Researchers are racing to find effective therapies for coronavirus disease 2019 (COVID-19), which has resulted in a global pandemic.

That’s why Brown University Warren Alpert Medical School–led researchers looked at Bacillus Calmette-Guérin (BCG) vaccine, a live-attenuated strain derived from an isolate of Mycobacterium bovis and originally designed to prevent tuberculosis. Their report in Epidemiology and Infection says that the vaccine, has shown some efficacy against infection with unrelated pathogens. 

For their study, the authors reviewed medical records for 120 consecutive adult patients with COVID-19 at a major federally qualified health center in Rhode Island from March 19 to April 29, 2020. 

The patients’ median age was 39.5 years (interquartile range, 27.0-50.0), 30% were male, and 87.5% were Latino/Hispanic. Of those, 68.3%, had a history of BCG vaccination. 

Results indicate that individuals with BCG vaccination were less likely to require hospital admission during the disease course (3.7% vs. 15.8%, P = 0.019). “This association remained unchanged after adjusting for demographics and comorbidities (P = 0.017) using multivariate regression analysis,” the researchers explain. “The finding from our study suggests the potential of BCG in preventing more severe COVID-19.”

The study notes that patients with BCG vaccination were more likely to experience myalgia and less likely to require hospital admission. Researchers posit that myalgias might be related to the release of inflammatory mediators, such as interleukins (ILs).

“BCG is known to elicit non-specific immune effects through the induction of the innate immune responses and the enhanced production of IL-1Beta,” they write. “This may present as myalgias and help the body fight the infection.”

The authors add that recent ecological studies comparing countries with and without universal BCG vaccination policies suggest that BCG vaccination can significantly reduce mortality associated with COVID-19 and that mandatory BCG vaccination appeared to play a role in the flattening of the curve in the spread of COVID-19.

“These studies suggest a long-lasting protection conferred by childhood BCG vaccination against COVID-19,” according to the study authors. “This duration of protection may persist for several years, as one study examining BCG vaccine protection against tuberculosis found a 50–60 year duration of protection. A recent population-based study examining the cohort of Israeli adults aged 35–41 years found that the BCG vaccine may not reduce the likelihood of acquiring SARS-CoV-2 (difference, 1.3%; 95% CI –0.3% to 2.9%; P = 0.09). However, the lower hospitalization rate among BCG-vaccinated patients from our prospective cohort study suggests the potential of BCG in preventing more severe COVID-19 among those who acquired SARS-CoV-2.”

The authors say that their study was limited by a small sample size, short study time frame, unknown BCG strain each patient received, unknown BCG booster status, a preponderance of female patients, and a predominately Latino/Hispanic population. They call for future studies to explore the efficacy of BCG vaccination in preventing COVID-19 disease progression.

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