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

eScholarship, University of California 2021-05-01

BackgroundThe 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.MethodsNumbers 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.ResultsThe 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%.ConclusionsWhile 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.

Humans; BCG Vaccine; Vaccination; Cohort Studies; Middle Aged; Infant; Newborn; Sweden; Pandemics; COVID-19; SARS-CoV-2; BCG; regression discontinuity; Covid-19; Regression discontinuity; Microbiology; Biological Sciences; Medical and Health Sciences; article

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Clinical infectious diseases : an official publication of the Infectious Diseases Society of America vol 72, iss 10, e501-e505 1058-4838

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