Widespread circulation of pertussis and poor protection against diphtheria among middle-aged adults in 18 European countries
Abstract Reported incidence of pertussis in member states of the European Union (EU) and the European Economic Area (EEA) varies and may not reflect the real situation. In the EU/EEA, vaccine-induced protection against diphtheria and tetanus seems sufficient as few cases are reported even among the adult population who was vaccinated many years ago. Aim of this study was to determine the seroprevalence of pertussis, diphtheria and tetanus antibodies in EU/EEA countries within the age groups of 40-49 and 50-59 years. Eighteen countries collected around 500 samples between 2015 and 2018 (N=10,302 in total) and they were analysed for IgG-specific antibodies against pertussis toxin (PT), diphtheria toxoid (Dt) and tetanus toxin (TT). The proportion of sera with IgG-PT antibody levels ≥100 IU/mL, indicative for recent pertussis infection was comparable for 13/18 countries ranging between 4.0-6.4%. For diphtheria the proportion of sera lacking the protective level (<0.1 IU/mL) varied between 22.8% and 82.0%. For tetanus the protection was sufficient: only very few sera showed unprotective IgG-TT antibody levels. The seroprevalence of pertussis indicates that the circulation of B. pertussis is widespread across EU/EEA. The lack of vaccine-induced seroprotection against diphtheria in EU/EEA in these age groups is of concern and deserves further attention.