RESEARCH ARTICLE Effectiveness of Meningococcal C Conjugate Vaccine in Salvador, Brazil: A Case-Control Study

Background During a citywide epidemic of serogroup C meningococcal disease in Salvador in 2010, Brazil, the state government initiated mass vaccination targeting two age groups with high attack rates: individuals aged <5 years and 10–24 years. More than 600,000 doses of me-ningococcal serogroup C conjugate vaccines were administered. We performed a case-control study to evaluate vaccine uptake, document vaccine effectiveness and identify rea-sons for non-vaccination. Methods and Findings Population-based surveillance identified patients with laboratory-confirmed invasive meningo-coccal C (MenC) disease during 2010. Information onMenC vaccination was obtained from case patients and age-matched individuals from the same neighborhoods. MenC vaccine ef-fectiveness was estimated based on the exact odds ratios obtained by conditional logistic re-gression analysis. Of 51 laboratory-confirmed cases of serogroup Cmeningococcal disease among patients <5 and 10–24 years of age 50 were included in the study and matched with 240 controls. Overall case-fatality was 25%. MenC vaccine coverage among controls in-creased from 7.1 % to 70.2 % after initiation of the vaccination campaign. None of the 50 case patients but 70 (29.2%) of the 240 control individuals, including 59 (70.2%) of 84 matched with cases from the period after MenC vaccination, had received at least one MenC vaccine dose. Overall effectiveness of MenC was 98%with a lower 95 % exact confidence limit of 89%. Conclusions MenC vaccines administered during the meningococcal epidemic were highly effective, suggesting that rapid vaccine uptake through campaigns contributed to control of meningococcal disease