An adjuvant is added to some vaccines to enhance the immune response, which creates stronger immunity against infections.
In this case, Medicago's vaccine uses virus-like particles grown in a close relative of the tobacco plant. The vaccine combines the particles with GSK's adjuvant to generate an immune response.
The two companies announced on Thursday that the vaccine candidate was entering Phase 2 and 3 clinical trials.
The trial will evaluate the vaccine's efficacy, safety and ability to provoke an immune response.
"Our Phase 1 results of the adjuvanted vaccine candidate were very encouraging and fully support further clinical evaluation," Nathalie Landry, executive vice president of scientific and medical affairs at Medicago, said Thursday.
"This is the first of several GSK Covid-19 vaccine candidate collaborations to start Phase 2/3 clinical testing and an important step forward in our contribution to the global fight against the pandemic," Thomas Breuer, chief medical officer of GSK Vaccines, said.
The Phase 2 trial will part be conducted in multiple sites in Canada and, upon allowance from the US Food and Drug Administration, in the US.
The volunteers will include healthy adults ages 18 to 64 and elderly adults over 65, according to the announcement. Each age group will include more than 300 subjects.