Sanofi and GSK have announced positive Phase 3 clinical trial results for their new COVID-19 vaccine, Vidprevtyn. The protein subunit vaccine demonstrated strong protection against severe COVID-19, including hospitalizations, offering a potentially valuable addition to the global vaccine arsenal. The companies plan to seek authorization for Vidprevtyn in the US and Europe.
Promising Efficacy Data
The Phase 3 trials, which enrolled over 10,000 adults across the US, Asia, Africa, and Latin America, evaluated a two-dose regimen of Vidprevtyn administered three weeks apart. The results indicated:
- 58% efficacy against symptomatic COVID-19
- 75% efficacy against moderate or severe COVID-19
- 100% efficacy against severe COVID-19 disease, including hospitalizations
Thomas Triomphe, an executive vice president at Sanofi, noted the significance of these findings, stating, "We’re very pleased with these data. No other global Phase 3 efficacy study has been undertaken during this period with so many variants of concern, including Omicron, and these efficacy data are similar to recent clinical data from authorized vaccines."
Performance as a Booster
In addition to its performance as a primary vaccine, Vidprevtyn showed promise as a heterologous booster. When administered to individuals previously vaccinated with Pfizer, Moderna, or adenovirus-vector vaccines (such as Johnson & Johnson and AstraZeneca), Vidprevtyn boosted neutralizing antibodies by 18- to 30-fold. The manufacturers reported no identified safety concerns in the trials.
Vaccine Technology and Availability
Vidprevtyn is a protein subunit vaccine, a more traditional vaccine technology compared to mRNA or adenovirus vector vaccines. This type of vaccine uses harmless protein fragments to stimulate an immune response. A key advantage is that it can be stored at refrigerator temperatures, facilitating easier distribution in regions with limited access to ultracold storage. Sanofi has already produced and released 100 million doses and plans to supply up to 400 million more.
The development of Vidprevtyn was supported by $2.1 billion in funding from Operation Warp Speed. Initial formulations of the vaccine did not elicit a sufficient immune response in older adults, leading to reformulation and further testing. The current Phase 3 results reflect real-world performance against several variants, including Delta and Omicron.
