Bacillus Calmette-Guérin (BCG) vaccination patterns in the province of Québec, Canada, 1956–1974
Background: In the province of Québec, Canada, the Bacillus Calmette-Guérin (BCG) vaccine was offered to newborns and school-age children from the 1950s to mid-1970s in an organized tuberculosis prevention program. Objective: We aimed to describe the annual rates of skin test administration, proportion of skin tests that were positive, and rates of BCG vaccination from 1956 to 1974 according to age, sex, and administrative region. Methods: For rates, numerators were extracted from the Québec BCG Vaccination Registry whereas population denominators were obtained from the Canadian Census and governmental publications. Time trends were assessed with linear regression. Results: A total of 2,755,336 skin tests and 2,531,366 BCG vaccinations were administered. Yearly rates of skin tests, routinely administered before vaccination among all except newborns, were highest among children aged 5–9 (9.3 per 100) and 10–14 years (7.9 per 100). The proportion of positive skin tests varied greatly by age, ranging from 10.2% among children <1 year to 67.2% among adults ≥20 years. The vast majority of individuals who had a negative skin test were subsequently vaccinated, whereas those with a positive result were not, as per recommended guidelines. The average annual vaccination rate was highest among children aged <1 year (43.8 per 100) and 5–9 year-olds (6.9 per 100). There were salient differences in immunization rates, including positive skin tests and vaccinations, across administrative regions but no difference by sex. Conclusion: This is the first comprehensive description of the tuberculosis prevention program in Québec which offered free, non-mandatory BCG vaccination. Our results confirm that the targeted groups, newborns and school-age children, were preferentially reached. Socioeconomic, demographic, and organizational factors may explain regional differences in immunization rates. Beyond presenting a historical context for this vaccination campaign, our findings are relevant to contemporary uses of the Québec BCG Vaccination Registry in epidemiological research.