fb-pixel Skip to main content

Moderna says its RSV vaccine protects older adults

The experimental shot reduced the risk of developing virus symptoms by nearly 84 percent in a study of 37,000 adults age 60 and older.

Moderna's RSV vaccine used the same RNA technology and lipid nanoparticle chemistry as its COVID-19 vaccine.Craig F. Walker/Globe Staff/file

An experimental vaccine made by Moderna was nearly 84 percent effective in preventing symptoms of RSV infections in a large study of older adults, the Cambridge company said Tuesday, raising hopes that the seemingly indomitable virus may at last yield to scientists’ efforts to subdue it.

There are no approved shots for RSV, which stands for respiratory syncytial virus, so an approved vaccine would be a major advancement. The disease, which has been around for decades, commonly infects infants and the elderly and has overwhelmed hospitals this winter. Experts say that the Moderna study, plus advanced studies of two competing experimental vaccines made by Merck and Pfizer, could eventually lead to a dramatic reduction in such hospitalizations.


“It is really encouraging to see that kind of efficacy,” said Dr. Kristin Moffit, an infectious disease physician at Boston Children’s Hospital. “It could have really unbelievable implications for older adults in terms of reducing deaths.”

Between 60,000 and 120,000 older Americans are hospitalized with RSV and between 6,000 and 10,000 of them die each year, according to one estimate from the Centers for Disease Control and Prevention.

The RSV shots were made with the same messenger RNA technology and lipid nanoparticle chemistry used in Moderna’s COVID-19 vaccine. Although the company has dozens of drugs and vaccines in development, its RSV vaccine is only the second to reach and pass an advanced study. It provides important validation for biotech investors that Moderna can become more than just a COVID vaccine company.

“It’s really wonderful and reassuring to be able to build on the success of the SARS-CoV-2 vaccine,” Jacqueline Miller, Moderna senior vice president of infectious diseases said in an interview. “The most important piece is that we’re able to use the technology for more than one thing.”

Moderna said that it plans to submit the RSV vaccine to federal regulators in the first half of the year. But Miller wouldn’t say whether the vaccine could be ready for public use in time for the next RSV season, or how long it will take to fully study the vaccine in young children, where the need is the greatest.


Miller said she was “incredibly pleased” when she first saw the results of the company’s international study of 37,000 adults age 60 or older. People who received the vaccine were 83.7 percent less likely to develop two or more symptoms of lower respiratory disease than those who got a placebo shot. That boils down to 9 cases of RSV among vaccinated individuals and 55 cases in the placebo group.

“It is really exciting, because it has been a busy season between COVID, RSV, and influenza,” said Dr. James Mojica, clinical director of pulmonary medicine at Massachusetts General Hospital. “We have a large adult population that is vulnerable, and we never expect a vaccine to be perfect, but if it can lower the burden of disease, that is still a win.”

This 1981 photo provided by the Centers for Disease Control and Prevention (CDC) shows an electron micrograph of Respiratory Syncytial Virus, also known as RSV. Associated Press

“These data are encouraging, and represent the second demonstration of positive phase 3 trial results from our mRNA infectious disease vaccine platform after, Spikevax, our COVID-19 vaccine. We look forward to publishing the full data set and sharing the results at an upcoming infectious disease medical conference,” Moderna chief executive Stéphane Bancel said in a press statement.

“We certainly need to see the details and whether there is any evidence for reducing progression to severe disease,” said Dr. Daniel R. Kuritzkes, chief of the division of infectious diseases at Brigham and Women’s Hospital.


Moderna plans to continue monitoring participants to see how good the vaccine is at preventing severe disease and hospitalizations, Miller said. The company is also testing the vaccine in four earlier-stage studies, including one in children.

Early attempts to make an RSV vaccine in the 1960s unpredictably caused children to develop more severe disease, and caused two to die. Scientists later identified a misshapen RSV viral protein included in the shots as the likely culprit for that tragedy. Newer designs, including the one that Moderna uses, lock the protein into the correct shape, which is expected to improve its safety and effectiveness.

Due to the early tragedy in the field, “there’s a lot of caution in terms of how vaccination proceeds and studies proceed in the youngest kids,” Miller said. But the positive result from the adult study “really goes a long way towards making me more comfortable” with the company’s studies in children, she added.

Moderna’s other studies are assessing different combinations of its RSV vaccine together with its commercial COVID vaccine and experimental vaccines for influenza, and human metapneumovirus. The company believes that these could be more attractive to consumers, and command higher prices, because of the convenience of combining multiple vaccines into one shot.

Several other firms have their own RSV vaccine programs, including small biotech companies and two large pharmaceutical giants, GSK and Pfizer, which are both ahead of Moderna.


In August, Pfizer said its similarly sized study found its vaccine to be 66.7 percent efficacious at preventing two or more RSV symptoms, and 85.7 percent efficacious at preventing three or more symptoms in a large study of adults 60 and older. In October, GSK said its vaccine was 82.6 percent efficacious in adults 60 and older, and 94.1 percent efficacious in preventing severe disease in adults ages 70 to 79.

And in November, a second Pfizer study found that vaccinating pregnant women reduced severe RSV disease in newborn infants by 81.8 percent in the first 90 days, and by 69.4 percent through their first six months.

“That was very interesting and a really meaningful outcome,” Moffitt said. “RSV brought many children’s hospitals to a critical surge that we hadn’t seen in ages. It was like the COVID wave that adult hospitals were feeling early in the pandemic. There’s a huge need for a childhood RSV vaccine.”

Ryan Cross can be reached at ryan.cross@globe.com. Follow him on Twitter @RLCscienceboss.