Meningococcal C vaccines: the Canadian experience.

BACKGROUND

Several outbreaks caused by virulent strains of serogroup C Neisseria meningitidis were observed in several Canadian provinces in the early 1990s. In an attempt to control these outbreaks, local immunization programs, with polysaccharide vaccines, directed at school age children and adolescents were initiated. In Quebec, however, the incidence of serogroup C meningococcal disease remained high among unvaccinated groups, and clusters appeared in previously unaffected areas. As a result, a 1-dose immunization campaign was initiated, targeting all 1.9 million people between 6 months and 20 years of age for vaccination with the polysaccharide vaccine. This campaign was effective in controlling the epidemic, but there was no evidence of vaccine effectiveness among children <2 years of age and protection was short-lived among older individuals. A second series of serogroup C meningococcal disease outbreaks were observed in several Canadian provinces from 1999 to 2001, and a mass immunization campaign with glycoconjugate vaccines against serogroup C meningococcal disease was implemented in the autumn of 2001.

METHODS

Evaluation of the effects of the glycoconjugate vaccination campaign was made with data on confirmed cases of serogroup C disease reported to the regional health authorities between January 1, 2001, and December 31, 2002. A cost effectiveness analysis of different glycoconjugate vaccine immunization strategies was also performed.

CONCLUSIONS

The 1999-2001 glycoconjugate vaccine mass immunization campaign was effective in reducing disease incidence among vaccinated and unvaccinated individuals. Results of the cost effectiveness study indicated that the most effective long term control strategy was a routine, 3-dose, infant vaccination program but the most cost-effective strategy was a routine 1-dose vaccination program in the setting of an acute outbreak.