Meningococcal C Conjugate Vaccine Reduces Meningitis Rates in Canada

Rates of meningitis have decreased in Canadian provinces introducing routine immunization of children and adolescents against one specific strain of meningococcal bacteria, reports a study in the March issue of The Pediatric Infectious Disease Journal. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health, a leading provider of information and business intelligence for students, professionals, and institutions in medicine, nursing, allied health, pharmacy and the pharmaceutical industry.

Rates of meningitis due to Neisseria meningitidis serogroup C decreased dramatically in provinces where the childhood meningococcal serogroup C conjugate (MenC) vaccine was first introduced, according to the new report. The lead author was Julie A. Bettinger, Ph.D., M.P.H., of the University of British Columbia, Vancouver.

The Canadian Immunization Monitoring Program, Active (IMPACT) network, along with local public health officials, investigated the effects of the MenC vaccine. Two provinces, Quebec and Alberta, introduced immunization with MenC vaccine for children and adolescents in 2002. Meningitis is caused by five major strains of meningococcal bacteria; in North America, most outbreaks of meningitis are caused by serogroup C.

Other provinces introduced the MenC vaccine in later years. "The staggered implementation of universal childhood MenC immunization programs across Canada provides an opportunity to evaluate their influence, while controlling for natural variation," Dr. Bettinger and colleagues write.

Sharp Drop in Serogroup C Meningitis after MenC Vaccination

The IMPACT surveillance program, covering over half of the Canadian population, identified 376 cases of meningitis over the five years studied. The yearly number of cases decreased from 96 in 2002 to 68 in 2006. About nine percent of the patients died.

The rate of meningitis was highest in children aged 0 to 4 and in adolescents aged 15 to 19. From 2002 to 2006, the overall incidence of meningitis decreased by about half in both age groups.

Most of the change resulted from reductions in cases of serogroup C meningitis, which decreased by 65 percent. At the same time, the rate of meningitis caused by other serogroups was unchanged. This means that there was no "serogroup replacement"—increases in other types of meningitis offsetting the reductions in serogroup C disease.

"[W]e found that the decrease in serogroup C incidence was primarily the result of a substantial decrease in provinces that started earlier immunization programs," the researchers write. In those provinces, the rate of serogroup C disease decreased by more than 80 percent, compared to no change in provinces where MenC vaccination was introduced later.

The study also showed reductions in meningitis caused by serogroup C in adults, even though adults weren't routinely vaccinated. The reductions in adults probably resulted from "herd immunity"—the lower the number of infected individuals in the population, the lower the chances of transmitting the disease.