar to common cough syndromes, meaning that it is under-diagnosed in older populations. A systematic search of MEDLINE, EMBASE, and BIOSIS was undertaken to identify studies published between 1 January 1990 and 17 June 2019, with information on pertussis epidemiology, burden of illness, and mortality in school-aged children, adolescents, and adults in Asia. Studies identified for inclusion were reviewed narratively because a statistical comparison was not possible due to the mix of methodologies used. The results showed that in East Asia, including Japan, South Korea, China, and Taiwan, pertussis is circulating in older children and adults. Diphtheria-tetanus-pertussis (DTP4) coverage is high in East Asia, yet outbreaks observed in Japan and South Korea suggest that vaccine-acquired immunity had waned in adolescents and adults. Several school outbreaks in China show that pertussis is circulating in young children, with continued circulation in adolescents and adults. There was a lack of information from Southeast/South Asian countries, although pan-Asian serosurveys showed that recent pertussis infection was common in adolescents and in adults with persistent cough. To conclude, the circulation of pertussis in Asian countries with high DTP4 coverage supports the expansion of routine vaccination to include booster doses for children at school entry and adolescents. However, surveillance is weak or absent in many countries, meaning that the true burden of pertussis, particularly among older populations, is unknown.

Efficacy, safety, and formulation issues of the combined vaccines

Introduction: Controlling the preventable infectious diseases is the main goal of vaccination. Among the vaccines, combined vaccines are of great importance for their social, public health, and economic values. It is stated that the combined vaccines are as efficient and safe as the monovalent vaccines. However, a concern has raised about the efficacy and safety of the combined vaccines due to the outbreaks of vaccine-preventable diseases and occurrence of serious adverse events. Areas covered: A retrospective literature search was conducted in the Google Scholar and PubMed databases to evaluate the efficacy and safety of the combined vaccines from 1980 to 2020 using appropriate keywords. Expert opinion: Several studies have shown efficacy and safety issues related to the combined vaccines. Different factors contribute to the inefficacy and lack of safety in the vaccines including formulation problems, limited data in the pre-licensure studies and challenges related to imperfection of the post-licensure surveillance systems. For surmounting the mentioned obstacles, there is a need to provide new formulations of the vaccines, revise the vaccines҆ safety and efficacy acceptance standards in the pre-licensure studies, improvement of post-licensure surveillance systems, and education of healthcare staff.

The Immunogenicity of the C Fragment of Tetanus Neurotoxin in Production of Tetanus Antitoxin

The demand of tetanus antitoxin (TAT) as tetanus treatment in developing and underdeveloped countries is still great since it is relatively easy to achieve and affordable. However, there are still issues in the preparation of highly effective TAT with tetanus toxoid (TT) as the immunogen. The tetanus toxin native C-fragment (TeNT-Hc) retains many properties and it is a very promising candidate for the development of tetanus human vaccine. In this study, we tested the immunogenicity of TeNT-Hc in the preparation of tetanus antibodies, by TeNT-Hc alone or in different combinations with TT. The antibody titers and components in horse serum or plasma in different groups were analyzed and compared with those immunized by the conventional TT and it showed comparability with the results of traditional methods. The plasma efficacy and in vivo tetanus toxin neutralization were also tested. After two stages of immunizations, the average potency in plasma of all groups reached more than 1,000 IU / mL except that in group 4. In group 5, the first two basic immunizations with TT and the subsequent immunizations with TeNT-Hc, it showed slightly higher antibody titers and potency. This study demonstrated that TeNT-Hc is a safe, effective, and yet easy-to-produce low-cost immunogen and suitable for TT replacement in tetanus antitoxin production.

Mathematical modeling of diphtheria transmission in Thailand

In this work, a mathematical model for describing diphtheria transmission in Thailand is proposed. Based on the course of diphtheria infection, the population is divided into 8 epidemiological classes, namely, susceptible, symptomatic infectious, asymptomatic infectious, carrier with full natural-acquired immunity, carrier with partial natural-acquired immunity, individual with full vaccine-induced immunity, and individual with partial vaccine-induced immunity. Parameter values in the model were either directly obtained from the literature, estimated from available data, or estimated by means of sensitivity analysis. Numerical solutions show that our model can correctly describe the decreasing trend of diphtheria cases in Thailand during the years 1977-2014. Furthermore, despite Thailand having high DTP vaccine coverage, our model predicts that there will be diphtheria outbreaks after the year 2014 due to waning immunity. Our model also suggests that providing booster doses to some susceptible individuals and those with partial immunity every 10 years is a potential way to inhibit future diphtheria outbreaks.

Factors contributing to the immunogenicity of meningococcal conjugate vaccines

Various glycoprotein conjugate vaccines have been developed for the prevention of invasive meningococcal disease, having significant advantages over pure polysaccharide vaccines. One of the most important features of the conjugate vaccines is the induction of a T-cell dependent immune response, which enables both the induction of immune memory and a booster response after repeated immunization. The nature of the carrier protein to which the polysaccharides are chemically linked, is often regarded as the main component of the vaccine in determining its immunogenicity. However, other factors can have a significant impact on the vaccine's profile. In this review, we explore the physico-chemical properties of meningococcal conjugate vaccines, which can significantly contribute to the vaccine's immunogenicity. We demonstrate that the carrier is not the sole determining factor of the vaccine's profile, but, moreover, that the conjugate vaccine's immunogenicity is the result of multiple physico-chemical structures and characteristics.

Acellular pertussis vaccines and pertussis resurgence: revise or replace?

The resurgence of pertussis (whooping cough) in countries with high vaccination coverage is alarming and invites reconsideration of the use of current acellular pertussis (aP) vaccines, which have largely replaced the old, reactogenic, whole-cell pertussis (wP) vaccine. Some drawbacks of these vaccines in terms of limited antigenic composition and early waning of antibody levels could be anticipated by the results of in-trial or postlicensure human investigations of B- and T-cell responses in aP versus wP vaccine recipients or unvaccinated, infected children. Recent data in experimental models, including primates, suggest that generation of vaccines capable of a potent, though regulated, stimulation of innate immunity driving effective, persistent adaptive immune responses against Bordetella pertussis infection should be privileged. Adjuvants that skew Th1/Th17 responses or new wP (detoxified or attenuated) vaccines should be explored. Nonetheless, the high merits of the current aP vaccines in persuading people to resume vaccination against pertussis should not be forgotten.