[The long controversy over anti-tuberculosis vaccination in Canada: the Calmette-Guerin bacillus (BCG), 1925-1975]

Association Between Bacillus Calmette-Guérin Vaccination and Childhood Asthma in the Quebec Birth Cohort on Immunity and Health

We estimated the association between bacillus Calmette-Guérin (BCG) vaccination and childhood asthma in a birth cohort using administrative databases, and we determined the impact of adjusting for potential confounders collected from a subset of the cohort members. Data were collected in 2 waves: 1) Administrative data for 76,623 individuals (stage 1) was gathered from the Quebec Birth Cohort on Immunity and Health (1974-1994), including BCG vaccination status, perinatal and sociodemographic characteristics, and use of health services for asthma; and 2) self-reported asthma risk factors were collected in 2012 by telephone interviews with 1,643 participants (stage 2) using a balanced 2-stage sampling design. We estimated odds ratios and 95% confidence intervals for asthma using logistic regression and correcting for the known sampling fractions from stage 1 to stage 2, overall and sex-stratified. In total, 35,612 (46.5%) individuals were BCG vaccinated, and 5,870 (7.7%) had asthma. The final odds ratio, integrating results from both stages of sampling, was 0.95 (95% confidence interval: 0.87, 1.04). Results did not differ according to sex (P for interaction = 0.327). To our knowledge, this is the largest study ever conducted on this topic, and using the best possible comprehensive adjustment for confounders, we found no association between BCG vaccination and asthma.

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 10-14years (7.9 per 100). The proportion of positive skin tests varied greatly by age, ranging from 10.2% among children <1year to 67.2% among adults ≥20years. 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 <1year (43.8 per 100) and 5-9year-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.

Assessment of factors associated with complete immunization coverage in children aged 12-23 months: a cross-sectional study in Nouna district, Burkina Faso

Background

The Expanded Program on Immunization (EPI) is still in need of improvement. In Burkina Faso in 2003, for example, the Nouna health district had an immunization coverage rate of 31.5%, compared to the national rate of 52%. This study identifies specific factors associated with immunization status in Nouna health district in order to advance improved intervention strategies in this district and in those with similar environmental and social contexts.

Methods

A cross-sectional study was undertaken in 41 rural communities and one semi-urban area (urban in the text). Data on 476 children aged 12 to 23 months were analyzed from a representative sample of 489, drawn from the Nouna Health Research Centre's Demographic Surveillance System (DSS) database. The vaccination history of these children was examined. The relationships between their immunization status and social, economic and various contextual variables associated with their parents and households were assessed using Chi square test, Pearson correlation and logistic regression.

Results

The total immunization coverage was 50.2% (CI, 45.71; 54.69). Parental knowledge of the preventive value of immunization was positively related to complete immunization status (p = 0.03) in rural areas. Children of parents who reported a perception of communication problems surrounding immunization had a lower immunization coverage rate (p < 0.001). No distance related difference exists in terms of complete immunization coverage within villages and between villages outside the site of the health centres. Children of non-educated fathers in rural areas have higher rates of complete immunization coverage than those in the urban area (p = 0.028). Good communication about immunization and the importance of availability of immunization booklets, as well as economic and religious factors appear to positively affect children's immunization status.

Conclusion

Vaccination sites in remote areas are intended to provide a greater opportunity for children to access vaccination services. These efforts, however, are often hampered by the poor economic conditions of households and insufficient communication and knowledge regarding immunization issues. While comprehensive communication may improve understanding about immunization, it is necessary that local interventions also take into account religious specificities and critical economic periods. Particular approaches that take into consideration these distinctions need to be applied in both rural and urban settings.

Abstract in French

See the full article online for a translation of this abstract in French.