Serological evaluation of immunity against <i>Corynebacterium diphtheriae</i> 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 <i>Corynebacterium diphtheriae</i> 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.