COVID vaccines to focus on combating prevailing XBB variant

In an update released on Friday, the Food and Drug Administration (FDA) instructed vaccine manufacturers to focus on targeting the XBB.1.5 strain of omicron for their fall COVID-19 update.

According to the Centers for Disease Control and Prevention (CDC), the XBB.1.5 variant is currently responsible for approximately 40 percent of all infections.

Vaccine companies have been diligently working on the development of XBB-specific vaccines, aiming to have them ready by the end of summer. During a recent FDA advisory panel, company representatives assured that they would be able to provide XBB.1.5 vaccines earlier than vaccines targeting other potential strains.

The panel unanimously voted in favor of exclusively targeting an XBB strain during their meeting.

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The FDA’s directive on Friday marks only the second update for the COVID-19 vaccine. The initial version targeted the original strain of the virus, and the most recent update covers both the original virus and earlier omicron subvariants BA.4 and BA.5.

However, the protection provided by these vaccines against severe diseases diminishes over time, and the protection against mild illnesses was already relatively low. Additionally, the ancestral strains and the omicron subvariants are no longer circulating.

Focusing on the XBB.1.5 strain carries some risk, as the virus constantly mutates to evade immunity. It may not be the dominant strain in the upcoming autumn and winter.

This strategy is similar to how scientists develop the annual flu shot. The different strains of XBB are similar enough to each other that even if the shot isn’t an exact match, it will still offer cross-protection against severe diseases and help prevent hospitalizations.

The FDA and CDC face the challenge of determining when to advise health providers to cease administering the current version of the vaccine.

Health officials will also need to convince the public to get the new shot. Only 17 percent of Americans have received a bivalent booster dose since their rollout last year.

Data presented during the meeting on Thursday revealed a significant decline in protection against hospitalization four to six months after receiving a bivalent booster. Older adults are particularly vulnerable.