R.S.V. Season Is Approaching. Here’s How to Protect Yourself.

Well|R.S.V. Season Is Approaching. Here’s How to Protect Yourself.

Respiratory syncytial virus, known as R.S.V., is one of the world’s most common respiratory illnesses and the leading reason infants go to the hospital in the United States.

It infects roughly 64 million people around the world each year. In the United States, it sends tens of thousands of children to the hospital annually and kills as many as 10,000 adults aged 65 and older.

R.S.V. typically begins spreading in the fall, with cases peaking around mid-winter. And it can be a “mean virus,” said Dr. Sean Liu, an associate professor of infectious diseases at the Icahn School of Medicine at Mount Sinai in New York City.

Most people who get infected develop fairly mild symptoms, which can include coughing and wheezing, a runny nose, fever, loss of appetite and congestion. But adults 75 and older and babies are at higher risk of getting seriously sick. People with compromised immune systems and underlying chronic conditions are also more likely to die from the virus.

While most people recover at home, patients with severe cases are hospitalized and may receive supplemental oxygen and IV fluids.

There are more options than ever to guard against the virus. Over the last several years, the Food and Drug Administration has approved vaccines for adults and monoclonal antibodies for infants that defend against the disease — although insurance hurdles and supply challenges have at times constrained people’s ability to access them. And many patients might have been unaware that they were even eligible, said Dr. Peter Chin-Hong, an infectious disease specialist at the University of California, San Francisco. As of this past spring, only around half of U.S. adults 75 and older had gotten vaccinated.

“The rollout wasn’t quite what we were hoping,” said Dr. Seth Cohen, the medical director of infection prevention at the University of Washington Medical Center. “This year is really the first time where it feels like we can be not just reactive, but really trying to prevent a lot of these infections.”

What to know about R.S.V. vaccines for adults.

The Centers for Disease Control and Prevention recommends that adults 75 and older get vaccinated against R.S.V.

The agency’s latest guidelines also urge people 50 and older to get vaccinated if they are at higher risk for getting very sick. This includes those who live in nursing homes or have conditions like chronic heart, lung and liver disease; compromised immune systems; severe obesity; or diabetes with accompanying organ damage. (Previously the agency recommended that people who are at higher risk get the shot if they are 60 and older. The C.D.C. quietly broadened its guidance this summer.)

In January, the F.D.A. added a warning to the labels of some R.S.V. vaccines about a possible link between the shots and Guillain-Barré syndrome, a rare autoimmune condition that can cause nerve damage. Federal health officials found that R.S.V. vaccines might have caused a small number of cases of Guillain-Barré — around two per 100,000 vaccinated people. However, it isn’t clear that the vaccines themselves caused the syndrome, and officials have said that more data was needed to determine the risk.

“It's really tricky to interpret those very, very small numbers of a very rare event,” Dr. Cohen said. And the benefits of protection, he added, outweigh the potential risk of Guillain-Barré syndrome in people who are eligible for the R.S.V. vaccination.

Doctors generally recommend that people get vaccinated in the late summer or early fall, so that there’s time for antibodies to kick in before cases spread. There are three vaccines available, all of which lower the risk of hospitalization and serious illness.

If you’ve already gotten vaccinated against R.S.V., you do not need another shot. Current data shows that vaccines offer protection for at least two years; it’s not yet clear whether protection could last even longer, said Dr. Chin-Hong.

What to know about R.S.V. vaccines for children.

Nearly every child will contract R.S.V. by the time they reach age two, but the virus can be especially dangerous for infants. Around two to three out of every 100 babies under 6 months are hospitalized with the virus each year in the United States. Some babies, including those who were born prematurely, are at higher risk for severe illness.

There are two ways to protect babies: vaccinating pregnant mothers or giving infants monoclonal antibodies.

Health officials recommend that pregnant women get one dose of a vaccine against R.S.V. if their final trimester (specifically, between weeks 32 and 36) falls between September and January, when the virus is circulating, so that they can pass on antibodies. This protects babies for roughly six months after they are born.

Pregnant women whose third trimester falls outside of those months may not need to get vaccinated for R.S.V. Instead, doctors recommend that those babies get a monoclonal antibody shot shortly before or during their first R.S.V. season, to mimic the immune system’s response to an infection. There are two monoclonal antibody shots available for infants under 8 months, one of which the F.D.A. approved this summer.

What if I’m not eligible for vaccination?

Those who are not in groups recommended for vaccination can still take steps to stay safe. The virus can spread when people who are infected cough or sneeze; droplets can also linger on surfaces. Frequently washing hands with soap and water, disinfecting surfaces like door knobs and maintaining good ventilation in enclosed spaces can help stop the spread, as can limiting contact with people who are experiencing respiratory symptoms, Dr. Liu said.

And if you’re feeling sick, consider seeing a doctor, and stay home as much as you can.