New study estimates that 3 in 4 kids in the US have had coronavirus, and more than half of all Americans
- Researchers at the Centres for Disease Control examined blood samples for antibodies from previous infections and found rates have surged since Omicron
- The number of hospitalisations due to Covid has risen, but numbers still remain relatively low
People enter and exit a subway car in New York City. Many Americans have stopped wearing masks since mandates have ended. Photo: EPA-EFEThree out of every four US children have had coronavirus and more than half of all Americans show signs of previous infection, researchers at the Centres for Disease Control and Prevention (CDC) estimated in a report on Tuesday.
The researchers examined blood samples from more than 200,000 Americans and looked for virus-fighting antibodies made from infections, not vaccines. They found that signs of past infection rose dramatically between December and February, when the more contagious Omicron variant surged through the US.
For Americans of all ages, about 34 per cent had signs of prior infection in December. Just two months later, 58 per cent did.
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“I did expect it to increase. I did not expect it to increase quite this much,” said Dr Kristie Clarke, co-leader of a CDC team that tracks the extent of coronavirus infections.
The news came as Pfizer sought permission to offer a booster shot to kids aged 5 to 11, just like people 12 and older can get.
In the CDC report, the most striking increase was in children. The percentage of those 17 and under with antibodies rose from about 45 per cent in December to about 75 per cent in February.
The older people were, the less evidence there was of past infections. That may be because older adults have higher vaccination rates and are more likely to take other Covid-19 precautions, such as wearing masks and avoiding crowds, Clarke said.
Reported Covid-19 cases surged in December and January, then fell almost as dramatically as they had risen. But daily case counts have been rising again in recent weeks.
Officials say that while they believe the case numbers are an undercount, it does reflect a true rise in the number of infections. Many Covid-19 infections are mild enough that patients do not seek care or confirmatory lab tests. CDC officials say they plan to release a study that estimates that in recent months, there were three infections for every reported case.
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Another recent trend: US health officials say they have seen two weeks of increases in Covid-19 hospitalisations, though the numbers remain relatively low. Hospital admissions number about 1,600 per day, a 9 per cent increase from the prior week, the CDC reported.
The available evidence offers a reason to be hopeful about how the pandemic is going, officials suggested.
“We are not anticipating more severe disease from some of these subvariants, but we are actively studying them,” CDC Director Dr. Rochelle Walensky said on Tuesday.
The tests that showed how many people had previous infections can detect antibodies for one to two years after infection, and possibly longer. Studies have shown previous infection can protect some people against severe disease and hospitalisation, but CDC officials stressed that the previously infected should still get Covid-19 vaccines.
The study looked for any detectable level of antibodies; it did not distinguish how many people had antibody levels that might be protective. Scientists are still trying to understand what role these kinds of antibodies play in protection from future virus exposures.
Officials continue to urge everyone to get vaccines and boosters, which offer additional protection against Covid-19 for all, including those who were previously infected.