Three US studies published yesterday provided further evidence that Covid-19 vaccines are effective against the omicron variant, at least in people who received booster doses.
These are the first large-scale U.S. studies of how well vaccines protect against omicrons, health officials said.
The conclusions are similar to earlier research, including studies in Germany, South Africa and Great Britain, which show that existing vaccines are less effective against omicrons compared to earlier versions of the coronavirus, but also that boosters can significantly improve protection, the Voice of America reported. of America).
The first study looked at hospitalizations and emergency room visits in 10 states from August to January.
Vaccine effectiveness has been found to be best after three doses of Pfizer's or Moderna's vaccine to prevent the need for emergency care or emergency room treatment.
Protection dropped from 94 percent during delta waves to 82 percent during omicron waves. The protection provided by two doses of the vaccine was lower, especially if six months had passed since the second dose.
Another study focused on coronavirus cases and deaths in 25 states from early April through Christmas.
Americans who received a booster had the greatest protection against coronavirus infection, both at a time when delta dominated, but also when omicron assumed a dominant role.
The two articles were published by the Centers for Disease Control and Prevention (CDC).
The Journal of the American Medical Association published a third study, also led by CDC researchers. It covers people who tested positive for the coronavirus from December 10 to January 1 at more than 4.600 testing centers across the US.
Three doses of the Pfizer and Moderna vaccines were about 67 percent effective against symptomatic omircon-related disease compared to the unvaccinated condition.
The two doses, however, did not provide significant protection against omicrons, the researchers found.
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