French healthcare company Sanofi S.A. (Euronext Paris:SAN) (Nasdaq:SNY) announced on Saturday that its protein-based COVID-19 vaccine, Nuvaxovid (NVX-CoV2705), showed statistically significant lower systemic reactogenicity compared to mNEXSPIKE (mRNA-1283), Moderna's (NASDAQ:MRNA) mRNA-based vaccine, in a head-to-head phase 4 study.

The randomised, double-blind trial enrolled 1,000 adults in the United States and was presented at the ESCMID Global Congress in Munich. The study met its primary endpoint, with 91.6% of mNEXSPIKE recipients experiencing at least one systemic reaction within seven days compared to 83.6% of Nuvaxovid recipients.

Across secondary measures, Nuvaxovid demonstrated reduced severity and duration of side effects. Moderate-to-severe systemic symptoms were reported in 43.1% of Nuvaxovid recipients compared to 61.3% for mNEXSPIKE, while moderate-to-severe local reactions occurred in 38.7% versus 58.7%, respectively. Severe systemic symptoms were more than 50% less frequent with Nuvaxovid, and severe local reactions were over 75% less frequent. Patient-reported outcomes indicated less disruption to daily activities and higher willingness to receive the same vaccine again.

The findings address ongoing challenges in COVID-19 vaccination uptake, where concerns over side effects remain a key barrier despite continued global hospitalisations and seasonal healthcare strain.