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As new variants of Covid emerged, vaccine developers planned to update their original vaccines, but the arrival of the fast-spreading Omicron strain in the last two months has accelerated that process.
According to the CDC, boosters should be given to Americans if at least five months have passed after finishing their Pfizer or Moderna series. However, millions of Americans who are eligible have not received these boosters.”
Health officials said the research was the first large-scale investigation of vaccine protection against Omicron in the United States.
In the papers, researchers echo previous research – including studies in Germany, South Africa, and the United Kingdom – indicating that the current Coronavirus vaccine is less effective against Omicron than earlier versions, and also that booster doses boost virus-fighting antibodies to increase the chances of avoiding symptomatic infection.
From August to this month, a study looked at hospitalizations and visits to emergency rooms and urgent care centers in 10 states.
The study found vaccine effectiveness was greatest after three doses of the Pfizer or Moderna vaccines in preventing COVID-19-associated emergency department and urgent care visits.
During the Delta wave, protection dropped from 94 percent to 82 percent.
The third study, also led by CDC scientists, appeared in the Journal of the American Medical Association.
A total of 4,600 testing sites across the country conducted COVID-19 tests from December 10 to January 1.
Compared with unvaccinated individuals, three shots of the Pfizer and Moderna vaccines were about 67 percent effective against Omicron-related symptoms.
Researchers found that two doses did not provide significant protection against Omicron when measured several months after the original series.
“If you are eligible for a booster and you haven’t gotten it, you are not up to date and you need to get your booster,” CDC Director Dr. Rochelle Walensky said during a White House briefing on Friday.