BACKGROUND:
Estimates of
community spread and
infection
fatality rate (IFR) of COVID-19 have varied across studies. Efforts to
synthesize the evidence reach seemingly discrepant conclusions.
METHODS:
Systematic evaluations of
seroprevalence
studies that had no restrictions based on country and which estimated
either total number of people infected and/or aggregate IFRs were
identified.
Information was extracted and compared on eligibility criteria, searches, amount of evidence included, corrections/
adjustments of
seroprevalence and
death counts, quantitative syntheses and handling of heterogeneity, main estimates and global representativeness.
RESULTS:
Six systematic evaluations were eligible. Each combined data from 10 to
338 studies (9-50 countries), because of different eligibility
criteria. Two evaluations had some overt flaws in data, violations of
stated eligibility criteria and biased eligibility criteria (eg
excluding studies with few deaths) that consistently inflated IFR
estimates. Perusal of quantitative synthesis
methods also exhibited several challenges and
biases. Global representativeness was low with 78%-100% of the evidence coming from
Europe or the
Americas;
the two most problematic evaluations considered only one study from
other continents. Allowing for these caveats, four evaluations largely
agreed in their main final estimates for global spread of the
pandemic and the other two evaluations would also agree after correcting overt flaws and
biases.
CONCLUSIONS:
All systematic evaluations of
seroprevalence
data converge that SARS-CoV-2 infection is widely spread globally.
Acknowledging residual uncertainties, the available evidence suggests
average global IFR of ~0.15% and ~1.5-2.0 billion
infections by February 2021 with substantial differences in IFR and in
infection spread across continents, countries and locations.
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