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Efficacy and Safety of a Recombinant Plant-Based Adjuvanted Covid-19 Vaccine
Karen J Hager1, Gonzalo Pérez Marc1, Philipe Gobeil1
1From Medicago, Quebec, QC (K.J.H., P.G., G.H., A.I.M., S.P., P.S., K.B., J.A., I.B., J.D., N.C., M.M.J.C., J.J.-W., N.L., S.L., A.L., A.M., E.P., J.P., A.S., L.T., J.N., M.-A.D., S.T., Y.K., B.J.W.), Dawson Clinical Research, Guelph, ON (G.W.), and Research Institute of the McGill University Health Center, Montreal (B.J.W.) - all in Canada; Hospital Militar (G.P.M.) and Fundación INFANT (F.P.P.), Buenos Aires, Clinica Mayo de Urgencias Medicas Cruz Blanca, Tucuman (C.L.), and Sanatorio Allende, Cordoba (F. Riera) - all in Argentina; the Infectious Diseases Division, Paulista School of Medicine, Federal University of São Paulo, and Azidus Brasil Pesquisa e Desenvolvimento, São Paulo (R.S.D., L.F.), Instituto de Pesquisas Clinicas L2IP, Brasilia (E.V.), and Instituto Brasil de Pequisa Clinica, Rio de Janeiro (P.G.W.) - all in Brazil; Hope Clinical, Canoga Park, CA (H.A.); Clinical and Experimental Sciences, University of Southampton and NIHR Southampton Clinical Research Facility and Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom (C.E.J.); the Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore (L.H.M.); and GlaxoSmithKline Vaccines, Wavre, Belgium (T.B., M.-A.C., M.K., F. Roman).
Background:
Coronavirus-like particles (CoVLP) that are produced in plants and display the prefusion spike glycoprotein of the original strain of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are combined with an adjuvant (Adjuvant System 03 [AS03]) to form the candidate vaccine.
Methods:
In this phase 3, multinational, randomized, placebo-controlled trial conducted at 85 centers, we assigned adults (≥18 years of age) in a 1:1 ratio to receive two intramuscular injections of the CoVLP+AS03 vaccine or placebo 21 days apart. The primary objective of the trial was to determine the efficacy of the CoVLP+AS03 vaccine in preventing symptomatic coronavirus disease 2019 (Covid-19) beginning at least 7 days after the second injection, with the analysis performed after the detection of at least 160 cases.
Results:
A total of 24,141 volunteers participated in the trial; the median age of the participants was 29 years. Covid-19 was confirmed by polymerase-chain-reaction assay in 165 participants in the intention-to-treat population; all viral samples that could be sequenced contained variants of the original strain. 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. Solicited adverse events were mostly mild or moderate and transient and were more frequent in the vaccine group than in the placebo group; local adverse events occurred in 92.3% and 45.5% of participants, respectively, and systemic adverse events in 87.3% and 65.0%. The incidence of unsolicited adverse events was similar in the two groups up to 21 days after each dose (22.7% and 20.4%) and from day 43 through day 201 (4.2% and 4.0%).
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. (Funded by Medicago; ClinicalTrials.gov number, NCT04636697.).
