Sanofi and GSK announcedthis morning their COVID-19 vaccine candidate demonstrated a strong immune response in adults in a phase 2 clinical trial.

Why it matters: Sanofi and GSK say their recombinant protein-based vaccine candidate could ultimately serve as a universal COVID-19 vaccine booster, able to boost immunity regardless of the vaccination first received.

• It could also ultimately help ease the ongoing global supply needs for vaccines.

Details: Sanofi and GSK said the vaccine triggered an antibody response in 95% to 100% of all the trial participants, ages 18 to 95, who got the vaccine.

• The companies also observed a "high immune response after a single dose in patients" who previously recovered from COVID-19, which shows the vaccine has strong booster potential.
• It's a promising development after the companies had to delay their vaccine in December to improve immune response in older adults. Still, it's also important to point out this is a phase 2 clinical trial, a relatively small study with 722 volunteers in the U.S. and Honduras.

A global Phase 3 trial with more than 35,000 participants from various countries is expected to start in the coming weeks to test the efficacy of two vaccine formulations against variants, officials said.

• In parallel, the companies also plan to conduct booster studies.
• Should the candidate prove successful in clearing Phase 3 testing and other regulatory hurdles, officials said a vaccine could be approved by the end of 2021.