Effectiveness of serogroup C meningococcal conjugate vaccine: a 7-year follow-up in Quebec, Canada.

Background: A mass immunization campaign was implemented in 2001 to control a serogroup C meningococcal disease outbreak, and a newly licensed serogroup C meningococcal conjugate vaccine (C-MCV) was used. In 2002, 1 C-MCV dose was routinely offered to children 12 months of age.

Objective: To assess the epidemiologic effect of the campaign and C-MCV effectiveness during a 7-year period according to age at vaccination and delay since vaccine administration.

Methods: Cases of invasive meningococcal infection reported to public health authorities and the reference laboratory during the period 1990 to 2008 were obtained to calculate year- and age-specific incidence rates. Multiple sources were used to ascertain the immunization status of cases. Immunization registry data were used to estimate age-specific C-MCV uptake rates in different birth cohorts. Vaccine effectiveness was estimated by Mantel-Haenszel method and logistic regression models.

Results: After mass immunization campaign, meningococcal C disease incidence decreased markedly not only in highly vaccinated but also in poorly vaccinated and nonvaccinated birth cohorts. Overall vaccine effectiveness was 87.4% (95% CI: 75.4%-94.2%) with lower protection in children vaccinated <2 years of age and waning of protection of higher magnitude in this age group.

Conclusions: Results support the current Canadian recommendation to provide booster vaccination for adolescents.