Moderna secures FDA nod for RSV vaccine

The U.S. Food and Drug Administration (FDA) has approved Moderna's vaccine, mResvia, for preventing respiratory syncytial virus (RSV) in adults aged 60 and over. This approval comes one year after similar vaccines from GSK and Pfizer received the green light. The Centers for Disease Control and Prevention (CDC) will meet next month to discuss usage recommendations for the new vaccine. Moderna plans to have mResvia available in time for the upcoming fall immunization season.

RSV poses a significant threat, causing severe respiratory illness in infants, the elderly, and immunocompromised individuals, potentially leading to death. The virus typically spreads during the fall and winter, much like influenza and COVID-19. According to Amesh Adalja, an assistant professor at Johns Hopkins Bloomberg School of Public Health, RSV's impact on adult health is now being recognized, and he anticipates that more vaccine options will improve vaccination rates.

Developing a safe and effective RSV vaccine has been a long-standing challenge for scientists. However, a breakthrough in 2013 paved the way for the current vaccines now entering the market. GSK's Arexvy was the first to receive U.S. approval for older adults, followed by Pfizer's Abrysvo. Pfizer later received additional approval for maternal use of Abrysvo.

The demand for RSV vaccines has been substantial. In its first year, Arexvy generated approximately $1.5 billion for GSK, significantly boosting the company's vaccine revenues. Pfizer's Abrysvo also performed well, reporting $515 million in sales for 2023. Moderna aims to compete in this growing market, especially as it faces declining sales of its popular COVID-19 vaccine.

Similar to its COVID vaccine, mResvia utilizes messenger RNA (mRNA) technology to help the body recognize the prefusion F protein of RSV. Moderna claims its vaccine offers advantages in preparation and delivery, featuring a prefilled syringe that simplifies administration compared to its competitors' more complex formulations. CEO Stéphane Bancel emphasized that this ready-to-use format could ease the burden on pharmacies.

The upcoming CDC meeting in June is crucial, as pharmacy contracts will likely be finalized following the agency's recommendations. Given RSV's seasonal nature, immunization efforts typically ramp up in late summer to early fall. This trend was evident earlier this year when sales of Arexvy and Abrysvo dropped after the peak months of October to December.

Moderna projects the RSV vaccine market will grow to between $6 billion and $8 billion annually. However, analysts like Jefferies' Michael Yee question how much market share Moderna can capture as a late entrant. Amesh Adalja pointed out that Moderna might struggle due to its delayed entry and existing skepticism toward mRNA vaccines.

Conversely, Dan Barouch, an immunologist at Harvard Medical School, is optimistic about mResvia's prospects. He believes the strong demand for RSV vaccines will benefit Moderna, and skepticism over COVID-19 vaccines will not significantly impact uptake.

Moderna anticipates around $4 billion in net sales for 2024, combining revenues from its COVID-19 and RSV vaccines, though it has not provided specific projections for mResvia. In clinical trials, mResvia demonstrated about 84% effectiveness against RSV-related illness with two or more symptoms, comparable to GSK's vaccine. Pfizer's Abrysvo appeared slightly less effective, though direct comparisons are challenging.

All three vaccines showed a decline in efficacy over time, with mResvia's effectiveness dropping to approximately 63% after 8.6 months. Safety profiles for all three vaccines were generally positive, with common side effects including fatigue, headache, and injection site pain. The CDC has noted a potential but unconfirmed link between the vaccines and Guillain-Barré syndrome, an autoimmune disorder.

While initial vaccination efforts have focused on older adults, companies are exploring broader eligibility. Moderna is testing mResvia in high-risk adults aged 18 and older, and Pfizer has conducted similar trials. GSK is awaiting regulatory approval for Arexvy for adults aged 50 to 59.