AstraZeneca Plc and Sanofi’s drug for RSV in infants was approved in the US, the first-ever preventive intended for wide use against a common but dangerous virus in young children.

The green light from the Food and Drug Administration came ahead of the US RSV season, which normally picks up in the fall but has also surged in the spring and summer in recent years as the Covid-19 pandemic has shifted when viruses hit.

Beyfortus is a long-acting monoclonal antibody designed to prevent the lung virus in newborns and infants entering their first RSV season. It is given as a shot at birth if a baby is born either just before or during the RSV season, which normally runs from around October to March in the northern hemisphere.

Scientists and doctors have been searching for RSV vaccines and drugs for decades to tackle a disease that hospitalizes up to 80,000 children under age five every year in the US. The illness is particularly aggressive in infants and older people, killing an estimated 14,000 American adults every year.

Following research breakthroughs, a handful of new products to prevent RSV could be on the market in 2023. Shots from Pfizer Inc. and GSK Plc received backing from a panel of US health advisers last month, which recommended the vaccines in those age 60 and older after consultation with their doctors. The FDA approved those in May. Pfizer is also awaiting approval for its vaccine to be used in pregnant women to protect young babies.

RSV prevention in newborns in the US and EU could generate $1.3 billion in 2032 sales, according to an analysis by Bloomberg Intelligence. This would be shared between Pfizer’s maternal vaccine and Sanofi and Astra’s medication.

After the approval, it’s up to advisers to the Centers for Disease Control and Prevention to decide how Sanofi and Astra’s drug will be used. Experts raised concerns about the rate of preterm birth in the pregnant people who’d gotten the Pfizer shot in a hearing in May.

Regulators and governments will also need to decide whether Pfizer’s vaccine and Astra and Sanofi’s antibody should both be given to pregnant people and their babies. A committee of FDA advisers agreed Pfizer’s vaccine was effective against severe RSV for the first six months of life.

Before the recent breakthroughs, Astra had an older RSV drug that was a form of immunization for infants at risk of severe disease, such as premature babies. The antibody provides only short-term protection and requires multiple injections.

--With assistance from Nacha Cattan.