The world has surpassed over 500 million officially recorded COVID-19 cases, according to data from Johns Hopkins University. This grim milestone is almost certainly an undercount, with some researchers estimating nearly half of the world’s total population has likely been infected at least once with SARS-CoV-2 over the past two years.
With the emergence of the Omicron variant official COVID-19 cases have skyrocketed over the past few months. At the beginning of 2022 the world had formally counted less than 300 million COVID-19 cases but a month into the new year that global case count had crossed 400 million.
Now, according to the Johns Hopkins Coronavirus Resource Center, there have officially been over half a billion COVID-19 cases since the pandemic kicked off in early 2020. And this number is just the tip of the iceberg in terms of the real spread of this novel coronavirus across the world.
Since the beginning of the pandemic many researchers have stressed how official COVID-19 case counts are significantly lower than the real infection numbers. A variety of studies have tracked cases in different parts of the world and found vast numbers of undocumented cases. Even in the United States the Centers for Disease Control and Prevention (CDC) has estimated less than a quarter of infections are officially recorded.
A striking report last week from the World Health Organization analyzed more than 150 individual studies to conclude around 65 percent of all people in Africa had likely been infected with SARS-CoV-2 by the end of 2021. That is 97 times higher than the officially recorded case count on the continent.
A new study published in The Lancet, from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington in Seattle, looked to provide a comprehensive analysis of global COVID-19 cases by analyzing local data from 190 countries and territories. The researchers described the findings as “staggering”, with their estimates suggesting 3.39 billion people had been infected with COVID-19 at least once by mid-November 2021.
This equates to around 44 percent of the world’s total population. And perhaps most striking, these estimates only run up to a time point just before the Omicron variant emerged.
Up to November 14 last year the researchers calculate 400 million people globally had experienced a COVID-19 reinfection. Although the new study did not incorporate the impact of Omicron into its model, the researchers hypothesized billions more cases, including vaccine breakthrough infections and reinfections, have occurred across early 2022.
“Models suggest that more than 50 percent of the world might have been infected with Omicron already – however, a detailed analysis will have to await new seroprevalence data emerging in the coming months,” the researchers write in the new study. “Cumulative infections for COVID-19 through to March, 2022, might be nearly double what occurred through Nov 14, 2021.”
The IHME researchers also pointed out the data shows no sign of herd immunity developing in highly infected populations. Even when the model estimated local population infection levels of up to 80 percent it detected no significant decline in rates of COVID-19 infections.
The researchers hypothesize the emergence of new variants as playing a significant role in continuing high infection rates. The idea of herd immunity reducing rates of community transmission is suggested as needing, “[a] very high degree of combined natural and vaccine-derived immunity.”
Commenting on the new study Emory University epidemiologists Kayoko Shioda and Ben Lopman said the novel statistical model used by the IHME team is a technical achievement delivering robust estimates of global COVID cases. However, the duo also noted the stunning extent of global infections to date raises a host of new questions that researchers now need to investigate.
“To what extent do the population's historical infections – in terms of timing and variants – protect against infection and severe disease of new variants?” the epidemiologists asked in the Lancet commentary. “Relatedly, how do layers of vaccine-induced and virus-induced immunity combine to confer protection to the population? Perhaps most importantly at this moment in the pandemic, we need to identify the sub-populations that remain susceptible to severe disease and death.”
