The RSV vaccine market collapsed, and the US Centers for Disease Control and Prevention (CDC) narrowed the scope of its vaccination recommendations, affecting companies such as GlaxoSmithKline (GSK.US) and Pfizer (PFE.US).

After a CDC expert panel last month narrowed its recommendation for RSV immunisation, healthcare analytics firm Airfinity this week cut its market forecast for the US elderly RSV vaccine by 64%,

to $1.7bn from an earlier estimate of $4.7bn, reflecting revised guidance that it said would reduce the estimated eligible population by 44% to 46mn, from 83mn.

The US RSV vaccine market includes three companies. In May, the FDA approved Moderna's (MRNA.US) RSV vaccine (mRESVIA) for use in preventing lower respiratory disease caused by the virus in people aged 60 and over.

In 2022, GlaxoSmithKline (GSK.US) and Merck (MRK.US) became the first to receive FDA approval for RSV vaccines, with the agency approving their more traditional vaccines Arexvy and Abrysvo for the same indication.

The ACIP also delayed its expected recommendation for high-risk adults aged 50-59, and the FDA expanded Arexvy's label in June.

The delayed decision may have had a $300m impact on GlaxoSmithKline, Airfinity said, with the impact potentially even greater as it used a $20m-100m priority review voucher to speed up its brand expansion.

Airfinity's RSV head Isabella Huettner said: "The ACIP recommendation may impede revenue growth in the US market unless there is new data to support the benefits of a booster." She added that the three market payers would benefit from global roll-out.

This winter, the UK, Canada and major European countries will launch their first RSV immunisation programmes, Huettner added. "Despite this, the trend seems to be towards a single lifetime vaccine for those aged 75 and over, as the UK recently confirmed."