Single Dose of Omicron-Targeting Vaccines to Become Main Covid-19 Shot in U.S.

The Food and Drug Administration also authorized a second booster of the updated shots for people at high risk of Covid-19, specifically people 65 years and older or people who have weak immune systems.

The agency’s actions mark the latest tweaks to Covid-19 vaccines, and could be followed up by further efforts to simplify the complicated vaccination regimen, perhaps by enshrining plans for a once-a-year shot for most people.

“The agency believes that this approach will help encourage future vaccination,” said Dr. Peter Marks, head of the FDA’s division that oversees vaccines. “Covid-19 continues to be a very real risk for many people, and we encourage individuals to consider staying current with vaccination.”

The agency said a second booster is authorized for people 65 and older whose last booster was more than four months prior, and for immunocompromised people whose last shot was more than two months prior, with additional doses as recommended by their doctors.

The moves will have little practical impact for most people in the U.S. Relatively few people are getting vaccinated against Covid-19 for the first time, while some of those at high risk have been getting a second updated booster even though it hasn’t been cleared for such use.

The changes will make a difference, however, for people seeking their first Covid-19 vaccination going forward. They will only need to get a single dose, instead of the two doses currently recommended.

The moves may also result in more high risk people, who have been waiting for an official signoff on a second shot, getting boosters.

The Centers for Disease Control and Prevention will need to recommend the new vaccination regimen and second booster before they become widely available.

The mRNA-based Covid-19 vaccines from Pfizer Inc. and its partner BioNTech SE and from Moderna Inc. have been around since December 2020. To date, people in the U.S. seeking their first Covid-19 vaccinations have gotten two doses of the original vaccines.

Reformulated versions targeting the Omicron strain and the original strain were first released last September but only as boosters.

Federal health authorities and many doctors and scientists have encouraged people to get the updated boosters to better protect against Omicron, the dominant strain of the virus in the U.S. They say people at high risk need more frequent boosting to bolster their immune defenses.

“Boosting the severely immunocompromised and anyone over 60 at least every six months is warranted even during times of less prevalence” of Covid-19, said Dr. Jeremy Faust, an emergency physician at Brigham and Women’s Hospital and an instructor at Harvard Medical School. He is co-authoring a study that examined the medical records of Israelis who received a booster to assess their risk of later getting severe Covid-19.

A study in Italy, published in February in the medical journal Eurosurveillance, found that a second dual-target booster from Pfizer and BioNTech offered stronger protection to people 60 years and older who weren’t previously infected with Covid-19 or whose last infection was more than six months prior.

Some high-risk patients have asked for additional boosters and managed to get them without FDA’s authorization, according to doctors.

Yet uptake of the updated shots has been limited overall. Some 17% of the U.S. population received a dual-targeted or bivalent booster, compared with 70% who got the full series of initial shots, according to the CDC.

Some regions have lower vaccination rates. Just over half of people in Alabama, Mississippi and Wyoming were fully vaccinated with the initial series of shots, data from USAFacts and the CDC show.

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First-time vaccine recipients have also slowed. About 9,000 people a day are getting their first Covid-19 vaccine doses this month, according to the CDC, down from more than a million at this time two years ago.

The agency said the one-dose regimen was supported by data from England that showed adolescents who received one shot of Pfizer-BioNTech’s original vaccine had increased protection against an Omicron infection with symptoms.

The agency also said it expects that most people getting vaccinated for the first time have already been infected with the coronavirus at least once. Those antibodies can serve as a “foundation” for the dual-target shot to build upon, Dr. Marks said.

The FDA’s latest moves don’t affect less popular Covid-19 vaccines from Johnson & Johnson and Novavax Inc. that target only the original strain of the virus. They will remain available, though older versions of Pfizer-BioNTech’s and Moderna’s shots won’t, the agency said.

Children under age 5 who get the Pfizer-BioNTech vaccine and children under age 6 who receive Moderna’s will still need multiple doses of the vaccines to be considered fully vaccinated, agency officials said.

A Pfizer spokesman said the company supported the FDA’s changes.

“We will continue working closely with FDA, CDC and other public health authorities,” he said. “We anticipate another update from FDA in June that will provide further guidance on Covid-19 vaccine strains and vaccination timing for the 2023 fall and winter seasons.”