Does TB Vaccination Reduce COVID-19 Infection?: No Evidence from a Regression Discontinuity Analysis

Masao Fukui; Kohei Kawaguchi; Hiroaki Matsuura

These previous findings are based on the cross-country association between health outcomes of COVID-19 and the national BCG vaccination policies, thus do not exclude the possibility of spurious correlation. For example, a country with higher BCG vaccination coverage is more likely to be poor as infectious diseases (such as TB) are still leading causes of death. Such country is less likely to be connected to the major economic regions such as China, Europe, and the United States due to their trade openness and geographic location. There is an imminent need to re-examine this newly emerging hypothesis for two reasons. If there is no possibility, the society should spend more effort searching for more plausible solutions to combat COVID-19. Moreover, if people demand BCG vaccination for COVID-19, this creates a shortage for BCG vaccination for children who actually need it. In fact, Japan BCG Laboratory, the only producer of BCG vaccine in Japan, shipped three times more vaccine in March 2020 than the average in the past. 1 The Japan Society for Vaccinology recently warned that BCG vaccination was for preventing TB, not for other purposes in their official statement. 2 We believe that clinical trials can provide us with a secure basis for the effectiveness of BCG vaccination against COVID-19, but it is worth reexamining this purported hypothesis using a more credible identification strategy before spending more time and resources to test it. In this paper, we test this hypothesis with a best available identification strategy based on observational data: a regression discontinuity and difference-in-difference analysis.