Enlarge / Vials with COVID-19 vaccine labels showing logos of pharmaceutical company Pfizer and German biotechnology company BioNTech. (credit: Getty | Photonews )

An advisory committee for the Food and Drug Administration on Thursday voted unanimously (21 to 0) to recommend updating COVID-19 vaccines for the 2023-2024 period to be a monovalent formula targeting the latest omicron subvariant lineage of XBB. Such an update would apply to both primary series shots as well as boosters.

The monovalent update means that the next COVID-19 vaccines will only target one version of pandemic coronaviruses. This is a switch from the current formula, which is bivalent, targeting both the spike protein from the ancestral SARS-CoV-2 strain and the previous leading omicron subvariants BA.4/5 (which share a spike protein).

In Thursday's day-long meeting, advisors reviewed data suggesting that the current bivalent vaccine continues to protect from the most severe outcomes of COVID-19, but protection from infection and hospitalization wanes over time and wanes notably faster against the XBB variants. To date, only 17 percent of Americans have received a bivalent booster, meaning their protection is significantly weakened since their last dose of the original vaccine formula, which only targeted the ancestral strain.

Enlarge / Revelers celebrate New Year’s Eve in Times Square on January 1, 2023, in New York City. This year's New Year's Eve returned to pre-COVID-19 pandemic numbers, with around 1 million people estimated to fill Times Square. (credit: Getty | Alexi Rosenfeld )

A new omicron coronavirus subvariant dubbed XBB.1.5 now accounts for an estimated 40.5 percent of all US COVID-19 cases amid a winter wave that is driving up hospitalizations, particularly in places where XBB.1.5 is most prevalent.

Nationwide, new reported cases are hovering around 59,000 per day, which is still relatively low compared with previous waves. But case data has become murkier over the 3-year-old pandemic, with fewer testing sites available now and the results of common at-home tests going unreported. Additionally, data reporting generally lags around end-of-year holidays, meaning case reports may jump in the coming days as backlogged data rolls in.

Hospitalizations, however, are clearly rising, with an average of around 45,000 hospitalized per day, according to data tracking by The New York Times. National hospitalization rates now rival those from the peak over this past summer driven by bygone omicron subvariants, federal data shows. Some of the areas seeing the large upticks in hospitalizations are those where the new subvariant, XBB.1.5 is most prevalent. For instance, in the Northeast (federal health region 1), XBB.1.5 has the highest regional proportion, accounting for 75 percent of cases, and hospitalizations have risen 16 percent over the prior seven days, the largest region-specific rise, according to data from the Centers for Disease Control and Prevention.

Enlarge / US President Joe Biden receives the latest COVID-19 booster shot in the South Court Auditorium of the Eisenhower Executive Office Building, next to the White House, in Washington, DC, on October 25, 2022. (credit: Getty | Saul Loeb )

The Biden administration is struggling to refocus the country's attention back on the pandemic as the fall booster campaign drags and the latest models project that tens of thousands of Americans will needlessly die this winter of COVID-19.

“This year, nearly every [COVID-19] death is preventable," President Biden said Tuesday just before rolling up his sleeve to receive his own updated COVID-19 booster.

Few Americans are following his lead. The White House has pushed Halloween as a soft deadline for Americans to get their updated, bivalent COVID-19 booster, arguing that such timing of the dose will allow for the immune system to mount maximal antibody and other immune responses before Americans begin gathering for fall and winter holidays, such as Thanksgiving, when transmission risks increase. But, with Halloween just days away, only 19.4 million Americans have received a bivalent booster—that's just 6 percent of the people eligible for the shot, which is free and available to everyone ages 5 and above.