Blood samples collected and tested from the beginning of the pandemic through the end of January 2022 indicate that more than 140 million Americans have had COVID-19 so far, equivalent to roughly 43.3% of the population, according to the Centers for Disease Control and Prevention.
The “nationwide antibody seroprevalence” survey uses data from over 71,000 samples taken across the country throughout the pandemic to estimate the spread of COVID-19 over time.
It doesn’t include people in the U.S. who have been vaccinated, a figure the CDC says stands at 64.9% ― though that depends on how it’s defined.
It also excludes Arizona, North Dakota, Nevada and Utah, none of which submitted enough samples to be statistically significant.
Notably, the survey looks only at the presence of detectable antibodies, not the amount of antibodies present. As such, it’s not an accurate count of the percent of the U.S. population with sufficient antibodies to prevent reinfection.
The prevalence varies significantly by age: While an estimated 57.8% of children under the age of 18 have likely had COVID-19, the figure for people age 65 and over is just 23%. For people between the ages of 50 and 64, the figure is 37.1%; for age 18 to 49, it’s 48%.
The survey also comes with more than a few caveats. It’s impossible to sort out people who have been infected more than once, for instance. It’s also difficult to account for people who have been infected but were asymptomatic and/or went untested.
The survey also relies on samples through the end of January, meaning a significant number of cases caused by the highly transmissible omicron variant have gone uncounted.
Among other large, high-income countries like Australia, Japan and Canada, the United States ranks last in vaccinations. It makes sense, then, that the U.S. far outpaced those countries in deaths during the omicron wave.
This article originally appeared on HuffPost and has been updated.