After six decades of research marked by setback after setback, scientists have chalked up a big win against RSV (respiratory syncytial virus): On May 31 the U.S. Food and Drug Administration (FDA) approved a vaccine from Pfizer aimed at preventing potentially dangerous complications from RSV in adults age 60 and older.
The approval of this RSV vaccine, called Abrysvo, comes less than a month after the FDA green-lighted the world’s first RSV vaccine, Arexvy, from GlaxoSmithKline (GSK).
“A vaccine to help prevent RSV had been an elusive public health goal for more than half a century,” said Annaliesa Anderson, PhD, the senior vice president and chief scientific officer of vaccine research and development at Pfizer in a statement. “Abrysvo will address a need to help protect older adults against the potentially serious consequences of RSV disease.”
Together, the new RSV vaccines represent a major breakthrough in protecting older people against this highly contagious virus. Seniors are particularly vulnerable to severe disease caused by RSV, as are infants and people who are immunocompromised.
The Centers for Disease Control and Prevention (CDC) estimates that RSV leads to 60,000 to 160,000 hospitalizations annually among adults age 65 and up. About 6,000 to 10,000 seniors die each year from RSV-related lower respiratory tract disease.
“These high numbers may seem surprising to some as we often do not hear much about RSV in older adults,” says Beth Thielen, MD, PhD, an assistant professor at the University of Minnesota Medical School in Minneapolis. “Because we have had no specific treatments for RSV in older adults, healthcare providers have often been discouraged from sending [them for] testing for RSV, so it is almost certainly underdiagnosed.”
Pfizer’s Vaccine Was Highly Effective in Studies
The Pfizer shot was shown in late-stage trials to be more than 85 percent effective against severe illness caused by RSV, and nearly 67 percent effective in preventing lower respiratory tract illness overall.
These research results were based on data from more than 37,000 adults ages 60 and older.
The GSK and Pfizer vaccines work on a similar principle. Both trigger a highly protective response to RSV by targeting a part of the virus, called pre-fusion F protein, that allows it to attach to and infect human cells.
“The vaccine causes the body to make antibodies that bind to the F protein on the surface of the virus,” says Dr. Thielen. “This F protein is critical to allowing the virus to get into cells to infect them, so if there is a binding antibody attached to that protein, it doesn’t allow the virus to get in the cells.”
There are two major subtypes of RSV (A and B). Both circulate during the same season, but in general, one predominates. Unlike GSK’s vaccine, Pfizer’s product is a bivalent one that has elements specifically targeting A and B strains of RSV.
In contrast to the Pfizer vaccine, the GSK shot contains an adjuvant, a drug designed to make the vaccine more potent.
Pfizer and GSK’s vaccines have proved to be highly effective against both RSV strains, with minimal side effects (mainly pain at the injection site, swelling, and fatigue).
“There have been a few cases of a heart condition called atrial fibrillation and a neurological condition called Guillain-Barré syndrome in study participants who received the vaccines,” says Thielen. “These were rare events, and more study will be needed in larger populations to determine whether this is truly related to the vaccines.”
A Common Virus Can Cause Severe Problems
RSV is a very common respiratory virus that usually produces mild, cold-like symptoms, which pass in a week or two. Typical symptoms are a runny nose, decreased appetite, coughing, sneezing, fever, and wheezing.
Most individuals can get over the illness at home by getting plenty of rest and fluids, and taking over-the-counter fever reducers, such as acetaminophen or ibuprofen.
In older adults and other vulnerable populations, the physical effects from the virus can be extreme and even life-threatening. Some patients require intensive care if they develop bronchiolitis (inflammation of the small airways, or bronchioles, in the lungs) or pneumonia (infection of the lungs).
The virus is so widespread that almost everyone has been infected by their 2nd birthday, according to the Centers for Disease Control and Prevention (CDC). People can get the virus repeatedly during their lifetime.
“We know that people can get reinfected multiple times,” says Thielen. “Immunity wanes in older adults, so we see more severe disease in them and in the immunocompromised.”
If patients are having great difficulty breathing or have become dehydrated, they may need to be hospitalized to receive additional oxygen, IV fluids, or in the most dire circumstances intubation (a breathing tube inserted through the mouth and down to the airway) with mechanical ventilation (a machine to help a person breathe). In most cases, hospitalization only lasts a few days.
How Much Will the New RSV Vaccines Cost?
Pfizer and GSK both anticipate the shots to cost nothing or little for most seniors.
“The recently enacted Inflation Reduction Act will significantly help eliminate access barriers as it allows for $0 copays for necessary adult vaccines under Medicaid and Medicare Part D,” says Keanna Ghazvini, a spokesperson for Pfizer.
An RSV Shot to Protect Infants May Be Next
While the recent FDA approvals are good news for seniors, there is currently no RSV vaccine for infants. But Pfizer is hoping the FDA will approve its RSV vaccine as a maternal immunization, meaning pregnant women would get the shot and pass protective antibodies to their babies in utero.
An FDA decision on this use is expected in August.
