Moderna’s RSV Vaccine for Adults Is in the Works, and the Results Are Promising

Moderna shared exciting news this week: The biotechnology company has an experimental respiratory syncytial virus (RSV) vaccine in the works, and its efficacy looks promising so far. According to a press release, Moderna’s RSV vaccine was 83.7% effective in preventing at least two symptoms associated with RSV in older adults (age 60 and up) in a phase-three clinical trial. The randomized, double-blind, placebo-controlled study included about 37,000 older adults in 22 countries, including the United States.

The news comes months after Pfizer announced the promising results of its experimental RSV vaccine in a late-stage clinical trial, and on the cusp of a nasty cold and flu season that was dominated by a spike in RSV infections late last year; many pediatric units across the country reported feeling overwhelmed with sick children. 

RSV is common in childhood; the virus—which typically causes cold- or flu-like symptoms with mild illness—infects most kids by the age of two, according to the Centers for Disease Control and Prevention (CDC). You’ve probably heard a lot about RSV’s potential to make young kids and infants critically ill, but the virus can also lead to serious complications in older adults. Up to 120,000 older Americans are hospitalized with RSV each year, per the CDC, and up to 10,000 of them die from the infection. Amesh A. Adalja, MD, infectious disease expert and senior scholar at the Johns Hopkins Center for Health Security, tells SELF that RSV’s possible impact on older people is “comparable” to the flu (think: trouble breathing, pneumonia, or bronchiolitis), so a vaccine that could help reduce the risk of complications would be a “major benefit.”

That’s why the preliminary results of Moderna’s phase-three trial are “really quite encouraging,” Thomas Russo, MD, chief of infectious diseases at the University at Buffalo in New York, tells SELF. There are several RSV vaccines in development, but the US Food and Drug Administration (FDA) hasn’t approved one for use yet. Here’s how Moderna’s option, among others, could change that in the near future.

How does Moderna’s RSV vaccine work?

Moderna’s RSV vaccine, called mRNA-1345, takes advantage of similar mRNA technology that the company uses in its COVID-19 vaccine, Dr. Russo says. The vaccine specifically targets F glycoprotein; this protein can be found on the surface of the virus, and it’s necessary for helping the pathogen enter cells. Research has shown that, if the protein can’t enter a person’s cells, then the virus has trouble triggering the associated illness. 

The company also noted that, so far, no safety concerns have been identified, save for potential side effects that are to be expected with nearly any vaccine; injection-site pain, fatigue, headache, and muscle/joint pain or stiffness are most commonly reported.

Why is the development of an RSV vaccine needed right now?

The United States was recently hit with a massive RSV wave, which peaked in early November. “We’ve had the big ‘tripledemic’—influenza and COVID, both of which we have vaccines for, and RSV, for which we do not,” William Schaffner, MD, infectious disease specialist and professor of medicine at the Vanderbilt University School of Medicine in Nashville, tells SELF. When three major viruses collide as they have in the last few months, everyone has a higher chance of getting sick—especially those who are most vulnerable, like young children, seniors, pregnant people, and people who are immunocompromised. High case counts can stress our health care systems and make it tougher for people to get the critical care they need to recover.

While Dr. Russo says there’s a “high likelihood” that younger adults would also benefit from an RSV vaccine, pharmaceutical companies are currently focusing their efforts on older adults due to their high risk of developing complications. “Some seasons, the RSV impact is comparable to that of influenza in terms of requiring older adults to seek medical care,” Dr. Schaffner says. “Some are hospitalized and even end up dying.”

Plus, once we have a safe, effective RSV vaccine for adults, we’ll get one step closer to having a safe, effective vaccine for kids (no doubt to the relief of parents and other caregivers).

Moderna confirmed it plans to submit its data to the FDA in the first half of 2023, with the hopes of having its vaccine approved for use; Pfizer is also seeking regulatory approval for its RSV vaccine. But when will we actually see one reaching arms?  “If you’re very optimistic,” Dr. Schaffner says, “the first RSV vaccine for seniors may be coming this fall.”

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