According to an antibody survey carried out by the Centers for Disease Control and Prevention (CDC) published Tuesday, 58% of the U.S. population – of more than 190 million people – had been infected with COVID-19 by February of this year.
The figure is far higher than the 80 million officially recorded cases, with most infections undiagnosed, asymptomatic or unreported.
Roughly 75% of people under 18 had been infected, according to a paper based on a nationally representative study of antibody levels. During last winter's omicron wave, there was a huge surge, particularly among children.
Each month from September 2021 to January 2022, the study examined some 75,000 blood specimens across the country and 45,000 samples in February.
The study examined only antibodies created in response to prior infection, not vaccination. National estimates were then produced using statistical methods to weight by age, sex and metropolitan status.
"Having infection-induced antibodies does not necessarily mean you are protected against future infections," said Kristie Clarke, co-lead for the national COVID-19 serology task force, on a call with reporters.
"Previous infection has been shown to provide some protection against severe disease and hospitalization – and vaccination, either before or after infection, provides additional protection," she added.
Since the duration of infection-conferred immunity is unknown, it remains vital to stay up to date with COVID-19 vaccination, she stressed.
The United States is currently offering the fourth shot to people who are 50 and above, and the third shot to people under that age. Children aged 5 and under are the only group not yet eligible for vaccination.
Nationwide cases are ticking up with infections caused by the BA.2 and BA.2.12.1 omicron subvariants. Upstate New York and the Northeast region are also experiencing an increase in hospitalizations, and the CDC recommends indoor masking in those areas, though mandates have long ceased to be in effect there.
Even with rising hospitalizations, the number of deaths continues to fall and currently stands at a little over 300 per day. The country is expected to reach the grim milestone of 1 million deaths in the coming weeks.