Seroprevalence studies differ from typical national statistics of PCR-based “confirmed cases” of the virus inasmuch as they do not simply detect active traces of SARS-CoV-2, but rather the presence of
COVID antibodies, thus counting those individuals infected with the pathogen at some point but who may or may not have active viral material in their body at the time of testing.
Aggregating the six systematic evaluations, Ioannidis found that all “seroprevalence data converge that SARS-CoV-2 infection has been very widely spread globally,” resulting in a global IFR of approximately 0.15% with 1.5-2.0 billion infections as of February 2021.
The IFR calculated in Ioannidis’ latest research is a revision of his previous findings, which concluded that COVID-19 had a 0.23% IFR, making COVID-19 around 1.5 times less deadly than previously thought. In concrete terms, the revised IFR puts COVID-19 a bit higher in fatality rate than Influenza, which generally sits at 0.1% IFR.
According to Ioannidis, the majority of the evaluations used in his report reached “congruent estimates of global pandemic spread.” These estimates show around 600 million people were already infected with the virus before the end of November 2020, not taking account of infections in the bulk of Africa and Asia. Adjusted to include national statistics of viral infection from these regions, Ioannidis concluded that around 1 billion people worldwide had come into contact with SARS-CoV-2 before the end of November.
“By extrapolation, one may cautiously estimate [approximately] 1.5 – 2.0 billion infections as of 21 February 2021 (compared with 112 million documented cases),” Ioannidis said. “This corresponds to global IFR [of approximately] 0.15%,” a figure, he noted, that is “open to adjustment for any over- and under-counting of COVID-19 deaths.”
“Differences are driven by population age structure, nursing home
populations, effective sheltering of vulnerable people, medical care, use of effective or detrimental treatments,” he explained. “IFR will depend on settings and populations involved. For example, even ‘common cold’ coronaviruses have IFR [of approximately] 10% in nursing home outbreaks,” almost 67 times greater than the average global IFR of COVID-19, per Ioannidis’ study.