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

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

Novel SARS-CoV2 continues to wreak global havoc. Mortality is of greatest concern directly influencing national response and policy. Early reports from Hubei province in China reported a case fatality rate (CFR) of 15% 1 , which with widening surveillance, rapidly decreased to below 3% 2,3 . As new epidemics began in other countries, early testing strategies focused only on severe cases or contacts of known cases and those with known international travel, leading to positively biased CFR estimates. A high CFR of 7.2% reported in Italy was attributed to a greater proportion of the elderly in the population and a stringent testing strategy restricted to severe disease cases 4 . With concurrent outbreaks occurring globally, marked discrepancies in CFR became increasingly apparent. In east Asian countries (Vietnam, Thailand, and Philippines), early rises in case incidence have not been followed by similarly sharp CFR increases. CFR estimation is sensitive to testing strategies, initiation of distancing measures, access to healthcare and population age structure. We surmised that since susceptibility to COVID-19 infection extends to the entire population, crude national COVID-19-specific mortality within the country-specific population would be an informative outcome indicator to study differences in mortality patterns amongst countries, in addition to a priori defined potential exposure variables including BCG vaccine use in national immunization schedules.