Booster Shot Offers Significant Protection Against Omicron, CDC Studies Show

The booster shot seems to be 90 percent effective against hospitalizations with the omicron variant, the study finds

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Three shots of the Pfizer and Moderna vaccines were found to be 67 percent effective against omicron-related symptomatic disease.
Three shots of the Pfizer and Moderna vaccines were found to be 67 percent effective against omicron-related symptomatic disease.Credit: Ted S. Warren /AP

Three studies released Friday offered more evidence that COVID-19 vaccines are standing up to the omicron variant, at least among people who received booster shots.

They are the first large U.S. studies led by the Centers for Disease Control, to look at vaccine protection against omicron, health officials said.

The papers echo previous research — including studies in Germany, South Africa and the U.K. — indicating available vaccines are less effective against omicron than earlier versions of the coronavirus, but also that boosters significantly improve protection.

The first study looked at hospitalizations and emergency room and urgent care center visits in 10 states, from August to this month.

The booster shot seems to be 90 percent effective against hospitalization with the omicron variant, according to the CDC study. 

The study found vaccine efficacy was highest after three doses of the Pfizer or Moderna vaccines in preventing COVID-associated emergency department and urgent care visits. Protection dropped from 94 percent during the delta wave to 82 percent during the omicron wave. Protection from just two doses was lower, especially if six months had passed since the second dose.

The second study focused on COVID-19 case and death rates in 25 states from the beginning of April through Christmas. People who were boosted had the highest protection against coronavirus infection, both during the time delta was dominant and also when omicron was taking over.

The Journal of the American Medical Association published the third study, also led by CDC researchers. It looked at people who tested positive for COVID-19 from December 10 to January 1 at more than 4,600 testing sites across the U.S.

Three shots of the Pfizer and Moderna vaccines were about 67 percent effective against omicron-related symptomatic disease compared with unvaccinated people. Two doses, however, offered no significant protection against omicron, the researchers found.

“It really shows the importance of getting a booster dose,” said the Emma Accorsi, one of the study’s authors.

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