Incidence of Tetanus and Diphtheria in Relation to Adult Vaccination Schedules.

BACKGROUND: The World Health Organization (WHO) does not recommend routine adult booster vaccination for tetanus and diphtheria after completion of the childhood vaccination series. However, many countries continue to implement adult booster vaccinations, leading to the question of whether this is necessary to reduce the incidence of these 2 rare diseases. METHODS: We conducted an observational cohort study based on WHO case reports from 2001 through 2016. We compared the incidence of tetanus and diphtheria in 31 North American and European countries that either do or do not recommend adult booster vaccination. RESULTS: Countries that vaccinate adults every 5-20 years (group 1) were compared with countries that do not routinely vaccinate adults for tetanus or diphtheria (group 2). Comparison of group 1 vs group 2 revealed no significant decline in tetanus incidence rates among countries that vaccinate adults (P = .52; risk ratio [RR] = 0.78; 95% confidence interval [CI], .36 to 1.70). The risk of contracting diphtheria was increased among countries that vaccinate adults due to inclusion of Latvia, a country that had poor vaccination coverage (P < .001). However, if Latvia is excluded, there is no difference in diphtheria incidence between countries that do or do not routinely vaccinate adults (P = .26; RR = 2.46; 95% CI, .54 to 11.23). CONCLUSIONS: Review of >11 billion person-years of incidence data revealed no benefit associated with performing adult booster vaccinations against tetanus or diphtheria. Similar to other vaccines, this analysis supports the WHO position on adult booster vaccination and, if approved by governing health authorities, this may allow more countries to focus healthcare resources on vulnerable and undervaccinated populations.

Active Circulation of Corynebacterium ulcerans among Nonhuman Primates.

Diphtheria is rare in the United States. and many industrialized nations due to development of an effective vaccine, coupled with high vaccination coverage. Although there is continued risk of importation and transmission of Corynebacterium diphtheriae, C. ulcerans has now become the dominant source of diphtheria cases among several European countries. Bearing this in mind, a better understanding of C. ulcerans biology is clearly needed. Here, we identified active transmission of toxigenic C. ulcerans among indoor- and outdoor-housed rhesus macaques based on diphtheria toxin-specific serology assays as well as direct isolation of C. ulcerans from a recently infected animal. In addition to animal-to-animal transmission, we found serological evidence indicative of potential human transmission. Together, these results provide new details on natural Corynebacterium transmission among nonhuman primates and emphasizes the importance of maintaining high vaccination coverage to reduce the risk of potential zoonotic infection. IMPORTANCE C. ulcerans represents an emerging zoonotic agent of diphtheria, but little is known about its transmission or maintenance among animal reservoirs. In these studies, we identified diphtheria outbreaks among both outdoor- and indoor-housed rhesus macaques and isolated a toxigenic strain of C. ulcerans from a recently infected animal. Retrospective analysis indicated that toxigenic Corynebacteria have been circulating among these primates for decades with the potential for rare zoonotic transmission to humans.

Pre-clinical development of a hydrogen peroxide-inactivated West Nile virus vaccine.

West Nile virus (WNV) is a mosquito-transmitted pathogen with a wide geographical range that can lead to long-term disability and death in some cases. Despite the public health risk posed by WNV, including an estimated 3 million infections in the United States alone, no vaccine is available for use in humans. Here, we present a scaled manufacturing approach for production of a hydrogen peroxide-inactivated whole virion WNV vaccine, termed HydroVax-001WNV. Vaccination resulted in robust virus-specific neutralizing antibody responses and protection against WNV-associated mortality in mice or viremia in rhesus macaques (RM). A GLP-compliant toxicology study performed in rats demonstrated an excellent safety profile with clinical findings limited to minor and transient irritation at the injection site. An in vitro relative potency (IVRP) assay was developed and shown to correlate with in vivo responses following forced degradation studies. Long-term in vivo potency comparisons between the intended storage condition (2-8°C) and a thermally stressed condition (40±2°C) demonstrated no loss in vaccine efficacy or protective immunity over a 6-month span of time. Together, the positive pre-clinical findings regarding immunogenicity, safety, and stability indicate that HydroVax-001WNV is a promising vaccine candidate.