By Alexander Tin

More than 90% of children in the U.S. have survived at least one infection by SARS-CoV-2, the virus that causes COVID-19, based on data collected from commercial laboratories around the country through October.

The Centers for Disease Control and Prevention's new "seroprevalence" estimates, published Thursday, look at whether people have detectable antibodies in their blood from at least one prior COVID-19 case. They could still be at risk of reinfection from the new variants circulating this winter.

"The estimates do not necessarily show how many people have enough antibodies to protect them against reinfection, severe outcomes, and/or COVID-19-related complications," the CDC says.

Since 2020, the federal government has been producing these estimates based on sampling blood that commercial laboratories collect for reasons other than COVID-19, like routine check-ups.

Measurements of prior infection among children have far outpaced adults over the course of the pandemic, in the CDC's figures.

The CDC estimated earlier this year that still less than half of adults had infection-induced antibodies through March, the latest data for which the CDC has estimates for this age group. By contrast, the CDC had already tallied 75% of children with antibodies through February.

A more recent estimate for adults through June is planned soon, a CDC spokesperson said, with additional updates planned "approximately every 3 months after that."

Among the states with reported data, Hawaii is the only state under 80% seroprevalence in children. Many states are estimated at or above 90%.

Nationwide, all of the age groups broken out by the agency show upwards of 8 in 10 children having had COVID-19 at least once. Kids 5 to 11 years old have the highest seroprevalence rate, at 92.1%.

The new figures come as the Biden administration has struggled to persuade families to get their children vaccinated against COVID-19, despite evidence that the shots are safe for kids and can reduce the odds of children facing severe illness or spreading it to others.

Less than half of children under 12 years old and under two-thirds of teens have finished their primary series COVID-19 vaccinations, according to CDC figures. A small fraction have received their updated COVID booster.

Data published this week from the CDC's National Immunization Survey suggest vaccine hesitancy is continuing to grow among families.

Among children under 5 years old, where vaccination coverage is lowest, the agency now estimates that nearly half of parents "probably or definitely" will not get their kids vaccinated.

Uptake of the COVID shots is far lower than the annual flu shot; the CDC estimates 42.5% of children had gotten a flu shot through the end of last month. That is on par with previous years, which typically reach around 60% vaccination by the end of the season.

The agency also published new data on Thursday warning that children could be at risk of rare but serious co-infections of COVID-19 and influenza, as infections of the two viruses have increased in some parts of the country.

Last season, when the U.S. saw a relatively small wave of flu hospitalizations, the agency tallied 6% of hospitalized pediatric flu patients co-infected with SARS-CoV-2. About 16% of flu deaths in kids last season had a co-infection.

The findings underscore that "influenza and SARS-CoV-2 coinfections occur in pediatric patients and that coinfection can potentially cause more severe illness," the study's authors wrote.

"The public should adopt prevention strategies, including influenza and COVID-19 vaccination, and consider mask use during high respiratory virus circulation," they said.