Updated Booster Dramatically Reduces Risk for COVID Death: Study

Lisa O'Mary

February 13, 2023

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A new CDC study shows that people who got the updated bivalent COVID-19 booster by the end of last year were 14 times less likely to die from the disease than people who were never vaccinated, and three times less likely to die from the disease than those who got only the original vaccines.

Older adults saw the biggest boost of protection from the bivalent booster. The study also offered evidence that the bivalent booster's protection begins to wear off after 2 months.

"When compared with unvaccinated persons, persons who had received bivalent boosters were provided additional protection against death over monovalent doses or monovalent boosters," the study authors write. 

The study was published Friday by the CDC and evaluated the effectiveness of vaccination and boosters in people age 12 and older using COVID case and death counts between Oct. 3, 2021, and Dec. 24, 2022. During that time, the two dominant strains of the virus were Delta and the Omicron subvariants BA.2, BA.4, and BA.5. The latter two strains accounted for 78% of cases as of the end of the study period.

In all, researchers analyzed data for more than 21 million COVID cases and 115,078 associated deaths. The data came from 23 states plus Washington, D.C., which were selected because they could provide linked data on cases, vaccinations, and deaths.

Throughout the duration of the study period, unvaccinated people were more likely to get COVID or die from it than people who got the monovalent-only booster. People who got the bivalent booster were significantly less likely to die from COVID than people who only got monovalent boosters.

The CDC authorized the bivalent booster Sept. 1, 2022. The bivalent booster is an updated version of its predecessor (the monovalent booster) and was designed to better address the BA.4 and BA.5 strains of COVID. The authors write that 17.5% of people ages 12 and older had received the bivalent booster at time of publication.

The Omicron strains that were widely circulating during the study now account for less than 1% of cases, according to CDC estimates. The current predominant strain is XBB.1.5, and there is some initial evidence that the bivalent booster offers protection from severe COVID or death during the XBB.1.5 era.

In light of the new CDC study's findings, the authors recommend that "all persons should stay up to date with COVID-19 vaccination, including receipt of a bivalent booster by eligible persons, to reduce the risk for severe COVID-19."


CDC: "COVID-19 Incidence and Mortality Among Unvaccinated and Vaccinated Persons Aged ≥12 Years by Receipt of Bivalent Booster Doses and Time Since Vaccination — 24 U.S. Jurisdictions, October 3, 2021–December 24, 2022," "COVID Data Tracker Variant Proportions."

TIME: "The Bivalent Booster Protects Against New COVID-19 Variants, New Data Show."


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