CDC study finds three in five in U.S. have had COVID-19
A study Tuesday by the Centers for Disease Control and Prevention indicates three in five Americans have had been infected with the virus that causes COVID-19, up from one in three last fall, indicating how easily the omicron variant spread through the country over the winter.
The study also found children were more likely to have been infected than older adults, with the rate among kids rising from less than one in two last fall to three in four.
“These findings show a high infection rate for the omicron variant, especially among children,” the CDC said.
But CDC officials cautioned that the findings should not be interpreted to mean that people with evidence of prior infection are protected from reinfection in the future, and continued to urge people to get vaccinated or a booster if eligible.
“Vaccination remains the safest strategy for preventing complications from SARS-CoV-2 infection, including hospitalization among children,” the CDC said. “COVID-19 vaccination following infection provides additional protection against more severe disease and hospitalization. Therefore, staying up to date with vaccination is recommended for all eligible persons, including those with prior SARSCoV-2 infection.”
The study examined the proportion of the U.S. population with “seroprevalence,” or antibodies for SARS-CoV-2, the virus that causes COVID-19, to determine how many people who have had the disease may have been missed by testing because some infections are asymptomatic, not diagnosed, or not reported.
It examined seroprevalence from September 2021 through February 2022 by age group in national survey that estimates the proportion of the population in the 50 U.S. states, the District of Columbia and Puerto Rico who were infected. Overall, it increased from 33.5% to 57.7% over the study period.
But the increase was greater among the young, from 44.2% to 75.2% among children aged 0—11 years and from 45.6% to 74.2% among adolescents and teens 12—17 years old.
By contrast, it increased from 36.5% to 63.7% among ages 18—49 years, 28.8% to 49.8% among those ages 50—64, and from 19.1% to 33.2% among those 65 and older.
Vaccination rates are higher among older people, perhaps explaining the lower numbers of prior infections among them, but the study also noted that they may be more careful than younger people about protecting themselves by avoiding crowded situations and wearing masks.
Dr. Kristie E.N. Clarke, the lead author, said the seroprevalence study can detect antibodies for the virus one to two years back, so some of the total number of people had antibodies from earlier variants of the virus, though the recent increase over the winter reflects the omicron variant which accounts for all cases today.
Clarke also said the study could not determine the level of antibodies that might indicate how protected that person would be from future infection.
“Having antibodies doesn't necessarily mean you are protected against infection,” Clarke said in a news briefing. “Vaccination provides additional protection.”
The study comes as COVID-19 cases have increased, particularly in the Northeast, though they remain well below the levels last winter driven by newer omicron subvariants BA.2 and BA.2.12.1. CDC Director Dr. Rochelle Walensky said Tuesday that cases have increased nationally nearly 23% and hospital admissions are up almost 7% in the past week, though deaths decreased 13%.
But she said it remains unclear how much antibodies from prior infection and vaccination will prevent another surge in cases and hospitalizations.
“There are some areas in country particularly in the Northeast where we're seeing higher cases and starting to see hospitalizations tick up,” Walensky said. “We're watching them carefully.”
Walensky said that so far there are no indications of an increase in intensivecare hospitalizations that suggest more serious disease from the rising cases.
“We are hopeful the positive trends will continue and we'll not see any increase in further severity of disease,” Walensky said. “This is something we need to watch carefully.”