[Originally published: July 24, 2023. Updated: Sept. 25, 2023]
This winter, when the usual sneezing, wheezing, coughing, and fevers start up, there will be extra protection for people at high risk from at least one common illness. Respiratory syncytial virus (RSV) causes mild cold symptoms in most people but can lead to hospitalization and even death in older people and babies. But now, there are new immunizations aimed at older people, babies, and pregnant women who want to protect their newborns.
“A lot is changing for RSV,” says Scott Roberts, MD, a Yale Medicine infectious diseases specialist. “There have been attempts to make a vaccine for decades, and they have failed for a variety of reasons.”
One turning point came with the investigation of an RSV protein called “RSV fusion (F)” that provided potent stimulation to the immune system—research that paved the way to clinical trials showing positive results.
New vaccines for older people are important, partly because immunity wanes with age, and they’re unable to fight off infections, such as RSV, as well as they did when they were younger, explains Dr. Roberts. Children are vulnerable because their lungs are smaller, making them more vulnerable to severe disease. The pandemic made RSV worse for both of these groups, leading to several years of lost immunity when RSV wasn’t really circulating as people were wearing masks and taking other precautions to protect against COVID-19.
But, by November 2022, RSV was surging back in children, and the hospitalization rate for older adults was 10 times higher than usual for that time of year.
In June 2023, the Centers for Disease Control and Prevention (CDC) confirmed the Food and Drug Administration (FDA)’s approval of two vaccines for older people, specifying that those ages 60 and older “may” get them based on “shared clinical decision-making,” meaning they may receive a single dose based on discussions with their health care provider about whether RSV vaccination is right for them.
This summer, the FDA also approved two options for infants and toddlers. In August, the CDC signed off on a monoclonal antibody called nirsevimab (brand name Beyfortus™) for all infants up to 8 months old, born during—or entering—their first RSV season, and for a small group during their second season who are between 8 and 19 months old and at high risk for severe disease (including children who are severely immunocompromised).
In September, the CDC approved Abrysvo™ to be given to pregnant women ahead of the RSV season to provide them with antibodies they could pass along to the fetus and protect their newborn babies from birth to 6 months of age from severe RSV.
Dr. Roberts and Thomas Murray, MD, PhD, a Yale Medicine pediatric infectious diseases specialist, answered questions about the new options for older adults and kids.
What is RSV, and why is it a threat to some people?
RSV is a common respiratory virus that usually causes mild, cold-like symptoms. It’s a seasonal illness, typically starting in the fall and peaking in the winter. Once a person is infected, the treatment is supportive care, such as over-the-counter medications and maintaining hydration. Most people get better in a week or two.
But when RSV makes its way down into the lungs, causing lower respiratory tract disease (LRTD), it can cause vulnerable people, including those 65 and older, to develop life-threatening complications, such as pneumonia, and make existing conditions, such as asthma, congestive heart failure, and chronic obstructive pulmonary disease (COPD), worse. Each year, this leads to 60,000 and 160,000 RSV hospitalizations in adults 65 and older, and 6,000 to 10,000 deaths.
Babies are susceptible to RSV because their immune systems are not fully formed, adds Dr. Murray. “Their lungs aren't fully developed. So, if the virus gets into the lungs of really young babies, they can develop respiratory problems and need support, such as supplemental oxygen, to help them breathe.”
In children younger than 5, there are approximately 2.1 million RSV-related outpatient visits a year, 58,000 to 80,000 hospitalizations, and 100 to 300 deaths.
How effective are the RSV vaccines for older adults?
Both vaccines for older adults use traditional platforms—similar to a flu shot (and not to be confused with the mRNA technology introduced by Pfizer-BioNTech and Moderna to prevent COVID-19). The RSV vaccines work by introducing an inactivated RSV protein into the body, where it fuses to host cells and stimulates the immune system to recognize the actual RSV virus if/when it encounters it and help prevent severe disease.
Both vaccines performed well in clinical trials, according to data presented to the FDA. Arexvy™, developed by GSK, was the first to receive FDA approval—in early May—based on data from a trial conducted by the company in the U.S. and internationally. The ongoing trial is following participants through three RSV seasons. In late June, GSK reported an overall efficacy of 82.6% against lower respiratory tract disease during the first season, 77.3% for mid-season, and 67.2% over two seasons. Against severe disease, efficacy was 94.1% during the first season, 84.6% at mid-season, and 78.8% over two seasons.
The second vaccine, called Abrysvo™, from Pfizer, showed an efficacy of almost 89% against LRTD involving at least three symptoms in the first year after vaccination, and 78.6% mid-way through a second season in the data presented to the FDA. LRTD symptoms include new or increased cough, wheezing, sputum (phlegm) production, shortness of breath, and/or tachypnea (abnormally rapid breathing).
