Early Estimate of the Effectiveness of Quadrivalent Meningococcal Conjugate Vaccine

Background: In January 2005, a quadrivalent meningococcal conjugate vaccine (MenACWY D) was licensed for use in the United States. The Advisory Committee on Immunization Practices recommends MenACWY D for all adolescents 11 to 18 years of age and others at increased risk for meningococcal disease. Methods: Reports of breakthrough meningococcal disease after vaccination with MenACWY D were collected. A simulation approach was used to estimate the expected number of cases in vaccinated persons. Results: Between 2005 and 2008, 14 breakthrough cases, including 3 deaths occurred. At a vaccine effectiveness (VE) of 90%, 7 breakthrough cases would be expected (range, 1-17); at VE of 85%, 11 cases (range, 2-30); at VE of 80%, 15 cases (range, 5-28); and at VE of 75%, 18 cases (range, 7-32) would be expected. The probability of the >= 14 observed cases occurring was 2.9% at VE of 90%, 29.3% at VE of 85%, 66.1% at VE of 80%, and 83.0% at VE of 75%. Conclusions: This report provides an early estimate of MenACWY D effectiveness within 3 to 4 years after vaccination, and suggests that MenACWY D effectiveness is 80% to 85%, similar to the VE reported for meningococcal polysaccharide vaccine.