Countries with mandatory policies to vaccinate against tuberculosis register fewer coronavirus deaths than countries that don’t have those policies, a new study has found.

The preliminary study posted on medRxiv, a site for unpublished medical research, finds a correlation between countries that require citizens to get the bacillus Calmette-Guerin (BCG) vaccine and those showing fewer number of confirmed cases and deaths from COVID-19. Though only a correlation, clinicians in at least six countries are running trials that involve giving front-line health workers and elderly people the BCG vaccine to see whether it can indeed provide some level of protection against the new coronavirus.

Gonzalo Otazu, assistant professor at the New York Institute of Technology and lead author of the study, started working on the analysis after noticing the low number of cases in Japan. The country had reported some of the earliest confirmed cases of coronavirus outside of China and it hadn’t instituted lockdown measures like so many other countries have done.