While data showed that one vaccination could be protective for at least two seasons, no determination has been made on how frequently the shots should be given.
Will there be an RSV vaccine available for children?
In September, the CDC approved Abrysvo on a seasonal basis to provide pregnant women with antibodies they could pass along to the fetus and protect their newborn babies from birth to 6 months of age from severe RSV. Pregnant women can get a single dose at 32 to 36 weeks of gestational age.
The vaccine is available from September to January to provide protection of newborns when infection rates are expected to be at their highest, between October and March. The shot is not recommended from February through August. The CDC says most infants will need protection from one of the new RSV immunizations—either the monoclonal antibody or the vaccine.
Abrysvo has been shown to reduce the risk of RSV hospitalization for babies by 57% in the first six months after birth, according the CDC.
What do we know about nirsevimab, the FDA-approved monoclonal antibody for infants and toddlers?
Nirsevimab, which was developed by Sanofi and AstraZeneca, is given in a single injection to the thigh. A Phase 3 clinical trial showed that nirsevimab reduced RSV-triggered lower respiratory tract infections serious enough to require medical care by 76.4% and cut RSV hospitalizations in healthy full-term and near-full-term infants by 76.8%.
The monoclonal antibody works differently than a vaccine. “When you're injected with a vaccine, it causes your body to produce antibodies to protect you against whatever the vaccine is for,” Dr. Murray says. “The monoclonal antibody bypasses that step. Your body gets—in this case—a single kind of antibody directly injected into the bloodstream so that if you're infected with that organism, the antibodies will bind to it and help you clear the infection.”
The antibody reduces hospitalization significantly, he adds. "Even if it doesn't completely prevent disease, it can significantly reduce disease severity. This will be extremely helpful this year, especially after the RSV surge we had last winter,” he says. “And in the trials, there was no difference in adverse effects between the placebo and antibody groups.”
What if you are not an older person or an infant?
If you don’t fall into one of those categories and are otherwise healthy, you probably don’t need a preventive therapy, Dr. Murray explains. “Virtually every child has experienced RSV by the age of 2 and has immunity,” he says.
Older children, teenagers, and most adults have strong immunity from multiple exposures and rarely experience LRTD from RSV. “We want to make things available to the highest-risk patients first,” Dr. Murray says. “We'll have to wait and see whether or not the vaccines will be approved for people at other ages with chronic underlying illnesses, such as serious heart or lung problems.”
Are there side effects from the vaccines or other concerns?
The CDC advisory panel expressed concerns about the clinical trial data to the point where they changed an initially strong recommendation to get the vaccine, if eligible, to one that says people over 60 “may” get an RSV vaccine based on a shared discussion with their doctors. For some, this may mean a discussion with their pharmacist. (The RSV vaccines will be covered by Medicare Part D and, thus, will be administered in pharmacies in many cases.)
One issue was that a few people in the trials developed Guillain-Barré syndrome in the days following the shot. Guillain-Barré is a rare disorder that causes muscle weakness and sometimes paralysis.
In addition, atrial fibrillation (an arrhythmia that can lead to blood clots in the heart) within 30 days of vaccination was reported in 10 participants who received Arexvy and four participants who received a placebo.
“One could argue that the benefits of these vaccines far outweigh the risks; for instance, the protection afforded against severe RSV disease is greater than the small risk of Guillain-Barré in this situation,” says Dr. Roberts. There will be continued monitoring for Guillain-Barré and other issues once the RSV vaccines become available, he adds.
Another issue was that most of the participants in the clinical trials were in their 60s, so there was little data on other high-risk groups, such as those over age 80.
Should you get the RSV vaccine if you’re eligible?
Both doctors say the benefits of the new vaccines for older adults outweigh the potential harms in cases where RSV could be life-threatening. They recommend them to all eligible older adults, particularly those with underlying health conditions, such as heart or lung disease, or weakened immune systems.
They also suggest that people who are vulnerable or could infect others who are at high risk take additional precautions this fall. RSV is spread through direct contact with the virus, whether that's from droplets from another person's cough of sneeze, or from touching a contaminated surface. The CDC recommends covering coughs and sneezes with a tissue or shirt sleeve (not your hands), washing hands often, keeping hands away from your face, avoiding kissing and other close contact with people who have cold-like symptoms, cleaning frequently touched surfaces, such as doorknobs and mobile devices, and staying home when you are sick. Some experts advise wearing a mask depending on your risk for serious disease. “All of these things will protect against RSV,” Dr. Roberts says.