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Epidemiol Health > Volume 43; 2021 > Article
Epidemiology and Health 2021;43: e2021060-0.
DOI: https://doi.org/10.4178/epih.e2021060    Published online Sep 8, 2021.
Bacillus of Calmette and Guérin (BCG) and the risk of leprosy in Ciudad del Este, Paraguay, 2016-2017
Nancy Carolina Cuevas1  , Victor M. Cardenas2 
1Alto Paraná District, Ministry of Health, Ciudad del Este, Paraguay, USA
2Department of Epidemiology, Fay W. Boozman College of Public Health, University of Arkansas for Medical Sciences, Little Rock, AR, USA
Correspondence  Victor M. Cardenas ,Email: cardenasvictor08@gmail.com
Received: Jul 15, 2021  Accepted after revision: Sep 8, 2021
Paraguay has experienced a 35% reduction in the detected incidence of leprosy during the last ten years, as the vaccination coverage against tuberculosis (Bacillus of Calmette and Guérin [BCG] vaccine) reached ≥95% among infants. The objective of this case-control study was to evaluate the protective effect of BCG on the risk of leprosy.
We used a population-based case-control study of 20 leprosy confirmed cases reported among residents of Ciudad del Este, Paraguay, diagnosed in 2016-2017. Three controls were selected from a random sample of households from the city. We assessed vaccine effectiveness using 1- odds ratio [OR], and confounding for age, gender, education, occupation, and marital status using stratified and exact logistic regression, and explored if there was effect modification calculating the synergy factor (SF) and relative excess risk due to interaction (RERI).
After controlling for age, gender, education, occupation and marital status, the OR of BCG scar on the risk of leprosy was 0.10 (95% confidence interval [CI], 0.02 to 0.45), for an estimate of vaccine effectiveness of 89.5% reduced risk of leprosy (95% CI, 55.2 to 98.1). There was evidence of heterogeneity by which the effectiveness of BCG seemed stronger among younger persons (Breslow-Day and Z-test of the SF had a p<0.05), and both the RERI and SF indicated a less then multiplicative and additive interaction of BCG and younger age.
BCG vaccination was associated with a decreased risk of leprosy in the study population, particularly in persons born after 1980.
Keywords: Leprosy, BCG vaccine, Case-control studies, Epidemiologic studies, Prevention and control, Paraguay
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