Blood taken from a registered nurse for a coronavirus antibody test on June 16, 2020 in Washington, DC.
Win McNamee | Getty Images
Three out of five people in the United States already have antibodies from a previous Covid-19 infection, and the proportion is even higher among children, showing how widespread the virus is during the winter omicron, according to data from the Centers for Disease Control and Prevention. diseases. .
The proportion of people with natural Covid antibodies increased significantly from about 34% of the population in December to about 58% in February during an unprecedented wave of infections caused by the highly contagious version of omicron. The CDC analysis does not take into account people who have antibodies to vaccination.
The CDC released the data in its weekly report on morbidity and mortality on Tuesday.
The increase in the spread of antibodies is most pronounced among children, which shows a high rate of infection among children during the winter omicron wave. About 75% of children and teens already have antibodies from past Covid infections, up from about 45% in December.
The high infection rate among children is probably due to lower levels of vaccination than adults. Only 28% of children aged 5 to 11 and 59% of teenagers aged 12 to 17 were fully vaccinated by April. Children under the age of 5 still do not qualify for vaccination.
About 33% of people aged 65 and over, the group with the highest vaccination rates, had antibodies to the infection. Approximately 64% of adults aged 18 to 49 years and 50% of people aged 50 to 64 had antibodies.
The CDC analyzes about 74,000 blood samples each month from September to January from a national commercial laboratory network. The sample size dropped to about 46,000 blood samples in February. The CDC tests samples for a specific type of antibody that is produced in response to Covid infection, not vaccination.
CDC officials told reporters during an interview Tuesday that the study did not measure whether people with previous infections had high enough antibody levels to prevent re-infection and severe illness. However, CDC Director Dr Rochelle Valenski said health officials believe there is much protection in communities across the country against vaccination, reinforcements and infection combined, while warning that vaccination is the surest protection strategy. against the virus.
“Those who have detectable antibodies from a previous infection, we continue to encourage them to be vaccinated,” Valenski told reporters during a conversation. “We don’t know when this infection was. We don’t know if this protection has diminished. We don’t know as much about this level of protection as we do about the protection we get from both vaccines and boosters.”
Researchers at Cornell University in Qatar have found that natural infection provides about 73% protection against hospitalization if a person is re-infected with BA.2. However, three doses of Pfizer vaccine provide much higher protection against hospitalization in 98%. The study, published in March, was not subject to peer review.
About 66% of the US population is fully vaccinated and 77% have received at least one dose, according to the CDC.
Infections and hospitalizations fell by more than 90% from the peak of the omicron wave in January, when infections in the United States rose to an average of more than 800,000 per day. The new cases are increasing again due to sub-option BA.2. Another sub-option, BA.2.12.1, is now prevalent in the United States, accounting for about 29% of new infections, according to the CDC. Valenski said the public health agency believes BA.2.12.1 is spreading about 25% faster than BA.2. However, she said the CDC did not expect to see a more severe disease than BA.2.12.1, although studies are ongoing.
More than 98% of the US population lives in areas where it is not necessary to wear masks indoors under the guidance of the CDC due to the low levels of the Covid community, which takes into account both infections and hospitalizations. A U.S. district judge last week revoked the CDC’s mandate for public transport masks, although the Department of Justice has filed a complaint. Valenski said the CDC continues to recommend people wear masks on public transport.
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