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The U.S. Food and Drug Administration (FDA) on Tuesday ended the Emergency Use Authorization for the original, monovalent COVID-19 vaccines and instead authorized the bivalent vaccine, which previously was available only as a booster, for all doses of the COVID-19 vaccine for people ages 6 months and older.

The agency also said that some people — those over age 65, some immunocompromised people and unvaccinated children — are now eligible to get another COVID-19 booster four months after their last bivalent shot.

Peter Marks, M.D., Ph.D., director of the FDA’s Center for Biologics Evaluation and Research said the change was part of an effort to simplify the vaccination process and “help encourage future vaccination.”

The FDA implemented the change after the agency’s Vaccines and Related Biological Products Advisory Committee in January voted unanimously to recommend replacing the original Pfizer and Moderna primary series mRNA COVID-19 vaccines with the bivalent boosters, despite concerns about insufficient clinical trial data to support safety and efficacy.

The FDA authorized the original vaccines in December 2020, based on clinical trial data for efficacy against the original Wuhan virus strain, although the FDA withheld much of that data from the public.

The updated “bivalent” vaccines target the original Wuhan strain, plus the BA.4 and BA.5 Omicron subvariants. But those subvariants were displaced by the XBB forms of Omicron in 2022, and aren’t present in the population now, according to the Centers for Disease Control and Prevention’s (CDC) COVID data tracker.

Regulators at the FDA and the CDC authorized and recommended the bivalent vaccines as boosters in September 2022, despite having no clinical trial data in humans to support the recommendation.

When the bivalent boosters were first authorized, Dr. Meryl Nass said it was the fastest rollout of a new vaccine in history.

The rollout was possible, Nass wrote, only “by bending the rules, creating a new regulatory playbook and failing to obtain any human data for the new vaccines.”

She added:

“The manufacturers did not have to go through months-long trials, and the FDA did not have to pore over any human trial data, because there weren’t any.

“Let that sink in: The new BA.4/5 bivalent vaccines were tested only in mice, not humans.”

Officials say the current bivalent vaccines work against other Omicron subvariants, but those claims relied on tests showing the bivalent shots trigger higher levels of neutralizing antibodies, rather than on clinical trials or real-world effectiveness data.

Vinay Prasad, M.D., MPH, pointed out that nearly all of the recommended changes announced by the FDA still lack data to support the recommendations:

“The data we have on hand shows that even the newer boosters are completely ineffective,” Peter McCullough, M.D., MPH, said in an interview posted on Twitter, adding, “They never stopped BA.4, BA.5, and since that time, the virus has mutated.”

“So at this point in time the boosters have been simplified for pharmacies and administration,” said McCullough, a cardiologist, “but I anticipate that at this time they are completely ineffective and they are just as unsafe as they have always been.”

‘Never-ending’ boosters into the future

According to the new guidelines, most people who already received a bivalent vaccine shot are not currently eligible for another.

But only 16.7% of people in the U.S. have taken a bivalent booster, compared to 69.4% who took the primary series, according to the CDC, indicating that there isn’t a lot of demand for another shot.

FDA officials said the changes were meant in part to increase vaccine uptake.

“This approach will help us achieve higher vaccination coverage across the country,” Marks told reporters. “If anything comes out of this action, we’re hoping that it can encourage people who have not received the bivalent booster to go out and consider getting one.”

The CDC’s Advisory Committee on Immunization Practices (ACIP) met on Wednesday and endorsed the FDA’s new guidelines, citing similar reasons for the changes.

The CDC said in a press release this measure would simplify the COVID-19 vaccine recommendations and allow more flexibility for older people who want the option of added protection.

There is an ample supply of vaccines. Of 171 million doses of the vaccine purchased by the Biden administration, 116 million remain unused.

“Those doses are going to be expiring and will be thrown out,” Peter Hotez, M.D., Ph.D., co-director of the Texas Children’s Hospital Center for Vaccine Development and dean of the National School of Tropical Medicine at Baylor College of Medicine, told NPR.

“So it makes sense to have those shots in arms instead of being tossed in the wastebasket.”

Hotez’ comment, and the lack of clinical trial data for approving what would be the seventh COVID-19 shot for some, led experts like Dr. Marty Makary, a public health researcher at Johns Hopkins Bloomberg School of Public Health, to question the motivation behind the “never-ending” booster strategy.

Prasad agreed:

The new vaccine recommendations are for the spring. Both agency advisory committees said they will meet in the summer to discuss fall boosters and set recommendations.

Both agencies indicated in previous advisory committee meetings and recently at the World Vaccine Congress that they likely plan to offer boosters annually or biannually into the future.