BCG vaccine does not reduce Covid-19 risk among healthcare workers: NEJM

A new study by Laure Pittet and team found that health care professionals who received the bacille Calmette-Guerin (BCG)-Denmark vaccine did not reduce the risk of Covid-19. The findings of this study were published in The New England Journal of Medicine.

It has been postulated that the immunomodulatory "off-target" effects of the bacille Calmette-Guérin (BCG) vaccination will provide defense against coronavirus disease 2019 (Covid-19). The BCG vaccination has been linked to a decreased risk of newborn death from any cause and a decreased risk of adolescent and adult respiratory illnesses. Therefore, the purpose of this study was to evaluate the effectiveness of the BCG vaccination against Covid-19 in healthcare practitioners.

The BCG-Denmark vaccination or a saline placebo was given to healthcare professionals in this multinational, double-blind, placebo-controlled experiment at random, and they were observed for 12 months. The primary analyses covered the modified intention-to-treat group, which was limited to people having a negative test for severe acute respiratory syndrome coronavirus 2 at baseline. Symptomatic Covid-19 and severe Covid-19, the primary outcomes, were examined at 6 months.

The key findings of this study were:

1. Randomization involved a total of 3988 people; because of the availability of Covid-19 vaccinations, enrollment ended before the intended sample size was attained.

2. 84.9% of the subjects who underwent randomization were included in the modified intention-to-treat population, with 1703 in the BCG group and 1683 in the placebo group.

3. By six months, the estimated probability of symptomatic Covid-19 in the BCG group was 14.7%, compared to 12.3% in the placebo group.

4. By six months, there was a 7.6% incidence of severe Covid-19 in the BCG group and a 6.5% risk in the placebo group; most people who fulfilled the trial's criterion of severe Covid-19 did not require hospitalization but were unable to work for at least three days straight.

5. Although the confidence intervals were smaller in the supplemental and sensitivity analyses that utilized less stringent censoring procedures, the risk differences remained similar.

6. Each cohort experienced five hospitalizations as a result of Covid-19, with the placebo group experiencing one fatality.

7. When comparing the BCG group to the placebo group, the hazard ratio for any Covid-19 incident was 1.23. There were no issues with regard to safety.

Reference:

Pittet, L. F., Messina, N. L., Orsini, F., Moore, C. L., Abruzzo, V., Barry, S., Bonnici, R., Bonten, M., Campbell, J., Croda, J., Dalcolmo, M., Gardiner, K., Gell, G., Jamieson, T., Jardim, B., … Curtis, N. (2023). Randomized Trial of BCG Vaccine to Protect against Covid-19 in Health Care Workers. In New England Journal of Medicine (Vol. 388, Issue 17, pp. 1582–1596). Massachusetts Medical Society. https://doi.org/10.1056/nejmoa2212616