Older people have vaccines available to prevent severe influenza and COVID-19, but there's been nothing to protect against the third respiratory virus that contributed to this season's wretched “triple-demic.”
Two major pharmaceutical companies published clinical trial results this week that pave the way for an RSV (respiratory syncytial virus) vaccine to be available for adults by the time next cold and flu season rolls around.
“RSV continues to be the last of the major winter respiratory viruses for which we don't have a vaccine, but as these two articles in the New England Journal of Medicine indicate, we're getting close,” said Dr. William Schaffner. He is medical director of the National Foundation for Infectious Diseases, in Bethesda, Md.
The companies — GlaxoSmithKline (GSK) and Janssen — both have RSV vaccine candidates that can prevent severe illness in seniors, results show.
The GSK vaccine provides 94% protection against severe lower respiratory tract RSV, and about 83% protection against lower respiratory tract infections overall, said Dr. Leonard Friedland, vice president and director of scientific affairs and public health for GSK U.S. Vaccines.
“We're very, very pleased and excited because this is the first time that an RSV vaccine has made it through phase 3 and has published data in a peer-reviewed journal,” Friedland said.
The Janssen vaccine also provided good protection in a phase 2b proof-of-concept trial, preventing severe lower respiratory tract infection in up to 80% of patients, the results showed.
Both vaccines target the virus' F protein, which allows it to attach to human cells in a way similar to COVID's spike protein.
Earlier attempts to create an RSV vaccine in the 1960s failed. That earlier vaccine caused a phenomenon called antibody-dependent enhancement, where the antibodies produced by a vaccine actually make a virus more virulent and harmful, and two children died in the clinical trial.
In the early 2010s, U.S. National Institute of Health researchers figured out that the F protein changes shape when it binds with a human cell, and that vaccines need to target its pre-infection shape to create a protective immune response, Friedland said.
RSV is typically thought of as a children's virus that usually causes sniffles and sneezes, with occasional cases of bronchiolitis, Schaffner said.
“However, over the last 15-plus years, data have clearly indicated that RSV always was and currently is also a serious cause of upper respiratory disease and lower respiratory disease in older adults,” Schaffner said.
Every year, between 3% and 7% of people aged 65 and older are infected with RSV, Friedland said.
“That's a really high number. That's many millions of cases a year,” Friedland said. “And it's been estimated that something like 177,000 adults over 65 are hospitalized every year in the United States” due to RSV.
Seniors with a severe RSV infection typically spend three to six days in the hospital, and between 10% and 30% wind up in the intensive care unit, Friedland said. About 4% to 8% of those hospitalized die, about 14,000 deaths a year.
Worse, there's no treatment for RSV. There's Tamiflu for flu patients and Paxlovid to treat COVID-19, but no similar antiviral for RSV, Friedland said.
“So there's no way to treat it other than symptomatically with oxygen and observation, and hope that you don't get worse,” he added.
GSK tested its vaccine candidate in nearly 25,000 people aged 60 or older, with half getting one dose of vaccine and the other half getting a placebo.
The vaccine proved equally effective against both types of RSV, A and B, according to the report.
GSK's vaccine did cause some side effects in about one-third of patients. Fatigue, headache and muscle aches were the most common, but these were temporary.
The Janssen vaccine was tested in nearly 5,800 people for the phase 2b trial, which showed that it can produce an immune response sufficient to protect against severe RSV.
The U.S. Food and Drug Administration has granted a priority review of the GSK vaccine's application, Friedland said, and is expected to rule on it in May. The U.S. Centers for Disease Control and Prevention's advisory group on vaccines is to evaluate it over the summer.
“That would bring us to having a product available before the start of the '23 season in late summer or early fall,” Friedland said, adding that federal approval would prompt Medicaid and private insurers to cover the cost of vaccination.
The FDA also is reviewing an RSV vaccine candidate from Pfizer, which the company says can reduce the risk of severe illness in seniors by 86%.
Pfizer also has applied to have the vaccine approved for pregnant women, to protect infants. Clinical trials have shown that the shot is 82% effective against severe illness in babies through the first three months of life, and 69% effective through six months, the company says.
The vaccines all “look pretty good,” Schaffner said.
“We cannot expect perfection from respiratory viral vaccines," he noted. "These are not going to be vaccines that can prevent these diseases completely the way we do for many pediatric infections such as polio and measles.”
Vaccines for influenza, COVID-19 and, soon, RSV are designed to prevent severe disease, Schaffner said, “particularly lower respiratory tract disease, preventing pneumonia, preventing hospitalization and intensive care unit admission, and death and dying.”
To best treat RSV, doctors also need tests and treatments aimed at the virus, as there are for flu and COVID-19, he explained.
“In addition to the vaccines, I hope that we develop better testing that is quick, accurate and inexpensive, so that we get a better appreciation of the burden of disease in every doctor's office who cares for adults,” Schaffner said.
Findings from the new clinical trials were published Feb. 16.
The U.S. Centers for Disease Control and Prevention has more about RSV.
SOURCES: William Schaffner, MD, medical director, National Foundation for Infectious Diseases, Bethesda, Md.; Leonard Friedland, MD, vice president and director of scientific affairs and public health for GSK U.S. Vaccines, Philadelphia; New England Journal of Medicine, Feb. 15, 2023