Medicago, GSK Announce Positive Results for Plant-Based COVID-19 Vaccine


Primary and secondary endpoints for which data are available were met in a trial dominated by variants.

Medicago and GlaxoSmithKline plc (GSK) announced positive efficacy and safety results for Medicago’s plant-based COVID-19 vaccine candidate that uses GSK’s booster.

Vaccine efficacy was demonstrated in an environment dominated by SARS-CoV-2 variants, unlike most published phase 3 efficacy trials for licensed COVID-19 vaccines. Others were conducted when only the ancestral virus was circulating, which makes direct comparisons nearly impossible, the companies said in a joint statement.

“These are encouraging results given data were obtained in an environment with no ancestral virus circulating. The global COVID-19 pandemic is continuing to show new facets with the current dominance of the Delta variant, upcoming Omicron, and other variants likely to follow,” Thomas Breuer, global COVID-19 adjuvanted vaccines lead and chief global health officer at GSK, said in the statement.

“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,” he said.

The overall vaccine efficacy rate against all variants of SARS-CoV-2 was about 71%. The corresponding number for individuals with an initial seronegative status indicating no previous exposure to COVID-19 was 75.6%

The vaccine candidate demonstrated efficacy of 75.3% against COVID-19 of any severity for the Delta variant and was 88.6% effective against the Gamma variant.A small number of severe cases occurred in the study, but none occurred in the vaccinated group. No cases of the Alpha, Lambda, and Mu variants were observed in the vaccinated group, but 12 cases were seen in the placebo group.

The Omicron variant was not circulating during this study.

“The results of our clinical trials show the power of plant-based vaccine manufacturing technology. If approved, we will be contributing to the world’s fight against the COVID-19 pandemic with the world’s first plant-based vaccine for use in humans,” Takashi Nagao, CEO and president of Medicago, said in the statement.

The phase 3 portion of the trial began in March 2021 and was an event-driven, randomized, observer-blinded, crossover placebo-controlled design that evaluated the efficacy and safety of the vaccine candidate formulation compared with a placebo in more than 24,000 individuals in Argentina, Brazil, Canada, Mexico, the United Kingdom, and the United States.There were no related serious adverse events reported in the study. The frequency of a mild fever was less than 10%, even after the second dose.

Reactogenicity was generally mild to moderate and transient, with symptoms lasting an average of just 1 to 3 days.

The phase 3 results confirm the safety profile, and it remains consistent with phase 2 results.

The phase 2/3 study has a multi-portion design to confirm that the chosen formulation and dosing regimens of the vaccine candidate has an acceptable vaccine profile in healthy individuals aged 18 to 64 years, as well as those aged 65 years or older and individuals with comorbidities.The phase 2 portion of the study was used to evaluate the safety and immunogenicity of the adjuvanted recombinant vaccine for individuals aged 18 years and older.

The vaccine candidate is not yet approved by any regulatory authorities.

Medicago, a Canadian company that has been developing plant-based technology for the past 20 years, will seek regulatory approval from Health Canada as part of its rolling submission. The company has also begun the filing process with the FDA and the Medicines and Healthcare products Regulatory Agency in the United Kingdom. In addition, Medicago is also in preliminary discussions with the World Health Organization.


Medicago and GSK announce positive phase 3 efficacy and safety results for adjuvanted plant-based COVID-19 vaccine candidate. Medicago and GlaxoSmithKline. News release. December 7, 2021. Accessed December 8, 2021.

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