The invasive Haemophilus influenzae type a (Hia) rate in the Sioux Lookout Meno Ya Win Health Centre (SLMHC) catchment area is 3.1/100,000/year.
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The SLMHC Hia rate exceeds the average rate of H. influenzae type b (Hib) for Canada in the pre-Hib vaccine era (1.76/100,000/year, range 0.92–2.98).
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Hia constituted 50% of H. influenzae cases from January 1, 2010 to June 30, 2015.
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SLMHC rates of invasive pneumococcal disease (IPD; 23.1/100,000/year) more closely resemble Canadian Arctic indigenous rates (38/100,000/year) compared to general Canadian rates (9.0/100,000/year).
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IPD and invasive H. influenzae rates are >2.5 times higher in Northwestern Ontario than in the general Canadian population.
Abstract
Introduction
North American indigenous populations experience a high burden of invasive bacterial infections. Because Streptococcus pneumoniae and Haemophilus influenzae have multiple antigenic variants, the existing vaccines cannot prevent all cases. This study addresses the current epidemiology of invasive H. influenzae and pneumococcal disease (IPD) in a region of Northwestern Ontario, Canada with a relatively high (82%) indigenous population.
Methods
Data were retrieved from a retrospective chart review at a hospital servicing a population of 29 000 (82% indigenous), during January 2010–July 2015.
Results
Ten cases of invasive H. influenzae disease and 37 cases of IPD were identified. The incidence of both in the study population (6.3 and 23.1/100 000/year, respectively) exceeded national rates (1.6 and 9.0/100 000/year). H. influenzae serotype a (Hia) was the most common (50%), followed by non-typeable H. influenzae (20%). In adults, 77% of IPD cases were caused by serotypes included in the 23-valent pneumococcal polysaccharide vaccine. All paediatric IPD cases were caused by serotypes not included in the 13-valent pneumococcal conjugate vaccine. The case-fatality rate was 10% for invasive H. influenzae and 2.7% for IPD. Most cases exhibited substantial co-morbidity.
Conclusions
In Northwestern Ontario, the incidence of invasive Hia disease exceeds that of H. influenzae type b (Hib) in the pre-Hib vaccine era. This provides strong support for the development of a new Hia vaccine. Improved pneumococcal vaccination of high-risk adults in the region is warranted.
