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.

CONCLUSION

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