COVID-19 Resource Center

COVID-19 Resource Center


Press Briefing

Disclosures: Fauci and Walensky report no relevant financial disclosures. Please see the studies for all authors’ relevant financial disclosures.
January 21, 2022
2 min read

Officials urge Americans to get boosted as reports show benefit against omicron


Press Briefing

Disclosures: Fauci and Walensky report no relevant financial disclosures. Please see the studies for all authors’ relevant financial disclosures.
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Booster doses of COVID-19 vaccine provide the best protection against the omicron variant, according to data from three new studies published Friday, including two in MMWR.

“As the numbers indicate, we are seeing the number of cases caused by the omicron variant begin to decline,” CDC Director Rochelle P. Walensky, MD, MPH, said during a White House press briefing, although she added that trends vary by location.

Rochelle Walensky

“These new reports show the importance of being up to date with COVID-19 vaccinations,” Walensky said.

One MMWR study included data from more than 222,000 ER and urgent care encounters and almost 88,000 hospitalizations among adults with COVID-19-like illness between Aug. 26, 2021, and Jan. 5, 2022, in 10 states.

Researchers found that overall estimated vaccine effectiveness against laboratory-confirmed COVID-19 declined during the period when omicron was the predominant circulating SARS-CoV-2 virus compared with the period dominated by the delta variant, but that receiving a booster dose increased protection.

Specifically, vaccine effectiveness against COVID-19 hospitalizations during the omicron period was 90% among people who were boosted, compared with 57% among people who were not, measured 6 months after their second dose. Getting boosted was 82% effective at preventing visits to ERs and urgent care centers, whereas getting two doses was only 38% effective at preventing those visits at 6 months post-second dose.

A second MMWR study found that people who received three shots were less likely to be infected with the omicron variant, according to data from 25 state and local health departments. The study showed that during the omicron wave, case rates were highest among the unvaccinated (725.6 cases per 100,000 people), lower for people who received a primary series with no booster (254.8 per 100,000 people) and lowest among people who received a booster (148.6 per 100,000).

The third study, published in JAMA, backed up the other findings. It showed that a third dose added protection against both the delta and omicron variants.

In that study, researchers assessed more than 13,000 cases of COVID-19 caused by omicron in the U.S. and found that people who were vaccinated and boosted with a vaccine were 66% less likely to develop a symptomatic infection compared to those who only received two shots.

Walensky said that, taken together, the studies highlight two important points people who remain unvaccinated are at a significantly higher risk for infection and severe disease, and protection against infection and hospitalization caused by the omicron variant is highest for those who are up to date on their vaccinations, meaning those who are boosted when they are eligible.

“There are still millions of people eligible for a booster dose and who have not received them,” she said. “I urge all who are eligible to get their booster dose to get them as soon as possible.”

Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases and presidential medical advisor, said the current vaccines — particularly with a booster — continue to provide strong protection against severe disease, hospitalization and death.

“Therefore, get your vaccinations up to date,” he said. “It is essential for your protection.”


Accorsi EK, et al. JAMA. 2021;doi:10.1001/jama.2022.0470.

Johnson AG, et al. MMWR Morb Mortal Wkly Rep. 2022;doi:10.15585/mmwr.mm7104e2.

Thompson MG, et al. MMWR Morb Mortal Wkly Rep. 2022;doi:10.15585/mmwr.mm7104e3.