Omicron boosters probably aren't very effective against mild Covid illness, but will likely prevent hospitalizations,...

Key Points

• The CDC, in a real-world study, found the omicron Covid boosters are less than 50% effective against mild illness across almost all adult age groups when compared to people who are unvaccinated.
• But people who received the boosters were better off than those who only got the old shots, with their protection increasing 28% to 56%.
• The study did not look at hospitalization, but experts believe the shots will provide strong protection against severe outcomes.

A healthcare worker administers a dose of the Pfizer-BioNTech Covid-19 vaccine at a vaccination clinic in the Peabody Institute Library in Peabody, Massachusetts, U.S., on Wednesday, Jan. 26, 2022.

Vanessa Leroy | Bloomberg | Getty Images

The new omicron Covid boosters probably aren't very effective at preventing Covid infections and mild illness, but they will likely help keep the elderly and other vulnerable groups out of the hospital this winter, experts say.

The Centers for Disease Control and Prevention, in a real-world study published this week, found the boosters are less than 50% effective against mild illness across almost all adult age groups when compared to people who are unvaccinated.