Pfizer says it has made an RSV vaccine that protects newborns against severe illness — and will file for FDA approval within weeks

• A groundbreaking RSV vaccine for newborns appears to protect babies well against severe illness.
• RSV can be dangerous for newborns, causing pneumonia and, in severe cases, death.

A new vaccine designed to protect newborns against respiratory syncytial virus (RSV) worked well in clinical trials, according to its maker — a promising step towards a first-of-its kind shot that could be a lifesaver.

Pfizer announced on Tuesday that its RSV vaccine candidate, RSVpreF, was 81.8% effective at protecting babies from severe cases of the respiratory illness in their first three months of life, and 69.4% effective for six months.

The company is planning to file regulatory paperwork in the US by the end of 2022, meaning that — if all goes well — this new vaccine could be available to pregnant people some time next year. (On average, it takes about eight to ten months for the US Food and Drug Administration to make a decision about new vaccines, after company paperwork is filed.)

The news comes as pediatric RSV hospital admissions soar across the US. RSV is hitting babies early and hard this year, with some needing intensive care treatment, including help breathing, and suctioning out their mucus. There is currently no vaccine or treatment for RSV.

"I just have to help the kids through, and give their bodies time to fight this virus," Dr. Melanie Kitagawa, medical director of the pediatric intensive care unit at Texas Children's Hospital, recently told Insider.

A single shot for pregnant people, around the third trimester

Pfizer's RSV vaccine is administered as a single shot for pregnant people, given during the late second or third term of pregnancy. The shot is designed to protect little ones in a similar way to how natural immunity for RSV works.

People who have recently had an RSV infection (or, in the case of this trial, a vaccine) can pass so-called maternal antibodies on to their baby in the uterus, and also during breastfeeding. That immunity is critical for little ones in their first months of life. When babies' airways are small, an RSV infection can make it difficult to breathe, as the respiratory tract clogs with mucus, and children cough and wheeze.

For decades, the advice from doctors has been little more than "watch them closely" and"call me if they get worse," pediatrician Daniel Leonard previously told Insider. On average, between 100 to 500 children under the age of 5 in the US will die from the illness every year, according to the Centers for Disease Control and Prevention. A vaccine could remedy that issue.

Pfizer is also working on an RSV vaccine for adults aged 60 and up, who — like babies — can suffer severe consequences of RSV, including pneumonia and death.

"We look forward to working with the FDA and other regulatory agencies to bring this vaccine candidate to expectant mothers, to help protect their infants against severe RSV during their most vulnerable first six months of life," Annaliesa Anderson, Pfizer's chief scientific officer for vaccine research and development, said on Tuesday in a release.