Booster shots of the Pfizer and Moderna COVID-19 vaccines appear to be highly effective at preventing hospitalizations due to the Omicron variant, according to three new CDC studies published on Friday.
The extra doses were 90% effective at keeping people out of the hospital after infection and 82% effective at preventing emergency department and urgent care visits.
“These reports add more evidence to the importance of being up to date with COVID vaccinations,” Rochelle Walensky, MD, director of the CDC, said Friday during a news briefing by the White House COVID-19 Response Team.
Data from Israel and other countries have suggested that booster shots can prevent severe illness and hospitalization, but it hasn’t been clear until now whether extra doses would have the same effect in the U.S. In the three CDC studies, researchers reviewed millions of cases and tens of thousands of hospitalizations and deaths during the Delta and Omicron waves.
In one study, researchers analyzed hospitalizations and visits to emergency departments and urgent care clinics in 10 states between the end of August 2021 and beginning of January 2022. Vaccine effectiveness against hospitalization with Omicron fell to 57% for those who had received their second dose more than 6 months earlier. A booster shot restored protection to 90%.
In a second study, researchers analyzed nearly 10 million COVID-19 cases and more than 117,000 deaths reported at 25 state and local health departments between April and December 2021. Cases and deaths were lower among people who had received a booster dose, as compared with those who were fully vaccinated but not boosted. Cases and deaths were even lower among boosted Americans than among those who were unvaccinated.
In a third study, which was published in JAMA, the journalof the American Medical Association, researchers looked at data from more than 70,000 people who got tested for COVID-19. A third dose provided more protection against infections with symptoms than two doses or no doses. Full vaccination and boosters protected less against the Omicron variant than against the Delta variant.
The CDC also released data on Thursday that showed unvaccinated adults ages 65 and older who are infected with COVID-19 are 49 times more likely to be hospitalized than those who are vaccinated and have received booster shots. Among ages 50 and older, unvaccinated adults are 45 times more likely to be hospitalized than those who are vaccinated and boosted.
“There are still millions of people who are eligible for a booster dose and have not yet received one,” Walensky said Friday. “As we continue to face the Omicron variant, representing over 99% of infections in the United States today, I urge all who are eligible to get their booster shot to get it as soon as possible.”
White House: “Press Briefing by White House COVID-19 Response Team and Public Health Officials,” Jan. 21, 2022.