But officials caution that people should not presume they have protection against the virus going forward.
Before omicron, one-third of Americans had been infected with the coronavirus, but by the end of February, that rate had climbed to nearly 60 percent — including about 75 percent of kids and 60 percent of people age 18 to 49, according to federal health data released Tuesday.
The data from blood tests offers the first evidence that over half the U.S. population, or 189 million people have been infected at least once since the pandemic began — double the number reflected in official case counts. Officials cautioned, however, that the data, in a report from the Centers for Disease Control and Prevention, does not indicate people have protection against the virus going forward, especially against increasingly transmissible variants.
“We continue to recommend that everyone be up to date on their vaccinations, get your primary series and booster, when eligible,” CDC Director Rochelle Walensky said during a media briefing.
Kristie Clarke, the CDC official who authored the report, said by February, “evidence of previous COVID-19 infections substantially increased among every age group, likely reflecting the increase in cases we noted as omicron surged in this country.”
Clarke said the greatest increases took place in those with the lowest levels of vaccination, noting that older adults were more likely to be fully vaccinated.
The largest increases were in children and teenagers through age 17 — about 75 percent of them had been infected by February, based on blood samples that look at antibodies developed in response to a coronavirus infection but not in response to vaccination. That’s about 58 million children.
The blood test data suggests 189 million Americans had covid-19 by end of February, well over double the 80 million cases shown by The Washington Post case tracker, which is based on state data of confirmed infections. Clarke said that’s because the blood tests captures asymptomatic cases and others that were never confirmed on coronavirus tests.
With the omicron surge, officials had expected there would be more infections. “But I didn’t expect the increase to be quite this much,” Clarke added.
Separately, CDC is about to publish another study that estimates three infections for every reported case, she said.