GSK plc GSK announced positive topline results from a phase III study evaluating the co-administration of its two marketed vaccines — RSV vaccine Arexvy and shingles vaccine Shingrix — in older adults (aged 50 years and older).

The study achieved its primary endpoint of non-inferior immune response — study participants who received the co-administered shot generated immune responses that were similar to those generated in participants who received each vaccine separately. Study participants who received the vaccine separately took Shingrix first followed by Arexvy at day 31.

The safety profile of the co-administered vaccine was also well-tolerated by study participants.

GSK plans to use the data from this late-stage study to support its regulatory submissions in the United States and Europe seeking approval for the co-administration of Arexvy and Shingrix shots.

GSK Stock Performance

The stock has increased 14.5% year to date compared with the industry’s 0.5% growth.

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GSK’s Vaccine Sales Slowing Down

GSK boasts a broad vaccine portfolio that targets infectious diseases like meningitis, shingles, flu, polio and many more. GSK has more than 20 marketed vaccines in its portfolio. Both Arexvy and Shingrix are key drivers of revenues for GSK’s vaccine segment. Since this year’s onset, vaccine sales have been faltering.

GSK’s Vaccine sales declined 2% in the United States in the first half of 2024 mainly due to declining sales of Shingrix. U.S. sales of Shingrix declined 19% in the first half of 2024 due to changes in retail vaccine prioritization due to a new Medicare rule, effective this January, which changed how pharmacies process reimbursements from payers. Lower demand is driven by challenges activating harder-to-reach consumers. U.S. sales of Shingrix are expected to remain soft in the second half.

Revised recommendations for RSV vaccinations issued in June by the US Advisory Committee on Immunization Practices (ACIP) are expected to hurt sales of Arexvy. In June, the ACIP recommended the use of Arexvy for all adults aged 75 and above. However, for adults aged 60-74, the ACIP recommended the vaccine only for those who are at increased risk of severe RSV disease. The ACIP also postponed a vote for adults aged 50-59. GSK expects minimal sales of Arexvy in the 50-59 group in 2024 and also sales in the 60-74 group will be affected by ACIP’s recommendation.

It was due to these factors that, on the Q2 conference call, management lowered its vaccine sales growth expectations from a range of high single-digit to low double-digit percentage to a range of low to mid-single-digit percentage at CER in 2024.