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Updated Bivalent COVID-19 Vaccines Protect Against XBB.1.5 Omicron Subvariant

The Centers for Disease Control and Prevention (CDC) have released new data demonstrating the efficacy of the updated bivalent COVID-19 vaccines in protecting against the XBB.1.5 omicron subvariant.[0] This subvariant is believed to be more transmissible than previous mutations, and accounts for 50 percent of current COVID-19 cases in the United States.[0]

The bivalent vaccine boosters from Pfizer and Moderna have been reported to be more effective than the monovalent mRNA boosters in preventing coronavirus infection. A November 2022 study found that the Pfizer-BioNTech bivalent booster (protecting against the original coronavirus strain and the now prevalent omicron variant) is more effective at protecting against Covid than the original monovalent vaccine.

The Food and Drug Administration (FDA) authorized the use of Moderna and Pfizer-BioNTech bivalent COVID-19 vaccines for use as a booster dose on August 31, 2022.[1] The study findings showed that bivalent booster vaccination as a fourth COVID-19 vaccine dose boosted protection against SARS-CoV-2-related hospitalization and mortality compared to triple-vaccinated individuals. Fourth dose immunization with bivalent booster vaccines provided marginally higher protection against hospitalization due to COVID-19 than bivalent booster vaccines.

Additionally, the study authors noted that the bivalent vaccines are likely to have a similar effect as boosting with monovalent vaccines, but booster dosing should be reserved for people most likely to need protection against severe disease, such as older adults, people with multiple coexisting conditions, and those who are immunocompromised.[2]

The CDC urged all people to stay up to date with recommended COVID-19 vaccines, including receiving a bivalent booster dose when they are eligible.[3] Vaccines work by reducing the odds of hospitalization, death and severe illness, and although vaccines aren’t 100% effective at preventing infection, they reduce the risk of infection and transmission.[4]

Finally, the authors noted that it is too early to know how waning will happen with the bivalent vaccine, but from past experience protection against symptomatic infection decreases over time.[5] However, protection lasts longer for more severe illness.[6] Yearly COVID vaccines will help prevent major outbreaks, and those eligible are urged to get the vaccine to reduce the risk of infection and transmission.[4]

0. “Updated vaccine doesn’t lose efficacy in preventing symptomatic COVID cases due to XBB.1.5: CDC” msnNOW, 25 Jan. 2023,

1. “Effectiveness of Bivalent Boosters against Severe Omicron Infection | NEJM”, 25 Jan. 2023,

2. “What the latest studies show — and what they don’t — about the bivalent boosters’ effectiveness”, 20 Jan. 2023,

3. “CDC report: Bivalent COVID-19 boosters still work against latest strain; local, state deaths rise”, 27 Jan. 2023,

4. “Covid Vaccines: Here’s Evidence They Work—Despite Persistent Misinformation—Along With Side Effects And Common Misconceptions” Forbes, 26 Jan. 2023,

5. “CDC study confirms booster shot effectiveness against sub-variants” UPI News, 26 Jan. 2023,

6. “New booster works against dominant Covid strain” POLITICO, 25 Jan. 2023,

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