Estimates of anti-SARS-CoV-2 antibody seroprevalence in Iran

Iran was among the first countries outside China to report a large outbreak of COVID-19, but the transmission dynamics across the country have largely remained unknown due to the scarcity of serological, epidemiological, and genomic data. One of the main barriers has been the fact that Iran's Ministry of Health and Medical Education (MoHME) stopped releasing province-level data on the number of confirmed COVID-19 cases from March 22, 2020, onward. Furthermore, provincial data on the number of confirmed COVID-19-related deaths were never released. Instead, MoHME reports the percentage change in the number of cases with respect to previous days as an indicator of the state of the epidemic in each province and colour-codes them from blue (low incidence) to yellow (medium incidence), orange (high incidence), and red (very high incidence).

Despite the significant implications of understanding the Iranian epidemic for the country and the Eastern Mediterranean region as a whole, research investigations have largely been hindered due to the lack of epidemiological data on the number of cases and deaths, age-stratified and sex-stratified data, both at the national and province level, and seroepidemiological analysis.¹ The study by Hossein Poustchi and colleagues,² sponsored by MoHME and carried out by the then Deputy Minister of Research and Technology of the Ministry of Health Reza Malekzadeh and his team, to measure SARS-CoV-2 antibody seroprevalence in the general population across 18 cities of Iran was the first systematic investigation into the geographical spread of COVID-19 across the country nearly a year after the first two cases were reported in Qom on Feb 19, 2020. Their analysis showed greatly varied levels of exposure in different cities, with some reaching very high levels (>50% in Qom and Rasht) by late April to early June.

Before the study by Poustchi and colleagues, we did a similar province-level analysis using seasonal all-cause mortality data to estimate the excess mortality in all 31 provinces of Iran from winter to summer, 2020.³ Our findings corroborate the results by Poustchi and colleagues (appendix p 1), with an overall significant correlation (R ²=0·67 and p<0·001; appendix p 2). Our results further suggest that most provinces would continue to have a two to four times increase in exposure until the end of summer (Sept 21, 2020), with Qom and Golestan reaching approximately 57% (95% CI 44–69) population-level exposure.³

In the absence of more recent serology or province-level data, our estimates provide the most recent indicator of prevalence. This comparison is of immediate epidemiological importance as it highlights areas with the largest epidemic growth, which require the most immediate interventions. The continued availability of province-level data would be of paramount public health importance in a country that is facing such a heavy toll from COVID-19.