Respiratory syncytial virus, or RSV, is something many parents know as a cause of bronchiolitis, but others may not have heard of it until recently. RSV causes infections of the lungs and respiratory tract. It's common in children, but it can also infect adults.

"A very common disease, the most common reason why a child under 5 ends up in the hospital, 10% of all hospitalizations in that age group in the U.S. are due to RSV," says Dr. Robert Jacobson, medical director for Mayo Clinic's Primary Care Immunization Program.

Watch: Dr. Robert Jacobson discussed RSV.

Journalists: Broadcast-quality video is available in the downloads at the end of the post. Please courtesy: Mayo Clinic News Network. Name super/CG: Robert Jacobson, M.D./ Primary Care Immunization Program/Mayo Clinic

In adults and older, healthy children, RSV symptoms are similar to that of a common cold. However, RSV can cause severe infection in babies 12 months and younger, older adults with heart and lung disease, or anyone with a weak immune system.

"RSV in an older, frail adult is more likely to cause more morbidity and mortality than flu or COVID-19 in that age group. This is a big thing, and now we have vaccines for them," Dr. Jacobson explains.

RSV vaccines

Dr. Jacobson says, during the pandemic, testing centers would often test for RSV, along with testing for COVID-19, which provided some insight into the impact of RSV in certain populations.

"We learned how severe a disease it is for older, frail adults, so much so that companies actually developed vaccines for these older adults, and in doing so, also found a vaccine that would work well and would be safe for pregnant individuals to get to protect their babies against bronchiolitis," Dr. Jacobson says.

It’s recommended that everyone 75 and older should get the RSV vaccine. Everyone 60 and older with a chronic condition may be eligible and should talk with their care team.

There is also an RSV vaccine that is safe and recommended for pregnant people.

"If you're a pregnant individual and it's September through January, consider making antibodies you can give your baby at birth to protect them from bronchiolitis hospitalization and worse, from RSV disease," says Dr. Jacobson.

While there's not an RSV vaccine for babies, there is a passive immunization for babies whose parents were not able to get the RSV vaccine during pregnancy.

"It's not a vaccine, but it gives long-lasting immunity for a good five months. We even have it available for babies 8 months through 19 months of age who have some risk factors for serious disease," says Dr. Jacobson.

RSV season can depend on where you live. In the mainland U.S., it usually starts around November and goes through March. Timing may differ for some parts of Florida, Alaska, Hawaii, Guam, Puerto Rico and American Samoa. Parents in those areas should get information from their local public health officials on the best timing to protect their babies from RSV.

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