Diphtheria in the United Kingdom: A Re-Emerging Public Health Challenge in the Post-Vaccination Era
Abstract
Diphtheria was considered one of the most significant causes of childhood morbidity and mortality worldwide in the pre-vaccine era that is caused by toxigenic strains of C. diphtheriae, C. ulcerans, or C. pseudotuberculosis. Diphtheria eventually become a rare disease in the UK due to a successful immunisation programme and sustained high vaccine coverage. However, an increase in reported diphtheria cases has been observed in recent years in the UK, even among vaccinated individuals. The aim of this study was to discuss and identify the potential causes of this re-emergence through summarising and analysing the data of diphtheria cases that have been reported in case reports, surveillance studies, and the UK routine surveillance. The findings indicated that epidemiological changes have occurred in the UK over the years. There was a considerable increase in NTCD isolates received by the NRL at PHE for confirmation and in notified NTCD diphtheria cases from (NOIDs). This review also found evidence of continued risk of C. ulcerans as an indigenous zoonotic pathogen related to companion animals, and result in several cases and deaths, particularly among older inadequately vaccinated populations. The significant and recent change was a large increase in cutaneous C. diphtheriae cases compared to C. ulcerans with a major risk of importing infection from endemic countries. This reappearance accompanied a shift in the age-distribution, with a higher tendency to occur in older adults due to the waning of childhood immunisation. Although several factors led to the resurgence of certain Corynebacterium species in different periods, this study supports recognition of unidentified cases rather than the re-emergence view due to the introduction of qPCR, increased case ascertainment following the former Soviet Union resurgence, and good surveillance in the country that has been reflected in detection of milder and atypical infections in fully or partially vaccinated individuals.