The Food and Drug Administration on Wednesday approved the latest round of Covid vaccines in the U.S., but set new limits on who can get them.

The agency ended its broader authorization of the shots, only clearing them for people at higher risk of severe illness. That includes those 65 and up and younger adults with at least one underlying condition that puts them at higher risk.

The move could complicate access to the shots for millions of Americans, and raises questions about whether insurance plans will still cover them for healthy adults.

“The emergency use authorizations for Covid vaccines, once used to justify broad mandates on the general public during the Biden administration, are now rescinded,” Health and Human Services Secretary Robert F. Kennedy Jr. said in a post on X.

“The American people demanded science, safety, and common sense,” he said. “This framework delivers all three.”

It follows several efforts by Kennedy, a prominent vaccine skeptic, to change immunizations in the U.S. The new limited authorizations are a break from U.S. vaccine policy in previous years, which recommended an annual Covid shot for all Americans 6 months and up.

A key panel of vaccine advisors to the Centers for Disease Control and Prevention must vote to recommend the Covid shots. But Kennedy earlier this year gutted that panel and named new members, some of whom are widely known vaccine critics.

In the post, Kennedy said the shots are available for all patients who choose them after consulting with their doctors. But it’s unclear how easily patients without high-risk factors will be able to get a Covid vaccine.

Kennedy said the FDA has authorized Moderna‘s shot for those 6 months and up, Pfizer‘s vaccine for people ages 5 and up, and Novavax‘s jab for those ages 12 and up, but only for those specifically at higher risk of getting severely sick from the virus.

Adults ages 65 and up are at higher risk of severe Covid, and so are younger adults who are immunocompromised or have underlying medical conditions such as cancer, obesity, diabetes, chronic kidney disease and heart diseases, according to the CDC‘s website.

The end of the so-called emergency use authorizations means that Pfizer’s shot is no longer cleared for children ages 6 months to 4 years. It comes after Pfizer in August said it has requested that the FDA keep that authorization in place for the upcoming fall and winter season.

In a release, Pfizer confirmed that the FDA had cleared its updated Covid shot for use in adults 65 and above and those ages five through 64 with at least one underlying condition that puts them at high risk for severe illness. The company will begin shipping the shot immediately, and it will be available in pharmacies, hospitals and clinics nationwide “in the coming days.”

In a separate release, Moderna also confirmed that its updated Covid shot is approved for those 65 and up and people 6 months through 64 years of age who are at higher risk of severe illness. The company added that its new, next-generation Covid vaccine is approved for older adults and high-risk patients ages 12 through 64. Moderna said it expects the shots to be available in the coming days.

Shares of Pfizer and Moderna were trading slightly higher Wednesday afternoon, while Novavax shares dipped.

In May, the CDC dropped the recommendation that pregnant women and healthy children receive Covid shots. But the American Academy of Pediatrics diverged from the agency earlier this month, recommending Covid shots for children between 6 months and 2 years old.

In a statement on Wednesday, Dr. Susan Kressly, president of the American Academy of Pediatrics, called the FDA’s more limited approval “deeply troubling.” She said respiratory illnesses like Covid can be “especially risky for infants and toddlers, whose airways and lungs are small and still developing.”

“Any parent who wants their child vaccinated should have access to this vaccine,” she said. “Today’s unprecedented action from HHS not only prevents this option for many families, but adds further confusion and stress for parents trying to make the best choices for their children.”

She said the AAP urges the administration to “allow these choices to remain with medical experts and families.”

The American College of Obstetricians and Gynecologists also advised pregnant women to get the Covid vaccine to protect themselves and their infants, who cannot be immunized until they are 6 months old.