IDWeek preview – GSK beats Pfizer

GSK had already described the efficacy of its adult RSV vaccine candidate RSVPreF3 OA as “exceptional”, and the headline numbers from an IDWeek abstract have lived up to this billing, with an impressive 83% efficacy. This looks better than Pfizer’s RSVpreF, although cross-trial comparisons are tricky, as usual. It is unclear how GSK defined lower-respiratory tract disease to calculate vaccine efficacy; for severe disease the company looked for two or more symptoms, in line with Pfizer’s definition for standard vaccine efficacy. But, if anything, this paints GSK’s candidate in an even better light. The available data also seem to contradict Pfizer’s claims that including both RSV-A and B antigens could improve efficacy: GSK’s asset only contains the RSV-A antigen, but still looked good against RSV-B. Presentation of full results on both vaccines is set for October 20. One thing to keep an eye on will be the agents’ tolerability profiles; the GSK project is adjuvanted, while Pfizer’s is not. With both jabs looking approvable, the focus will shift towards commercial execution. And more competition could be coming, with Johnson & Johnson and Moderna also set to release pivotal data with their adult candidates this winter, followed by Bavarian Nordic in mid-2023.

Duelling RSV vaccines in ≥60 year olds
  GSK Pfizer
Candidate vaccine RSVPreF3 OA (GSK3844766A) RSVpreF (PF-06928316)
Pivotal study Aresvi 006 Renoir
Vaccine efficacy 82.6%* 66.7%**
Vaccine efficacy in severe disease 94.1%** 85.7%^
Efficacy against RSV-A 84.6% ?
Efficacy against RSV-B 80.9% ?
Efficacy by age
   60-69 81.0% ?
   70-79 93.8% ?
   ≥80 33.8% ?
*Definition unclear; **≥2 symptoms; ^≥3 symptoms. Source: Company releases.

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