Serum Bactericidal Antibody Responses of Students Immunized with a Meningococcal Serogroup B Vaccine in Response to an Outbreak on a University Campus

Background MenB-4C is a recently licensed meningococcal serogroup B vaccine. For vaccine licensure, short-term efficacy was inferred from serum bactericidal antibody (SBA) titers against 3 antigen-specific indicator strains, which are not necessarily representative of US disease-causing strains. Methods A total of 4923 students were immunized with MenB-4C in response to an outbreak at a university. Serum samples were obtained at 1.5-2 months from 106 students who received the recommended 2 doses and 52 unvaccinated students. Follow-up serum samples were obtained at 7 months from 42 vaccinated and 24 unvaccinated participants. SBA was measured against strains from 4 university outbreaks. Results At 1.5-2 months, the proportion of immunized students with protective titers ≥1:4 against an isolate from the campus outbreak was 93% (95% confidence interval [CI], 87%-97%) vs 37% (95% CI, 24%-51%) in unvaccinated students. The proportion with protective titers against strains from 3 other university outbreaks was 73% (95% CI, 62%-82%) vs 26% (95% CI, 14%-41%) in unvaccinated; 71% (95% CI, 61%-79%) vs 19% (95% CI, 10%-33%) in unvaccinated; and 53% (95% CI, 42%-64%) vs 9% (95% CI, 3%-22%) in unvaccinated (P <.0001 for each strain). At 7 months, the proportion of immunized students with titers ≥1:4 was 86% (95% CI, 71%-95%) against the isolate from the campus outbreak and 57% (95% CI, 41%-72%), 38% (95% CI, 24%-54%), and 31% (95% CI, 18%-47%), respectively, for the other 3 outbreak strains. Conclusions MenB-4C elicited short-term protective titers against 4 strains responsible for recent university campus outbreaks. By 7 months the prevalence of protective titers was <40% for 2 of the 4 outbreak strains. A booster dose of MenB-4C may be needed to maintain protective titers.