Serological evaluation of immunity against Corynebacterium diphtheriae in the Peruvian adult population.

The reemergence of diphtheria outbreaks in Latin America calls for an assessment of the level of immune protection in adults. This study estimated IgG levels against Corynebacterium diphtheriae in individuals immunized and unimmunized with dT or DTaP boosters over the past 10 years. A cross-sectional study was conducted in 127 adults from Lima and Callao, divided according to recent vaccination history. Serum IgG levels were measured using an indirect ELISA (SERION ELISA® classic) and classified into four categories according to protection. The Mann-Whitney U test was used for comparative analysis. 26.8% showed no protection, while 62.2% showed certain or long-term protection. Among those vaccinated, 92.9% achieved protective levels, compared to 67.7% of those unvaccinated (p = .001). The 40-49 age group had the highest proportion of unprotected individuals (33.3%). Vaccination with dT or DTaP boosters was associated with protective IgG levels. A significant proportion of adults lacked immunity, especially among those who did not receive a booster, highlighting the need to strengthen immunization strategies in adults.