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Sanofi, GSK say COVID vaccine works as booster, but delay key study results

Sanofi and GSK expected to have definitive results for their long-delayed coronavirus vaccine by now, having redesigned their shot after an initial formulation disappointed late last year.

A verdict on whether their revamped vaccine can match the effectiveness of other vaccines in preventing COVID-19 is likely coming soon, with the companies indicating the trial will continue into “early 2022.” But results will have to be particularly strong for the shot to be used in countries with ready supplies of others from Pfizer, Moderna, Johnson & Johnson and AstraZeneca.

Complicating matters further is the omicron variant, which appears likely to at least partially escape the protection provided by available vaccines. (Much of the preliminary data now available is focused on Pfizer’s vaccine, and booster doses seem to offer strengthened immunity even against omicron.)

Should Sanofi and GSK’s vaccine prove effective against COVID-19, the results released Wednesday may help position the shot as a potential booster dose, particularly in areas with less supply of other vaccines.

The small study, which enrolled a little over 500 participants, tested one dose of the companies’ protein-based vaccine four to 10 months after the volunteers had received an approved primary series of Pfizer, Moderna, J&J or AstraZeneca’s shots.

Participants were enrolled across the U.S., U.K. and France and the trial is continuing to assess other vaccine formulations targeting the beta coronavirus variant. More data could come in the first half of next year, although the companies noted that omicron was not circulating during the trial.

Instead, Sanofi and GSK are using blood samples from booster dose participants to measure how much their vaccine can help in neutralizing omicron.

But the companies’ booster dose data will mean little until results are available from the larger Phase 3 trial, which began in late May and has enrolled more than 10,000 participants across its first stage. A second phase is evaluating a tweak on the companies’ formulation to incorporate targeting of the beta variant, which shares some of the mutations found on omicron.

An independent committee monitoring the trial recommended it continue so more data could be collected, particularly in people who have not been previously infected by the coronavirus. That became a harder task in the later summer and fall, when the delta variant spurred waves of infections in many countries.

The committee identified no safety concerns, Sanofi and GSK said.