GlaxoSmithKline (GSK) and Medicago have reported that a plant-based Covid-19 vaccine candidate, given with an adjuvant showed an overall efficacy of 71% against all SARS-CoV-2 variants in a Phase III clinical trial.

The study evaluated Medicago’s plant-based vaccine candidate for Covid-19 in combination with the pandemic adjuvant of GSK.

Commenced in March 2021, the randomised, event-driven, crossover placebo-controlled, observer-blinded Phase III segment of a Phase II/III trial analysed the efficacy and safety of the vaccine candidate versus placebo.

It enrolled more than 24,000 participants aged 18 years and above in the US, UK, Canada, Mexico, Argentina and Brazil.

The trial subjects received two intramuscular doses of the vaccine at a gap of 21 days.

For the Delta variant of the virus, findings showed that the vaccine candidate had a 75.3% efficacy against Covid-19 of any severity.

GSK noted that the trial met the primary and secondary endpoints, and the vaccine also had an 88.6% efficacy against the Gamma variant.

No significantly serious side effects were observed in the trial with mild to moderate and temporary reactogenicity noted.

The shot was found to be well-tolerated with the safety profile in the Phase III trial in line with that reported in Phase II.

Based on the latest data, Medicago intends to obtain approval from Health Canada as part of the rolling submission.

In April, the Canadian regulatory authority accepted for review the initial portion of the rolling submission made by Medicago for its vaccine candidate.

GSK global Covid-19 adjuvanted vaccines lead and chief global health officer Thomas Breuer said: “These are encouraging results given data were obtained in an environment with no ancestral virus circulating.

“The combination of GSK’s established pandemic adjuvant with Medicago’s plant-based vaccine technology has significant potential to be an effective, refrigerator-stable option to help protect people against SARS-CoV-2.”

GSK collaborated with Medicago to develop, evaluate and produce a plant-based adjuvanted Covid-19 shot, in July 2020.