Moderna RSV Vaccine Protects Older Adults Against Disease, Early Data Finds

An mRNA vaccine from Moderna can effectively prevent severe illness from respiratory syncytial virus (RSV) in adults 60 years and older, the company reported this week.

Several companies have reported success from experimental RSV vaccines in recent months. Moderna’s version is 83.7% effective at protecting against RSV-associated lower respiratory tract disease with two or more symptoms.

Moderna shared some of the findings via a press release. The company said it will submit the full data set for peer review and share the results at an upcoming infectious disease medical conference. It plans to submit for regulatory approval in the first half of 2023.

Drugmakers are finalizing their vaccines as the United States is coming off a particularly challenging RSV season. November saw the highest rate of RSV-associated hospitalizations in five years—nearly five times as high as the year before.

The Moderna vaccine is now adding to an already crowded field of RSV vaccine candidates. Three companies have reported phase 3 trial data on experimental RSV vaccines and several others are in the pipeline. Some vaccines, like Moderna’s version, target older adults, while others are for pregnant mothers so their baby will be born with antibodies against the virus.  

Experts say the vaccines may help prevent such drastic waves of hospitalization among vulnerable groups.

“In the very young, or pregnant mothers, or in the older population, the vaccine might have tremendous benefit in preventing serious complications,” Aaron Glatt, MD, MACP, Chairman of the Department of Medicine at Mount Sinai Nassau and spokesperson for the Infectious Diseases Society of America, told Verywell.

For most healthy adults, RSV may cause an illness that is no worse than the common cold. But for young children and older adults, the respiratory infection can lead to serious complications. RSV causes as many as 10,000 deaths each year in adults 65 years and older, not far off from the 16,000 deaths caused by flu in the 2019–2020 season.

Moderna's RSV Vaccine Shows Strong Efficacy Data

Moderna tested the RSV vaccine, called mRNA-1345, in a randomized controlled study of about 37,000 adults 60 years or older in 22 countries.

Nine vaccinated participants got sick with RSV and experienced two or more symptoms, compared to 55 people in the placebo group.

Moderna said the vaccine was “well tolerated with no safety concerns identified.” Most adverse reactions from vaccination were mild or moderate, and most reported symptoms were injection site pain, fatigue, headache, and muscle and joint pains.

Glatt said the data is “exciting.” But experts will need to see the full study results and long-term follow-up to know that the vaccine is truly safe and effective.

“The proof is in the pudding. You need to have the real, hard data to analyze,” Glatt said. “You need to know long-term that this is going to be something that will be of continuing benefit.”

Moderna’s vaccine uses mRNA technology—the same platform the company uses for its COVID-19 vaccine and bivalent booster. mRNA technology is easily adaptable, making it useful for a variety of maladies, from preventive vaccines and cancer therapies.

The RSV vaccine will be especially important for older people with underlying conditions, Glatt said. Those with lung and heart problems are at particularly high risk of complications from RSV infection.

Multiple RSV Vaccines Are in the Pipeline

The first experimental RSV vaccine was developed in the 1960s. But testing quickly halted, as people who received that vaccine in clinical trials were more likely to get sick and die of RSV than those who took the placebo.

In 2013, researchers discovered a technique to develop safer vaccines.

Numerous companies now have RSV vaccines in the research pipeline. Glatt said he is encouraged by the results that have been shared in press releases from companies with complete phase 3 trials.

Pfizer reported that its RSV vaccine is 85.7% effective at preventing severe disease in adults older than 60. GSK’s vaccine has a reported efficacy of 94.1% in the same age group. Both vaccines could receive FDA approval as early as May.

RSV sends an average of 58,000 to 80,000 kids under the age of 5 to the hospital each year, according to the CDC.

In November, Pfizer shared that its maternal vaccine is 81.8% effective at protecting against severe disease in the first three months of an infant’s life, and then nearly 70% effective through the first six months.

There is currently no antiviral treatment for RSV, and there is only one monoclonal antibody option to help prevent severe disease. Last year, drugmakers AstraZeneca and Sanofi reported success in a phase 3 trial of a new monoclonal antibody.  

While several vaccines are expected to hit the market later this year, the RSV season usually ends around spring.

“There’s no rush to bring them to market now when we’re almost getting over the RSV season,” Glatt said. “Certainly having this available for next year would be critical.”