Evaluation of anti-Pertussis antibody levels in Iranian infants and children: Is it time to include booster acellular Pertussis Vaccines in the immunization schedule?

Introduction: The prevalence of anti-pertussis antibodies among infants and children in Iran has not been thoroughly investigated. Given that recommendations for booster vaccines are based on national disease epidemiology, we aimed to evaluate the seroprevalence of pertussis antibodies among infants and children in an Iranian referral hospital. Materials and methods: A total of 1012 infants and children were included in the study. Serum samples were stored at -20 degrees C until analysis. Demographic characteristics of patients, including age, sex, trivalent diphtheria, tetanus, and whole-cell pertussis (DTwP) vaccination status, and time since DTwP vaccination were collected. Anti-pertussis IgG antibodies were measured using a commercial ELISA kit. Results: In this cross-sectional study, the median age of the participants was 35 months (IQR:9-72 months). In infants <= 2 months, only 15 % had positive anti-pertussis antibodies. This increased to 28 % in the 3 to 4 months group and 55 % in the 5 to 6 months group. The highest positivity rates (63 % and 66 %) were seen in the 7 to 18 months and 19 to 36 months age groups, respectively. Positivity declined to 45 % in the 37 to 72 months group, and 47 % in those over 72 months. A significant relationship was found between the time elapsed since vaccination and anti-pertussis IgG levels (p = 0.005). Conclusion: Our study highlights a concerning prevalence of low anti-pertussis, especially among infants aged <= 2 months, where the majority displayed negative results. This situation underscores the vulnerability of newborns to pertussis due to insufficient immunity and emphasizes the urgent need for effective maternal vaccination strategies. Additionally, we observed a decline in anti-pertussis IgG levels after 36 months, raising concerns about waning immunity in older children. Continued research is crucial to evaluate the long-term efficacy of booster vaccines and to develop optimal vaccination strategies to protect infants and children from pertussis.