Study: Efficacy and Safety of a Recombinant Plant-Based Adjuvanted Covid-19 Vaccine. Image Credit: dewa hartawan/Shutterstock

Evaluation of the results of a phase 3 clinical trial of a plant-based COVID-19 vaccine

recent article in New England Journal of Medicine Provide safety and efficacy profiles for a plant-based coronavirus 2019 (COVID-19) vaccine in human participants.

Study: Efficacy and safety of a recombinant plant-based Covid-19 Adjuvanted vaccine. Image Credit: dewa hartawan / Shutterstock

The vaccine consists of plant-derived coronavirus-like particles that expose the pre-fusion-stabilized, full-length spike protein to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The vaccine shows 70% preventive efficacy against symptoms of COVID-19 caused by various viral variants.


Scientists have used a plant platform to produce a vaccine for coronavirus-like particles. Several pre-existing viral vaccines developed using a vegan platform have shown significant efficacy and immunogenicity. Expression of SARS-CoV-2 protein elevated in plant (Nicotiana pantamiana) The cells result in the production of coronavirus-like particles (100-150 nm) displaying the pre-fixed full-length spike protein. After extraction and purification from plant cells, these particles remain stable for at least 6 months at 2 to 8 °C.

The coronavirus-like particles are also fused with adjuvant system 03 (AS03), which has previously been shown to induce a strong innate immune response and increase the robustness and robustness of the adaptive immune response. In previous studies, the vaccine was found to induce a strong and durable neutralization and balanced response of T cells.

In the current Phase 3, multicenter, multinational, randomized, placebo-controlled clinical trial, scientists have tested the safety and efficacy of the vaccine.

study design

The trial was conducted on a total of 24,141 adult participants. Participants were from 85 different locations in Argentina, Brazil, Canada, Mexico, the United Kingdom, and the United States. They were randomly divided into two groups: the vaccine group and the placebo group (control group).

In the vaccine group, participants received two doses of the vaccine intramuscularly 21 days apart. Similarly, control participants received a placebo. The trial primarily aimed to determine the efficacy of the vaccine in preventing symptoms of COVID-19 at least 7 days after the second vaccination. The safety profile of the vaccine was also evaluated in the trial.

Important notes

A total of 165 laboratory-confirmed COVID-19 cases were identified in the entire study population. Whole-genome sequencing data confirmed that these cases were caused by five different types of SARS-CoV-2, including alpha, gamma, delta, mu and lambda variants.

Of all the enrolled participants, 12,074 received the vaccine and 12,067 received the placebo. A total of 11,234 participants received two doses of the vaccine and continued the trial on day 42. Similarly, a total of 9,897 participants received two doses of the placebo and continued the trial on day 42.

Because of specific reasons, some participants discontinued after day 42. Thus, the final analysis was performed on 10,554 participants in the vaccine group and 9,536 participants in the placebo group.

Vaccine efficacy

Considering all study participants regardless of their initial serostatus (SARS-CoV-2 antibody status), the vaccine’s efficacy against COVID-19 symptoms was estimated to be 69.5%.

The vaccine’s effectiveness against COVID-19 symptoms was about 68.9% in healthy adults under 65 years of age. In participants with comorbidities, the efficacy was approximately 79%.

The overall vaccine efficacy against moderate to severe COVID-19 was about 78.8%. Among the negative participants (those without detectable antibodies against SARS-CoV-2 at baseline), efficacy against moderate to severe disease was 74%.

The efficacy of a specific vaccine was estimated among participants with confirmed COVID-19. Estimates of overall vaccine efficacy against the alpha, mu and lambda variants were 100%. Against the gamma and delta variables, the efficacy estimates were 87% and 74%, respectively. Further analysis revealed that the average viral load in the vaccine group was a factor of over 100 lower than in the placebo group.

Vaccine safety

Regarding desired adversities, approximately 92% of participants in the vaccine group and 45% of participants in the placebo group reported local adverse events after the first and second vaccinations. Systemic adverse events were reported by 87% and 65% of participants in the vaccine and placebo groups, respectively.

In both groups, the most common local adversity was pain at the injection site. The most common systemic adversities were headache, muscle aches, fatigue, and general discomfort. About 2.1% and 0.1% of participants in the vaccine group and participants in the placebo group reported severe local adverse events after the second vaccination, respectively. Similarly, severe systemic adverse events were reported in 3.1% and 0.5% of participants, respectively.

Regarding undesirable adversities after the first and second vaccinations, the number of reports was slightly higher in the vaccine group than in the placebo group. No vaccination-related deaths occurred during the study period.

Study the importance

The study describes the safety and efficacy profiles of the first plant-based COVID-19 vaccine approved for human use. The vaccine is highly effective in preventing severe and symptomatic COVID-19. Furthermore, the vaccine is well tolerated in the study population.

2022-05-05 15:38:00

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