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

Abstract

BackgroundInvasive 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.MethodsWe 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).ResultsA 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.ConclusionsAlthough 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.

Enhanced surveillance of invasive meningococcal disease in Canada, 2006-2011

“…In the neighbouring province of Ontario, no similar increase of this strain or cases of disease have been observed (26,27). An unusual shift in the genotype of invasive meningococcal C strains has also been observed, from predominantly ET15 type to ET-37 (non-ET-15) type (28).…”

How and why researchers use the number needed to vaccinate to inform decision making—A systematic review

“…Two studies each focused on Hepatitis A [25,26] and pneumococcal disease [4,27]. Other disease outcomes included serogroup B meningococcal disease [28], respiratory syncytial virus (RSV) [29], and rabies [30]. Outcomes for which NNVs were measured included being a case of a specific disease, death, hospitalization, outpatient visit, qualityadjusted life year (QALY), disability-adjusted life year (DALY), and life-years lost.…”

Rapid surveillance for health events following a mass meningococcal B vaccine program in a university setting: A Canadian Immunization Research Network study

“…Case fatality rates range from 5.3% to 10.7%, long term morbidity occurs in up to one third of survivors, and public health and acute care resources are urgently diverted to handle real and suspected cases [1][2][3]. Since the successful introduction of universal meningococcal C vaccine programs in Canada beginning in 2001, serotype B disease is the most common cause of invasive meningococcal disease (IMD).…”