Lifestyle Health Nearly 60% of Americans — and 3 in 4 Kids — Have Now Had COVID, CDC Says Health officials warned, though, that prior COVID-19 illness does not mean that people are protected from getting it again, and urged Americans to stay up-to-date on vaccinations By Julie Mazziotta Julie Mazziotta Twitter Julie Mazziotta is the Sports Editor at PEOPLE, covering everything from the NFL to tennis to Simone Biles and Tom Brady. She was previously an Associate Editor for the Health vertical for six years, and prior to joining PEOPLE worked at Health Magazine. When not covering professional athletes, Julie spends her time as a (very) amateur athlete, training for marathons, long bike trips and hikes. People Editorial Guidelines Published on April 26, 2022 04:38 PM Share Tweet Pin Email Child getting tested for COVID. Photo: Getty Images Back in December, before the omicron variant swept through the country, slightly over a third of Americans had been infected with COVID-19. But just two months later, after the highly contagious variant led to thousands of new cases, most Americans had been infected at least once, a new study from the Centers for Disease Control found. Using data from blood tests taken around the country, the CDC determined that 33.5% of Americans had COVID-19 antibodies that developed from infection, and not vaccination, in Dec. 2021. By Feb. 2022, that percentage had jumped significantly, up to 58%. The biggest increase was in kids under 18 — by February, 75%, or 3 in 4 kids, had COVID-19 antibodies in their system. "By February 2022, evidence of previous Covid-19 infections substantially increased among every age group," Dr. Kristie Clarke, a CDC researcher who led the study, said at a press briefing. The jump in the prevalence of antibodies made sense given the omicron surge, Clarke said, but was still a surprise. "I definitely expected to see an increase continue," she said. "I didn't expect it to increase quite this much but we look at the data and that's what the evidence is showing us." The CDC's research gives a more accurate look at the number of COVID-19 cases nationwide than the reported cases, which do not account for any tests that are taken at home and not reported to local health departments, or cases where people do not take a test to confirm that they're positive. "We know that reported cases are just the tip of the iceberg," Clarke said. RELATED VIDEO: 29-Year-Old Runner Shares Her Struggle with Long COVID: 'I'm a Different Person' She also added that this is the first time that the prevalence of antibodies has been over 50% in the U.S. And while the majority of Americans have now had COVID-19 at least once, both Clarke and CDC Director Dr. Rochelle Walensky cautioned that a prior infection "does not mean that you're protected" from getting the virus again, especially if another variant rises up to surpass omicron. They said that vaccination is still the best protection against COVID-19, and that the sharp rise in cases among kids is likely because they have the lowest vaccination rates — though children age 5 to 11 have been eligible for vaccination since the beginning of November, just 28.4% are fully vaccinated as of April 26, according to the CDC. "We continue to recommend that everyone be up to date on their vaccinations, get your primary series and booster, when eligible," Walensky said.