Epidemiological study of hepatitis B virus infection in Manitoba, Canada, 1992–2003

In comparison with other Canadian provinces and most Western countries, the province of Manitoba maintains a different vaccination policy for hepatitis B. This policy provides selective antenatal screening for hepatitis B in women and an inoculation program for hepatitis B vaccination for fourth-grade pupils. There has been increasing concern for this policy with regard to its influence on secular trends of acute hepatitis B incidence in Manitoba. This created a need to summarise the epidemiological characteristics of hepatitis B virus (HBV) infection in Manitoba and to allocate finances and human resources for future prevention programs. The Cadham Provincial Laboratory in Winnipeg, a Canadian Public Health Laboratory, is responsible for testing all specimens for diagnosis of various common infectious diseases in Manitoba. During the period from 1 January 1992 to 31 December 2003, a total of 285,946 clinical specimens were submitted to this laboratory, which confirmed 310 cases of acute HBV and 7,556 cases of chronic HBV infection. A total of 18,168 individuals were identified as having vaccine-induced immune status. The incidence rate of acute HBV infection has significantly decreased from 6.52/100,000 person-years in 1996 to 0.86/100,000 person-years in 2003. Annual prevalence rates of chronic HBV infection in Manitoba increased slightly from 42.96 cases/100,000 population in 1992 to 71.47 cases/100,000 population in 2003. Incidence rates were generally higher in men than in women at all age groups, with values of 2.65 and 1.65 per 100,000 population, respectively (chi-square=15.768, p value <0.001). The highest incidence rate for both males and females was observed in the age group 30–34 years. The North Eastman and Winnipeg Regional Health Authorities showed significantly higher incidence rates of acute hepatitis B compared with the other nine Regional Health Authorities. Selective hepatitis B vaccination programs for children in Manitoba had achieved the greatest success in the prevention of vertical and horizontal transmission. There is an urgent need to develop cost-effective harm-reduction strategies for hepatitis B prevention among adults (aged 30–34) and groups at risk in Manitoba.