CDC study shows 75% of children had COVID infection

OAKLAND - More than half of the United States population has had a COVID-19 infection according to a new study released by the Centers for Disease Control and Prevention Tuesday. The rate was even higher among children, the study said.

The study analyzed blood samples from more than 200,000 Americans and searched for a specific antibody that is only created from a COVID-19 infection, not a vaccine.

Researchers say the data also found that three out of four children ages 17 and younger in the United States have had a COVID-19 infection, with a big jump in cases during the winter months as the milder, but highly infectious Omicron variant was spreading.

For Americans of all ages, about 34% had signs of prior infection in December. Just two months later, 58% did. The percentage of those 17 and under with antibodies rose from about 45% in December to about 75% in February.

"So an awful lot of people got infected during December in January and in parts of February," said Dr. John Swartzberg, an infectious disease specialist and Clinical Professor Emeritus at the UC Berkeley School of Public Health, "This virus just burns through a population."

Some parents say they're not surprised.

"Even before COVID, daycare or schools, they got sick often, so it does not sound surprising that they're catching it from each other," said Daniel Burton, a Castro Valley parent.

One Alameda family says both of their kids have had the COVID vaccine and haven't been sick, but at school, there have been a consistent string of cases.

"In the last four months, have been pretty much 1-2 children who've caught COVID," said Matt Losinger, an Alameda parent, "This month was four."

The CDC study results come as Pfizer asked the FDA Tuesday to authorize a COVID vaccine booster dose for healthy children ages 5 to 11. Pfizer is recommending those children get a booster dose six months after their last shot.

Swartzberg says Pfizer's data needs to be reviewed, but if it's deemed safe a booster could be an important tool to help protect children from COVID-19.

"It causes more sickness, serious sickness, death than influenza does in children," said Swartzberg.

Swartzberg says scientists still don't know COVID's long-term effects, and previous COVID infection does not protect against future illness.

"We've learned that unlike measles, if you've gotten measles once, you're never going to get it again. But if you get COVID once, our immunity to COVID whether it's an infection or whether it's the vaccine, it does wane," said Swartzberg.

The case numbers are believed to be an undercount, but officials do think recent increases reflect a true rise in 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 soon that estimates that in recent months there were three infections for every reported case.

Another recent trend: U.S. health officials say they have seen two weeks of increases in COVID-19 hospitalizations, though the numbers remain relatively low. Hospital admissions number about 1,600 per day, a 9% increase in the prior week, the CDC reported.

Available evidence nevertheless offers 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 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 hospitalization, 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 Americans to get vaccines and boosters, which offer additional protection against COVID-19 for all, including those who were previously infected.

Jana Katsuyama is a reporter for KTVU.  Email Jana at jana.katsuyama@fox.com and follow her on Twitter @JanaKTVU or Facebook @NewsJana or ktvu.com.