FDA Committee Recommends COVID-19 Vaccines Should Be Monovalent, Contain the XBB Strain


The FDA committee, known as VRBPAC, in charge of evaluating vaccines and related biological products recently voted unanimously that the upcoming 2023-2024 COVID-19 vaccines should be updated with a monovalent XBB strain.

Food and Drug Administration  (Adobe Stock, unknown)

Food and Drug Administration

(Adobe Stock, unknown)

This article first appeared on ContagionLive.com.

Today, the US Food and Drug Administration’s (FDA) Vaccines and Related Biological Products Advisory Committee (VRBPAC) met in an open session to discuss and recommend the strains included in updated COVID-19 vaccines for the 2023-2024 vaccination campaign.

Just after 4 pm, VRBPAC voted on the following question: “For the 2023-2024 Formula of COVID-19 vaccines in the US, does the committee recommend an update of the current vaccine composition to a monovalent XBB-lineage?”

After all 21 VRBPAC members voted “Yes,” the committee moved on to their primary discussion topic: “Based on the evidence and other considerations presented, please discuss a selection of a specific XBB lineage (eg XBB.1.5 or XBB.1.16 or XBB.2.3) for inclusion in the 2023-2024 Formula of COVID-19 vaccines in the US.”

Over the course of a day-long meeting, CBER viewed and responded to presentations from the FDA, CDC, World Health Organization (WHO), Moderna, Pfizer, and Novavax, as well as hearing opinions from speakers during an open public forum.

VRBPAC had previously voted to move toward a unified strain composition for COVID-19 primary and booster vaccines on January 26, 2023. The committee aimed to provide more transparent information to the public and health care providers by simplifying strain composition. Additionally, the COVID-19 virus has evolved so significantly that there is no longer a need to include the original, wild-type Wuhan strain in the next generation of vaccines.

By the spring of 2023, virus surveillance revealed that the XBB sublineages were the predominant COVID-19 strains in the US and the world. The XBB parent lineage is a recombinant of BA.2.10.1 and BA.2.75 sublineages, indicating that we may expect more recombination variants in the future. Recombination occurs during virus replication when a cell is infected by more than 1 variant.

By June 2023, XBB sublineages accounted for over 95% of the world’s circulating COVID-19 variants. “The current trajectory of virus evolution indicates that XBB will likely be the progenitor of SARS-CoV-2 variants in the near future,” the FDA wrote in a briefing document. “XBB descendent lineages are highly immune evasive. To improve protection, particularly against symptomatic disease, COVID-19 vaccines should induce antibodies that neutralize XBB descendent lineage viruses.”

The director of the FDA Office of Vaccines Research and Review, David Kaslow, MD, reiterated this during the meeting. “First, we need a periodic update. Second, it’s time to move from the current bivalent to a monovalent.” He noted that we might shift to a bivalent strain composition in the future, but that current evidence suggests the need for a monovalent COVID-19 vaccine of the XBB lineage.

The FDA will seriously consider VRBPAC’s recommendation before relaying their official 2023-2024 COVID-19 vaccine composition guidelines to vaccine manufacturers.

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