Climate & BCG: Effects on COVID-19 Death Growth Rates

M ultiple studies have suggested the spread of COVID-19 is affected by factors such as climate, BCG vaccinations, pollution and blood type. We perform a joint study of these factors using the death growth rates of 40 regions worldwide with both machine learning and Bayesian methods. We find weak, non-significant (< 3 σ ) evidence for temperature and relative humidity as factors in the spread of COVID-19 but little or no evidence for BCG vaccination prevalence or PM _2.5 pollution. The only variable detected at a statistically significant level (>3 σ ) is the rate of positive COVID-19 tests, with higher positive rates correlating with higher daily growth of deaths.