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

Masao Fukui; Kohei Kawaguchi; Hiroaki Matsuura

The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10.1101/2020.04.13.20064287 doi: medRxiv preprint cination policy (34 years old). In (e) Singapore, there is no significant decrease after coverage (77 years old), and the start of the vaccination policy (62 years old). In summary, results from regression discontinuity analysis do not support either the positive BCG effects, or the stronger BCG effects with the Japan and Russia/Bulgaria strains. Some argue that the effect of BCG lasts only for 20 to 30 years and hence would not be detected at old cohorts. However, the apparent no effect at the age of termination of the universal vaccination policy in the Czech Republic in 2010 would address this issue. Figure 2 displays the results of the difference-in-difference analysis. The Figure's left panel shows the scatter plot of residualized log cases per thousand and the residualized BCG coverage ratio after controlling for country and age-group dummies from Model (1). If the BCG reduces COVID-19 infection, we should expect a negative slope: however, here the slope is positive, indicating that our results do not support the purported BCG effects on COVID-19 infection. The right panel of Figure 2 shows the scatter plot of residualized log cases per thousand and the residualized BCG coverage with the Japan or the Russia/Bulgaria strains. The highlighted circles represent Japan, Thailand, Colombia, and Latvia where the Japan or Russia/Bulgaria strains were once used. Again, we do not observe a negative slope: therefore, our results do not support the hypothesis that the Japan and the Russia/Bulgaria strains that are close to the original Tuberculosis are especially effective. This difference-in-difference analysis includes cohorts for which the universal BCG vaccination coverage terminated during 1990s and 2000s. Thus, the result also addresses the problem that potential BCG effects last only for 20 to 30 years. Note that when we remove the country fixed effects, the sign of the coefficient becomes significantly negative, consistent with the previous cross-country analysis of Miller et al. (2020) . This underscores the importance of controlling for unobserved country-specific characteristics.