A new plant-based vaccine, Covid-19, is nearly 70% effective against symptomatic disease caused by five variants of the coronavirus, according to the results of a human clinical trial of the preventive.
The vaccine, developed by researchers at Canadian biotechnology company Medicago, contains coronavirus-like particles (CoVLP) produced in plants that are combined with an adjuvant (ASO3) that helps vaccines work better.
The phase 3 study of the vaccine was conducted in 85 centers involving 24,141 adults who were randomized to receive two intramuscular injections of either CoVLP + AS03 or placebo with a 21-day interval.
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The researchers confirmed Covid-19 by polymerase chain reaction (PCR) test in 165 participants.
The study, published Thursday in the New England Journal of Medicine (NEJM), showed that the vaccine was 69.5% effective against each symptomatic Covid-19 caused by five variants.
In a statistical analysis, the effectiveness of the vaccine was 78.8 and 74.0%, respectively, against moderate to severe disease and among those who were seronegative in the beginning, the researchers said.
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“The CoVLP + AS03 vaccine is effective in preventing Covid-19 caused by a range of variants, with efficacy ranging from 69.5% for symptomatic infection to 78.8% for moderate to severe disease,” the study authors said.
There were no severe cases of Covid-19 in the vaccine group, the researchers said.
The average viral load for breakthrough cases is more than 100 times lower in the vaccine group than in the placebo group, they said.
Adverse events were predominantly mild or moderate and transient and occurred more frequently in the vaccine group than in the placebo group, according to the researchers.
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Local adverse events occurred in 92.3 and 45.5% of the vaccine and placebo groups, respectively, and systemic adverse events occurred in 87.3 and 65.0%, respectively, they said.
“The potential effect of this plant technology in the current pandemic will be strongly influenced by the evolution of the pandemic itself,” the authors note. “However, the availability and further development of this platform could have important implications for pandemic preparedness,” they added.
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The researchers noted that the effectiveness of the vaccine among adults aged 65 and over could not be determined due to the limited number of participants in this age group.
However, previous evidence suggests that the CoVLP + AS03 vaccine elicits similar immune responses in both young and older people, they said.
Several authors of the study revealed financial ties to Medicago, which funded the study and is the maker of the CoVLP + AS03 vaccine.
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