Detailed reconstruction of the Iranian COVID-19 epidemic reveals high attack rates of SARS-CoV-2 in several provinces

Since the first cases of COVID-19 were reported in Qom, Iran, almost 19 months ago, the transmission dynamics across the country and the health burden of COVID-19 has remained largely unknown due to the scarcity of epidemiological analyses and lack of provincial data on the number of COVID-19 cases and deaths. For the first time, we reconstruct the epidemic trajectory across the country and assess the level of under-reporting in infections and deaths using province-level age-stratified weekly all-cause mortality data. Our estimates suggest that as of 2021-09-17, only 48% (95% confidence interval 43-55%) of COVID-19 deaths in Iran have been reported. We find that in the most affected provinces such as Qazvin, Qom, and East Azerbaijan approximately 0.4% of the population have died of COVID-19 so far. We also find significant heterogeneity in the estimated attack rates across the country with 11 provinces reaching close to or higher than 100% attack rates. Despite a relatively young age structure in Iran, our analysis reveals that the infection fatality rate gradually increased over time in several provinces and reached levels that are comparable some of the high-income countries with a larger percentage of older adults, suggesting that limited access to medical services, coupled with undercounting of COVID-19-related deaths, can have a significant impact on COVID-19 fatalities. These results also show that despite several waves of infection and high attack rates in many provinces with largely unmitigated epidemics, herd immunity through natural infection has not been achieved.