Exercising caution in correlating COVID-19 incidence and mortality rates with BCG vaccination policies due to variable rates of SARS CoV-2 testing

Janine Hensel; Daniel J McGrail; Kathleen M McAndrews; Dara Dowlatshahi; Valerie S LeBleu; Raghu Kalluri

In most countries with high TB incidence, children receive the BCG vaccine in early infancy. These countries have implemented a universal BCG vaccination policy. In some of these countries, when TB incidence dropped, the policy was amended to stop universal BCG vaccination, and this group is categorized in this report as having universal BCG policy in the past. A few countries have never had a universal BCG policy. The reason for not vaccinating was due to low TB incidence and the possibility to retain use of the tuberculin skin test in order to assess current TB infections. In countries with active BCG vaccination programs, the variability in protection against TB could be due to differences in the BCG strains used in vaccine synthesis, vaccine batch differences, time of vaccination, previous exposure to mycobacterium, and distinct host haplotypes [4] . The BCG vaccine may offer protection for as long as 30 to 40 years post vaccination (as previously reported in Norway [5] ), and possibly as long as 50 to 60 years, as reported in American Indians and Alaska Natives that participated in a BCG vaccine trial [6] . In consideration for the potential protection of BCG vaccination against other infectious diseases including CoV-2 infection, Australia, which discontinued its universal BCG vaccination in the 1980s, is currently testing whether the BCG vaccination can protect healthcare workers from CoV-2 infection or reduce COVID-19-related symptoms (clinicaltrials.gov, NCT04327206). In this study, we investigated whether the BCG vaccine correlates with reported COVID-19 cases and mortality.