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Open Access Highly Accessed Research article

Epidemiology of serogroup B invasive meningococcal disease in Ontario, Canada, 2000 to 2010

Vica Dang12, Frances B Jamieson13, Sarah Wilson12, Prasad Rawte1, Natasha S Crowcroft123, Karen Johnson1, Raymond S W Tsang4 and Shelley L Deeks12*

Author Affiliations

1 Public Health Ontario, Toronto, ON, Canada

2 Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada

3 Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada

4 National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada

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BMC Infectious Diseases 2012, 12:202  doi:10.1186/1471-2334-12-202

Published: 29 August 2012

Abstract

Background

Invasive meningococcal disease (IMD) caused by serogroup B is the last major serogroup in Canada to become vaccine-preventable. The anticipated availability of vaccines targeting this serogroup prompted an assessment of the epidemiology of serogroup B disease in Ontario, Canada.

Methods

We retrieved information on confirmed IMD cases reported to Ontario’s reportable disease database between January 1, 2000 and December 31, 2010 and probabilistically-linked these cases to Public Health Ontario Laboratory records. Rates were calculated with denominator data obtained from Statistics Canada. We calculated a crude number needed to vaccinate using the inverse of the infant (<1 year) age-specific incidence multiplied by expected vaccine efficacies between 70% and 80%, and assuming only direct protection (no herd effects).

Results

A total of 259 serogroup B IMD cases were identified in Ontario over the 11-year period. Serogroup B was the most common cause of IMD. Incidence ranged from 0.11 to 0.27/100,000/year, and fluctuated over time. Cases ranged in age from 13 days to 101 years; 21.4% occurred in infants, of which 72.7% were <6 months. Infants had the highest incidence (3.70/100,000). Case-fatality ratio was 10.7% overall. If we assume that all infant cases would be preventable by vaccination, we would need to vaccinate between 33,784 and 38,610 infants to prevent one case of disease.

Conclusions

Although rare, the proportion of IMD caused by serogroup B has increased and currently causes most IMD in Ontario, with infants having the highest risk of disease. Although serogroup B meningococcal vaccines are highly anticipated, our findings suggest that decisions regarding publicly funding serogroup B meningococcal vaccines will be difficult and may not be based on disease burden alone.

Keywords:
Invasive meningococcal disease; Neisseria meningitidis; Serogroup B; Epidemiology; Surveillance; Ontario; Canada