Meningococcal Conjugate Vaccine Failures in the United States: January 2005 to September 2008

Background:
In 2005, a tetravalent meningococcal conjugate vaccine (MCV4) was licensed for use in the United States. The Advisory Committee on Immunization Practices (ACIP) recommends MCV4 for adolescents aged 11-19 years, and others at increased risk for meningococcal disease.

Objectives:
To determine the number of MCV4 failures, and to identify common epidemiologic characteristics.

Methods:
A vaccine failure was defined as isolation of Neisseria meningitidis (serogroup A, C, Y, or W-135) from a clinical specimen taken from a normally sterile site, ≥10 days after vaccination with MCV4. Reports of vaccine failures were collected from Active Bacterial Core Surveillance (ABCs) and MeningNet sites participating in a MCV4 vaccine effectiveness evaluation, and from the Vaccine Adverse Events Reporting System (VAERS). ABCs and MeningNet sites cover 43% of the United States population.

Results:
Twelve vaccine failures were identified. Eleven were reported by ABCs or MeningNet sites, and one was reported through VAERS only. Seven cases were serogroup C, and five were serogroup Y. Subjects with vaccine failure presented a median of 339 days after vaccination (range, 93-1,021 days). Eleven cases were hospitalized; the median hospitalization time was four days (range, 0-14 days). There were three fatal cases; the case-fatality ratio was 25.0%. The mean age at the time of disease was 19.6 years (range, 15.2-24.9 years). One subject had a confirmed underlying complement deficiency. Each subject received vaccine from a different lot.

Conclusions:
Epidemiologic and vaccine lot analyses suggest no identifiable association among the 12 vaccine failures occurring since MCV4 licensure. Outside ABCs and MeningNet sites, reports of vaccine failures were collected through VAERS, a passive reporting system not designed for this purpose. Therefore, this analysis may underestimate the true number of vaccine failures in the United States. Inferences about MCV4 effectiveness cannot be made based on this analysis. Effectiveness studies are currently underway.