Of possible interest. Complicated story.
https://www.pnas.org/content/pnas/early/2020/07/07/2008410117.full.pdf
Luis E. Escobara,1, Alvaro Molina-Cruzb, and Carolina Barillas-Muryb,1
aDepartment of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, VA 24601; and bLaboratory of Malaria and
Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892 Contributed by Carolina Barillas-Mury, June 9, 2020 (sent for review May 1, 2020; reviewed by Serap Aksoy and Rita R. Colwell)
A series of epidemiological explorations has suggested a negative association between national bacillus Calmette–Guérin (BCG) vac- cination policy and the prevalence and mortality of coronavirus disease 2019 (COVID-19). However, these comparisons are difficult to validate due to broad differences between countries such as socioeconomic status, demographic structure, rural vs. urban set- tings, time of arrival of the pandemic, number of diagnostic tests and criteria for testing, and national control strategies to limit the spread of COVID-19. We review evidence for a potential biological basis of BCG cross-protection from severe COVID-19, and refine the epidemiological analysis to mitigate effects of potentially con- founding factors (e.g., stage of the COVID-19 epidemic, develop- ment, rurality, population density, and age structure). A strong correlation between the BCG index, an estimation of the degree of universal BCG vaccination deployment in a country, and COVID- 19 mortality in different socially similar European countries was observed (r2 = 0.88; P = 8 × 10−7), indicating that every 10% in- crease in the BCG index was associated with a 10.4% reduction in COVID-19 mortality. Results fail to confirm the null hypothesis of no association between BCG vaccination and COVID-19 mortality, and suggest that BCG could have a protective effect. Nevertheless, the analyses are restricted to coarse-scale signals and should be considered with caution. BCG vaccination clinical trials are required to corroborate the patterns detected here, and to establish causal- ity between BCG vaccination and protection from severe COVID- 19. Public health implications of a plausible BCG cross-protection from severe COVID-19 are discussed.
BCG vaccination policy | COVID-19 coronavirus | cross-protection | mortality | pandemic
