An early look at the performance of COVID-19 booster shots during the recent omicron wave in the U.S. hinted at a decline in effectiveness, though the shots still offered strong protection against severe illness.
The report, published by the Centers for Disease Control and Prevention on Friday, is considered an early and limited look at the durability of booster protection during the omicron surge that exploded in December and January but has been fading in recent weeks.
“COVID-19 vaccine boosters remain safe and continue to be highly effective against severe disease over time,” said Kristen Nordlund, a CDC spokesperson.
The researchers looked at patient visits to hospitals and urgent care centers in 10 states. They estimated how well Pfizer or Moderna booster shots prevented COVID-related visits to emergency departments and urgent care centers, and how well the vaccines prevented hospitalizations.
About 10% of people in the study were boosted. Vaccine effectiveness was higher in people who had received boosters than in people who had received only the original series of shots.