In a recent development, a panel of outside experts advising the U.S. Centers for Disease Control and Prevention (CDC) has narrowed its recommendation for the use of respiratory syncytial virus (RSV) vaccines in older adults. The CDC's Advisory Committee on Immunization Practices voted to recommend RSV shots for adults aged 75 and older, as well as those aged 60 to 74 who have an increased risk of severe RSV due to medical conditions.

Last year, pharmaceutical companies GSK and Pfizer competed in the RSV vaccine market for all adults aged 60 and over. However, Moderna recently gained approval from the U.S. Food and Drug Administration (FDA) for its RSV shot, mRESVIA, for the same age group. GSK's vaccine was also granted FDA approval earlier this month for use in adults aged 50 to 59 at increased risk. However, the CDC committee postponed endorsing its use in this age group, citing a greater level of uncertainty regarding the balance of risk and benefits.

The committee's decision has led to a decline in the shares of all three vaccine makers. GSK's U.S.-listed ADRs are down approximately 4%, Pfizer shares have decreased by around 2.3%, and Moderna has seen a significant plunge of about 10%.

RSV, which commonly presents as cold-like symptoms, is a major cause of pneumonia in both toddlers and older adults, causing thousands of hospitalizations and deaths each year in the United States. The combined revenue for the Pfizer and GSK RSV vaccines in their first year of availability exceeded $2.4 billion.

Analysts predict sales of $1.59 billion for GSK's RSV shot, $1.47 billion for Pfizer's vaccine, and $370 million for Moderna's mRESVIA shot this year. Moderna presented data at the meeting that showed its vaccine had a 50% efficacy rate in preventing RSV for 18 months, slightly lower than what GSK and Pfizer had previously demonstrated in their own clinical trials. Moderna has urged against making direct comparisons, as the trials were conducted differently and used different criteria for defining RSV disease.

It is important to note that adults who have already received an RSV shot are not recommended to receive another this year, as per the committee's vote. The final decision regarding the CDC's recommendations lies with the agency's director, and their guidance also plays a vital role in determining insurance coverage in the U.S., particularly for those covered by the government's Medicare program.

The committee's decision to narrow the age recommendation for RSV shots highlights the ongoing efforts to combat the impact of this virus on vulnerable populations. With the vaccine market now facing new dynamics, GSK, Pfizer, and Moderna will continue to navigate the evolving landscape and make necessary adjustments to their strategies moving forward.