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An estimate of the COVID-19 infection fatality rate in Brazil based on a seroprevalence survey

Our take —

This ecological study used patient data from three large Brazilian national datasets to calculate a national infection fatality rate (IFR) for Covid-19 of 1.05%, representing 133 cities and 36% of the population. The increase in IFR from May to June 2020 likely represents the increasing saturation of the healthcare system. Though there are a few limitations, the study represents a robust estimate of IFR, adding to the picture previously provided only by modeling.

Study design

Ecological

Study population and setting

This study calculated a population level estimate for COVID-19 infection fatality rate (IFR), utilizing three datasets from Brazil: 1) EPICOVID19-BR, a seroprevalence survey which tested 89,397 individuals (as of July 1, 2020) in three stages, over five weeks, across 28 states in Brazil; 2) SIVEP-Gripe dataset, a prospectively collected respiratory infection registry of Severe Acute Respiratory Syndrome (SARS) cases across both public and private hospitals maintained by the Ministry of Health, which includes 97,924 patients (as of June 16, 2020) with SARS-CoV-2 positive RT-PCR tests; and 3) Painel Coronavírus dataset recording 42,309 Covid-19 fatalities as of July 17, 2020, in 133 Brazilian cities, the Brazilian reference to keep track of the pandemic at the federal level and provides the deaths by COVID-19 with their geographic location.

Summary of Main Findings

The study calculated a country-wide average IFR of 1.05% (95% CI: 0.96–1.17%), and found evidence for the IFR increasing starting in June 2020. This estimate is in agreement with some, but not all, of the previous world estimates. They found a jump in COVID-19 prevalence from late May to early June, and a stabilization in late June. They calculated a mean of 10.3 days from development of antibodies to death, for the whole of Brazil.

Study Strengths

The study is based on three large Brazilian national datasets, with 42,000 individuals in the smallest, and 98,000 individuals in the largest. The sample included 133 cities around the country, accounting for over a third of the population. Their IFR calculation uses seroprevalence estimates rather than modeling, yielding a more accurate representation. They corrected for false positive and false negative test rates to more accurately estimate prevalence. They properly accounted for the estimated time delay between the development of symptoms and subsequent fatality. Their estimate is also quite precise, with a small statistical error.

Limitations

The EPICOVID19-BR study did not hit its target of 250 individuals per city per round, potentially underrepresenting areas with less access to services or trust of healthcare, which could lead to underestimating the IFR. Conversely, the study assumes that SARS-CoV-2 antibodies remain present in patients, which could lead to an underestimation of the percentage of Brazilians that have been infected, which would thus overestimate the IFR. Also, it may be that not all COVID-19 deaths are registered in the Painel Coronavírus dataset. This would more likely be the case for out-of-hospital fatalities and in the poorest areas with less healthcare infrastructure, but as the study focusses on 133 key cities, this bias is likely limited. The population of those cities included 35.5% of the Brazilian population, which is sizable, however the results only apply to those cities, and the IFR may be different in smaller cities and rural or poorer areas which may have less robust healthcare available.

Value added

This is the first IFR estimate for Brazil based on patient data rather than modeling.

This review was posted on: 16 October 2020