Differential COVID-19-attributable mortality and BCG vaccine use in countries

Anita Shet; Debashree Ray; Neelika Malavige; Mathuram Santosham; Naor Bar-Zeev

To evaluate the effect of BCG vaccine on mortality attributable to COVID-19, we built a simple log-linear regression model using crude COVID-19-attributable mortality data per 1 million population for each country as outcome, BCG vaccine inclusion in the national immunization schedule as exposure, and adjusted for the effects of the following variables on mortality: country-specific GDP per capita, the percentage of population 65 years and above, and the relative position of each country on the epidemic timeline (days since 100 th case reported as of 29 March 2020). The Shapiro-Wilk normality test confirmed that the log-transformed COVID-19-specific mortality was normally distributed. As China, a BCG-using country with a large population and a relatively concentrated death count in a single province can conceivably demonstrate an artifically lowered mortality and skew these results towards BCG use, we did a sensitivity analysis by running our model with the same covariate adjustments but without China. All data were analysed using the R environment for statistical computing (R Core Team 2018) 15 .