On Tuesday, the FDA approved Pfizer Inc's (PFE  ) Abrysvo (Respiratory Syncytial Virus Vaccine), the company's bivalent RSV prefusion F (RSVpreF) vaccine, to prevent lower respiratory tract disease (LRTD) caused by RSV in individuals 18 through 59 who are at high risk.

Abrysvo now offers the broadest RSV vaccine indication for adults, which previously included those 60 years and older.

Additionally, it remains the only RSV immunization approved for pregnant individuals at 32 through 36 weeks of gestation to protect infants from birth up to 6 months of age.

The FDA's decision is based on inferred efficacy from the pivotal Phase 3 MONeT study, which investigated the safety, tolerability, and immunogenicity of Abrysvo in adults at risk of RSV-associated disease due to certain chronic medical conditions.

The company intends to submit MONeT results for publication in a peer-reviewed scientific journal and for presentation at an upcoming scientific conference.

In June, the U.S. Centers for Disease Control and Prevention's (CDC) Advisory Committee on Immunization Practices (ACIP) voted to recommend the routine use of Respiratory Syncytial Virus (RSV) vaccines in all adults aged 75 and above.

ACIP postponed a vote on a recommendation for adults aged 50-59 years at increased risk for RSV-LRTD until additional data became available.

U.S. sales of RSV vaccines from GSK Plc (GSK  ) and Pfizer have declined after regulators narrowed the age group eligible for the shots and determined they would be a one-time vaccination for now.

For Pfizer and GSK, RSV vaccines are critical as they seek to build new revenue streams before facing generic competition for their top-selling drugs.

In 2023, an average of 440,000 people per week received RSV vaccines from GSK and Pfizer in September, with 65% opting for GSK's Arexvy. However, this September, the weekly average fell to 157,000.

Price Action: PFE stock is down 0.36% at $28.74 at last check Wednesday.