Estimate: Less than half the world has had COVID-19

From March 2020 to the emergence of the Omicron variant in late 2021, about 3.8 billion COVID-19 infections and reinfections occurred, with nearly 44% of the world's population infected at least once but with wide regional variations, estimates a statistical analysis of 190 countries and territories published late last week in The Lancet.Led by Institute for Health Metrics and Evaluation researchers, the COVID-19 Cumulative Infection Collaborators created and refined statistical models of global and location-specific daily and cumulative COVID-19 infections using data from Johns Hopkins University, national databases, and seroprevalence surveys, adjusting for lags in reporting, undercounting of deaths, waning antibody sensitivity, vaccinations, and reinfection by SARS-CoV-2 variants.No indication of herd immunityWorldwide, new daily COVID-19 infections ranged from 3 million to 17 million from April 2020 to October 2021, peaking in mid-April 2021, largely due to case surges in India.

Up to Nov 14, 2021, an estimated 3.8 billion total COVID-19 infections and reinfections occurred, with about 3.4 billion people (43.9% of the world's population) infected at least once.Of all infections and reinfections, 1.3 billion occurred in South Asia, the highest count of all regions, but the highest infection rate (79.3%) was in sub-Saharan Africa.

High-income countries had the fewest cases, at 239 million, while Southeast Asia, East Asia, and Oceania had the lowest infection rate (13.0%).

The rate in the United States and Canada was 30.9%, while the rate in Western Europe was 48.9%The total percentage of the population infected at least once ranged from 20% in 39 countries to more than 70% in 40 countries.