Background: To assess antibody titers afforded by meningococcal C- (MenC) tetanus toxoid conjugate vaccine at 12 months of age in three different immunization schedules.
Methods: This prospective study included three similar cohorts of healthy infants from 1-dose, 2-dose and 3-dose MenC infant immunization programs. Infants were enrolled at 12 months of age and given the final scheduled dose of MenC-tetanus toxoid conjugate vaccine with sera collected prior to and 1 month after the vaccination. Serum bactericidal activity (SBA) titers ≥ 1:8 were considered protective.
Results: Before the 12 month dose, participants had significantly different protective titers according to the number of prior doses received: 100% (95% CI 97.6-100%) of infants who had 2 prior doses (at 2 and 4 months) were protected compared to 84.0% (76.7-89.3%) of participants with one dose (at 2 months) and 27.6% (21.0-35.4%) of unvaccinated infants. All subjects were protected after the 12 month MenC dose, but titers were higher with prior priming.
Conclusions: Two MenC doses given in infancy afford optimal protection during the first year of life; however, substantial protection was seen after one dose at 2 months.
Trial registration: ClinicalTrials.gov NCT00936962.
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