Booster shots needed against omicron, CDC studies show

NEW YORK – Three studies published on Friday provided more evidence than COVID-19 vaccines resistant to the omicron variant, at least among people who received booster shots.

These are the first major U.S. studies to examine vaccine protection against omicron, health officials said.

The articles echo previous research – including studies in Germany, South Africa and the UK – indicating that 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 visits to emergency rooms and urgent care centers in 10 states from August to this month.

It found that vaccine efficacy was better after three doses of the Pfizer or Moderna vaccines in preventing emergency room visits and emergency care associated with COVID-19. Protection increased from 94% during delta wave to 82% during 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 cases and death rates in 25 states from early April through Christmas. People who were boosted had the highest protection against coronavirus infection, both during the period when delta was dominant and also when omicron took over.

Both of these articles were published online by the Centers for Disease Control and Prevention.

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

Three injections of the Pfizer and Moderna vaccines were about 67% effective against symptomatic omicron-related illness compared to 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 CDC’s Emma Accorsi, one of the study’s authors.

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The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute Department of Science Education. The AP is solely responsible for all content.