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. 2021 Dec 8;39(50):7300-7307.
doi: 10.1016/j.vaccine.2021.08.019. Epub 2021 Aug 11.

Does BCG provide long-term protection against SARS-CoV-2 infection? A case-control study in Quebec, Canada

Jacques Pépin  1 , Annie-Claude Labbé  2 , Alex Carignan  1 , Marie-Elise Parent  3 , Jennifer Yu  3 , Cynthia Grenier  1 , Stéphanie Beauchemin  4 , Philippe De Wals  5 , Louis Valiquette  1 , Marie-Claude Rousseau  6
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Does BCG provide long-term protection against SARS-CoV-2 infection? A case-control study in Quebec, Canada

Jacques Pépin et al. Vaccine. .

Abstract

Background: Early in the coronavirus disease 2019 (COVID-19) pandemic, before severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines became available, it was hypothesized that BCG (Bacillus Calmette-Guérin), which stimulates innate immunity, could provide protection against SARS-CoV-2. Numerous ecological studies, plagued by methodological deficiencies, revealed a country-level association between BCG use and lower COVID-19 incidence and mortality. We aimed to determine whether BCG administered in early life decreased the risk of SARS-CoV-2 infection in adulthood and the severity of COVID-19.

Methods: This case-control study was conducted in Quebec, Canada. Cases were patients with a positive SARS-CoV-2 nucleic acid amplification test performed at two hospitals between March-October 2020. Controls were identified among patients with non-COVID-19 samples processed by the same microbiology laboratories during the same period. Enrolment was limited to individuals born in Quebec between 1956 and 1976, whose vaccine status was accessible in a computerized registry of 4.2 million BCG vaccinations.

Results: We recruited 920 cases and 2123 controls. Fifty-four percent of cases (n = 424) and 53% of controls (n = 1127) had received BCG during childhood (OR: 1.03; 95% CI: 0.89-1.21), while 12% of cases (n = 114) and 11% of controls (n = 235) had received two or more BCG doses (OR: 1.14; 95% CI: 0.88-1.46). After adjusting for age, sex, material deprivation, recruiting hospital and occupation there was no evidence of protection conferred by BCG against SARS-CoV-2 (AOR: 1.01; 95% CI: 0.84-1.21). Among cases, 77 (8.4%) needed hospitalization and 18 (2.0%) died. The vaccinated were as likely as the unvaccinated to require hospitalization (AOR: 1.01, 95% CI: 0.62-1.67) or to die (AOR: 0.85, 95% CI: 0.32-2.39).

Conclusions: BCG does not provide long-term protection against symptomatic COVID-19 or severe forms of the disease.

Keywords: BCG; COVID-19; SARS-CoV-2; Vaccine effectiveness.

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Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Study sample profile.
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