This Phase 2/3 study is a multi-portion design to confirm that the chosen formulation and dosing regimen of CoVLP has an acceptable immunogenicity and safety profile.

The Phase 2 portion of the trial was a randomized, observer-blind, placebo-controlled study to evaluate the safety and immunogenicity of the adjuvanted recombinant COVID-19 plant-derived vaccine candidate in subjects aged 18 and above. It was conducted in multiples sites in Canada and the United States in a population composed of healthy adults (18-64y), elderly adults (over 65y) and adults with comorbidities. Each age group enrolled up to 306 subjects randomized 5:1 to receive the adjuvanted CoVLP vaccine candidate: placebo and with 2:1 stratification in older adults (65-74 and ≥75). All subjects will be followed for a period of 12 months after the last vaccination for the assessment of safety and durability of the immune responses to the vaccine candidate which will be the final analysis.

The Phase 3 portion is an event-driven, randomized, observer-blinded, placebo-controlled design that will evaluate the efficacy and safety of the CoVLP formulation compared to placebo.

Subjects will be followed for safety and immunogenicity for a period of 12 months after the last vaccination.

Results

On May 4, 2022, The New England Journal of Medicine published the results of this trial. 

A total of 24,141 volunteers participated in the trial. Vaccine efficacy was 69.5% (95% confidence interval [CI], 56.7 to 78.8) against any symptomatic Covid-19 caused by five variants that were identified by sequencing. In a post hoc analysis, vaccine efficacy was 78.8% (95% CI, 55.8 to 90.8) against moderate-to-severe disease and 74.0% (95% CI, 62.1 to 82.5) among the participants who were seronegative at baseline. No severe cases of Covid-19 occurred in the vaccine group, in which the median viral load for breakthrough cases was lower than that in the placebo group by a factor of more than 100. 

Conclusions

The CoVLP+AS03 vaccine was effective in preventing Covid-19 caused by a spectrum of variants, with efficacy ranging from 69.5% against symptomatic infection to 78.8% against moderate-to-severe disease.

Interim Results

Medicago's vaccine candidate with GSK's pandemic adjuvant exhibited an acceptable safety profile and adverse events (AE) were primarily mild or moderate and of transient duration. AEs in Older Adults were more limited than those observed in the Adult population. 

Medicago's vaccine candidate with GSK's pandemic adjuvant induced a significant humoral immune response of similar strength in both age cohorts after two doses.  The vaccine candidate induced a greater humoral response in Adults than Older Adults after a single dose but after the second dose both age cohorts responded with NAb titers that were about 10 times higher than those in a panel of sera from patients recovering from COVID-19.