WASHINGTON (AP) — Food and Drug Administration officials have opened a safety review of two injectable drugs used to protect babies and toddlers from RSV, the respiratory virus that sends thousands of American children to the hospital each year.

The long-acting drugs from Merck and Sanofi are not vaccines, but the government review comes as health officials and advisers under Health Secretary Robert F. Kennedy Jr. roll back recommendations on routine childhood vaccinations.

A spokesman for Kennedy described the inquiry as a routine safety evaluation and said the FDA “will update product labeling if warranted by the totality of the evidence.”

The two drugmakers said in separate statements that they haven’t seen any new safety signals with their medications, which were approved in recent years for infants and young children facing RSV.

News of the review was first reported by Reuters.

The drugs are essentially laboratory-made versions of natural antibodies that help the immune system fight off RSV. The FDA has approved vaccines for older patients and pregnant women but not babies or children, making the injections a first-line treatment for youngsters against the seasonal virus.

A spokesperson for Merck, maker of Enflonsia, said company representatives met with the FDA last week.

“We expect questions from the FDA, and we want them to ask,” the company said. “We believe deeply in the importance of transparency and we value the FDA’s rigorous review of our clinical data of all of our products.”

Merck’s injection is approved to protect babies before or during their first RSV season, which typically lasts five months.

A spokesperson for Sanofi said it regularly submits any potential safety concerns to the FDA for review, but hasn’t seen any new signals with its drug across more than 50 studies.

“At this time, no safety issue has been identified from clinical studies of (Beyfortus) or from post-marketing experience with more than 6 million babies immunized worldwide,” the company said in a statement.

An infection with RSV is a coldlike nuisance for most healthy people, but it can be life-threatening for the very young and the elderly.

In 2023, Centers for Disease Control and Prevention advisers recommended the antibody shots for infants born just before or during the RSV season — if the birth mother wasn’t vaccinated late in pregnancy. The panel also recommended a dose for some 8- to 19-month-olds at higher risk of a serious illness from RSV.

Since taking over the Department of Health and Human Services, Kennedy replaced every member of the CDC committee, which also makes vaccine recommendations.

Last week, the panel urged an end to routine newborn vaccination against hepatitis B, a virus that can cause liver failure or liver cancer. The decision triggered swift backlash from numerous medical and scientific professional societies.

Separately, officials at the FDA have been scrutinizing the safety of vaccines, particularly COVID-19 shots, and floated plans for a wholesale overhaul of the agency’s decades-old approach to approving and reviewing vaccines.

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