Estimating COVID-19 infection fatality rate in Mumbai during 2020

The aim of this piece is to provide estimates of the infection fatality rate (IFR) of COVID-19 in Mumbai during 2020, namely the fraction of SARS-CoV-2 infections which resulted in death. Estimates are presented for slums and nonslum areas, and for the city as a whole. These are based largely on the city’s official COVID-19 fatality data, seroprevalence data, and all-cause mortality data. Using recorded COVID-19 fatalities in the numerator, we obtain IFR estimates of 0.13%-0.17%. On the other hand, using excess deaths we obtain IFR estimates of 0.28%-0.40%. The estimates based on excess deaths are broadly consistent with the city’s age structure, and meta-analyses of COVID-19 age-stratified IFR. If excess deaths were largely from COVID-19, then only around half of COVID-19 deaths were officially recorded in the city. The analysis indicates that levels of excess mortality in excess deaths per 1000 population were similar in the city’s slums and nonslum areas. On the other hand the estimated ratio of excess deaths to official COVID-19 deaths in the slums was much higher than in nonslum areas, suggesting much weaker COVID-19 death reporting from the slums.