1. The overall effectiveness of the meningococcal conjugate vaccine between 0 and 8 years post-vaccination was 69%.
2. The vaccine effectiveness (VE) was 79% at <1 year from vaccination, 69% at 1 to 3 years from vaccination, and 61% at 3 to 8 years from vaccination.
Evidence Rating Level: 3 (Fair)
Study Rundown: Being that the incidence of meningitis in the pediatric population has decreased significantly with the advent of the meningococcal conjugate vaccine, vaccine researchers use serological markers, rather than clinical symptoms, to document immunity. Data from early studies on VE of the meningococcal conjugated vaccine suggest that immunity may wane after several years of a single dose. This study aimed to examine VE and the duration of immunity of the meningococcal conjugate vaccine. Results demonstrated that the overall VE of a single dose of the vaccine was 69%, while the VE was 71% among adolescents with no underlying conditions. After the first year of vaccination, VE was 79%; at 1 to 3 years post-vaccination, VE was 69%; and 3 to 8 years post-vaccination, VE was 61%. Limitations of the study include a small sample size and possible reporting bias due to lack of verification of vaccination status. Nonetheless, this case-control study was critical, especially for immunization policymakers, and it was the data from this study that informed the policy decision to add a booster dose at the age of 16 years.
In-Depth [case-control study]: Cases of meningococcal disease were identified through Active Bacterial Core surveillance (a population and laboratory based surveillance system coordinated by the CDC to the Emerging Infections Program) and MeningNet sites (local health departments funded to conduct enhanced meningococcal disease surveillance through the CDC). Eligibility included adolescents living in a surveillance area ≥ 11 years of age and born after January 1, 1986, at the time of illness. Cases were enrolled from January 1, 2006 through August 31, 2013 and were defined as those from which Neisseria meningitidis was isolated. These isolates were serogrouped and sent to the CDC for confirmation with PCR. Controls were eligible if they were within 2 years of the case and lived in the state or surveillance site at the time of illness onset of the case. Within this time period, 320 adolescents were identified as cases, but only 181 enrolled. A total of 199 controls were enrolled, where one or more of these controls were match to a case patient. The overall VE of a single dose of meningococcal disease was 69% (95% CI: 51 to 80%). VE was 79% in the first year after vaccination (95% CI: 49% to 91%), 69% at 1 to 3 years post-vaccination (95% CI: 44% to 83%), and 61% at 3 to 8 years after vaccination (95% CI: 25% to 79%).
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