Bacille Calmette-Guérin Vaccination in Infancy Does Not Protect Against Coronavirus Disease 2019 (COVID-19): Evidence From a Natural Experiment in Sweden

Clément de Chaisemartin and Luc de Chaisemartin
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Luc de Chaisemartin: AP-HP - Assistance publique - Hôpitaux de Paris (AP-HP), IT - INSERM-TRANSFERT [Paris] - INSERM - Institut National de la Santé et de la Recherche Médicale, AP-HP. Université Paris Saclay

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Abstract: Background The bacille Calmette-Guérin (BCG) tuberculosis vaccine has immunity benefits against respiratory infections. Accordingly, it has been hypothesized to have a protective effect against coronavirus disease 2019 (COVID-19). Recent research found that countries with universal BCG childhood vaccination policies tend to be less affected by the COVID-19 pandemic. However, such ecological studies are biased by numerous confounders. Instead, this paper reports on a rare nationwide natural experiment that occurred in Sweden in 1975, where discontinuation of newborns' BCG vaccination led to a dramatic decrease in BCG coverage rate, thus allowing us to estimate BCG's effect without the biases associated with cross-country comparisons. Methods Numbers of COVID-19 cases and hospitalizations were recorded for birth cohorts born just before and just after 1975, representing 1 026 304 and 1 018 544 individuals, respectively. We used regression discontinuity to assess the effect of BCG vaccination on COVID-19–related outcomes. On such a large population, this method allows for a precision that would be hard to achieve using a randomized controlled trial. Results The odds ratios (95% CI) for COVID-19 cases and COVID-19–related hospitalizations were 1.0005 (.8130–1.1881) and 1.2046 (.7532–1.6560), allowing us to reject fairly modest effects of universal BCG vaccination. We can reject with 95% confidence that universal BCG vaccination reduces the number of cases by 19% and the number of hospitalizations by 25%. Conclusions While the effect of a recent vaccination must be evaluated, we provide strong evidence that receiving the BCG vaccine at birth does not have a protective effect against COVID-19 among middle-aged individuals.

Keywords: COVID-19; BCG; Regression discontinuity (search for similar items in EconPapers)
Date: 2021-05-15
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Published in Clinical Infectious Diseases, 2021, 72 (10), pp.e501-e505. ⟨10.1093/cid/ciaa1223⟩

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Persistent link: https://EconPapers.repec.org/RePEc:hal:journl:hal-03948008

DOI: 10.1093/cid/ciaa1223

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