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

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 po...

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Bibliographic Details
Published in:Clinical infectious diseases 2021-05, Vol.72 (10), p.e501-e505
Main Authors: de Chaisemartin, Clément, de Chaisemartin, Luc
Format: Article
Language:English
Subjects:
BCG Vaccine
Cohort Studies
COVID-19 - prevention & control
Economics and Finance
Humanities and Social Sciences
Humans
Infant
Infant, Newborn
Middle Aged
Pandemics
SARS-CoV-2
Sweden - epidemiology
Vaccination
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Summary: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. 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. 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%. 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.
ISSN:1058-4838
1537-6591
DOI:10.1093/cid/ciaa1223