Efficacy of meningococcal vaccine and barriers to vaccination

Context.-Use of the quadrivalent meningococcal vaccine for control of outbreaks has increased in recent years, but the efficacy of meningococcal vaccine during mass vaccination campaigns in US civilian populations has not been assessed. Objectives.-To evaluate the efficacy of the quadrivalent meningococcal vaccine against serogroup C meningococcal disease in a community outbreak setting and to evaluate potentially modifiable barriers to vaccination in an area with persistent meningococcal disease following immunization. Design.-Matched case-control study of vaccine efficacy using cases of serogroup C meningococcal disease in persons eligible for vaccination during mass vaccination campaigns. Control patients were matched by neighborhood and age. The control group was used to identify possible barriers to vaccination. Setting.-Gregg County, Texas, population 106 076, from 1993 to 1995. Participants.-A total of 17 case patients with serogroup C meningococcal disease eligible for vaccine and 84 control patients. Main Outcome Measures.-Vaccine efficacy and risk factors associated with nonvaccination. Results.-Vaccine efficacy among 2- to 29-year-olds was 85% (95% confidence interval, 27%-97%) and did not change in bivariate analyses with other risk factors that were significant in univariate analysis. Among control patients, older age was strongly associated with nonvaccination; vaccination rates for 2- to 4-year-olds, 5- to 18-year-olds, and 19- to 29-year-olds were 67%, 48%, and 20%, respectively (chi(2) for linear trend, P=.01). Conclusions.-The meningococcal polysaccharide vaccine was effective against serogroup C meningococcal disease in this community outbreak. Although specific barriers to vaccination were not identified, older age was a risk factor for nonvaccination in the target population of 2- to 29-year-olds. In future outbreaks, emphasis should be placed on achieving high vaccination coverage, with special efforts to vaccinate young adults.