After decades of setbacks, the respiratory syncytial virus (RSV) vaccine field has bounced back with positive Phase III trial results in older adults. There are currently five players in the race, with vaccines in Phase III of development from GlaxoSmithKline (GSK), Pfizer, Johnson & Johnson, Moderna and Bavarian Nordic. However, recent data from GSK’s sub-unit vaccine, GSK-3844766A, have pushed the candidate to the top, with the highest efficacy demonstrated in a pivotal trial to date.

GSK’s Phase III pivotal trial included roughly 25,000 adults aged 60 years and older across 17 countries. The most recent results were announced on 13 October and showed an impressive 94.1% efficacy against severe RSV disease, along with an overall vaccine efficacy of 82.6%. The results also demonstrated consistent efficacy against both RSV subtypes, RSV-A and RSV-B, as well as a favourable safety profile. More specifically, the data suggest an efficacy rate of 93.8% in adults aged 70-79 years and 94.6% in adults with comorbidities such as cardiovascular conditions, which represent the patient populations at highest risk of death if contracting the virus.

GSK’s RSV older adult vaccine candidate contains a recombinant subunit prefusion RSV F glycoprotein antigen combined with proprietary AS01E adjuvant. There are currently no approved RSV vaccines in any population. The Japanese Ministry of Health, Labour and Welfare (MHLW) has accepted GSK’s New Drug Application (NDA) for review in adults aged 60 years and older to prevent lower respiratory tract diseases caused by RSV. Further regulatory updates from the US and EU are expected by the end of the year. Those at high risk of severe illness from RSV include older adults, adults with chronic lung or heart disease, and adults with weakened immune systems.

If approved, GSK’s GSK-3844766A will be the first vaccine to reach the market for the prevention of RSV in older adults, gaining a significant first-mover advantage. More importantly, this potential approval may dramatically reduce the global burden of RSV in older adults during the current Covid-19 pandemic.