Lack of seroprotection against diphtheria in the Austrian population, in light of reported diphtheria cases in Europe, 2022.

Following an increase in diphtheria cases in Europe since 2022, we retrospectively estimated the prevalence of seroprotection against diphtheria and tetanus in 10,247 Austrian residents (population: 8,978,929) voluntarily tested between 2018 and 2022. Lack of seroprotection against diphtheria was found in 36% compared with 4% against tetanus. The geometric mean antibody concentration against tetanus was 7.9-fold higher compared with that for diphtheria. Raising awareness of regular booster vaccinations against diphtheria in combination with tetanus and pertussis is urgently needed.