ABSTRACT
BackgroundSeveral COVID-19 vaccines are currently being deployed but supply constraints, concerns over durability of immune responses, solidifying vaccine hesitancy/resistance and vaccine efficacy in the face of emerging variants mean that new vaccines continue to be needed to fight the ongoing pandemic. The vaccine described here is an enveloped, coronavirus-like particle produced in plants (CoVLP) that displays the prefusion-stabilized spike (S) glycoprotein of SARS-CoV-2 (ancestral Wuhan strain) and is adjuvanted with AS03 (CoVLP+AS03). MethodsThis Phase 3 randomized, observer-blind, placebo-controlled trial was conducted at 85 centers in Argentina, Brazil, Canada, Mexico, the UK, and the USA. Adults [≥]18 years of age including those at high risk for COVID-19 complications were randomly assigned 1:1 to receive two intramuscular injections of CoVLP (3.75 g) adjuvanted with AS03 or placebo, 21 days apart. The primary efficacy endpoint was prevention of symptomatic ([≥] 1 symptom), PCR-confirmed SARS-CoV-2 infection with onset at least 7 days after the second injection and was triggered by the identification of [≥]160 virologically-confirmed cases. Tolerability and safety of CoVLP+AS03 were also determined. ResultsA total of 24,141 volunteers were randomly assigned 1:1 to receive vaccine or placebo (N= 12,074 and 12,067, respectively: median age 29, range 18 to 86 years). Overall, 83% received both doses. 14.8% were SARS-CoV-2 seropositive at baseline. Symptomatic SARS-CoV-2 infection was confirmed in 165 study participants in the intention to treat (ITT) set and 157 in the per-protocol population (PP) set. Of the 157 in the PP set, 118 COVID-19 cases were in the placebo group and 39 COVID-19 cases were in the CoVLP+AS03 group for an overall vaccine efficacy (VE) of 71.0% (95% confidence interval (CI) 58.6, 80.0). Moderate-to-severe COVID-19 occurred in 8 and 32 participants in the CoVLP+AS03 and placebo groups, respectively: VE 78.1% (95% CI: 53.9, 90.5) in the PP set overall and 84.5% (95% CI: 62.0, 94.7) in those seronegative at recruitment. To date, 100% of the sequenced strains (122/165 cases: 73.39%) were variants, dominated by Delta (45.9%) and Gamma (43.4%) strains. Vaccine efficacy by variant was 75.3% (95% CI 52.8, 87.9) against Delta and 88.6% (95% CI 74.6, 95.6) against Gamma. Cross-protection was also observed against Alpha, Lambda and Mu variants; although fewer cases were identified, all were in the placebo group. At diagnosis, viral loads in the CoVLP+AS03 breakthrough cases were >100-fold lower than in the placebo cases. Reactogenicity data for solicited adverse events (AEs) was analysed for a subset (N=4,136 in vaccine arm and N=3,683 for placebo) of participants. Reactogenicity was mostly mild to moderate, and transient, and occurred more frequently in the CoVLP+AS03 group. The safety analysis set used for unsolicited AE assessment comprised 24,076 participants who received at least one study injection: 12,036 received CoVLP+AS03 and 12,040 received placebo. All serious adverse events were assessed as unrelated, except two events reported in the same subject in the placebo group. No significant imbalance or safety concern was noted in medically attended AEs (MAAEs), adverse event of special interest (AESIs), AEs leading to withdrawal, deaths, or adverse events potentially associated with currently authorized vaccines. ConclusionsThe CoVLP+AS03 vaccine candidate conferred an efficacy of 71.0% in preventing symptomatic SARS-CoV-2 infection caused by a spectrum of variants. Vaccine efficacy of 78.1% was observed against moderate and severe disease, while variant-specific efficacy ranged from 75.3% to 100%. Markedly lower viral loads in the CoVLP+AS03 group at the time of diagnosis suggests a significant virologic impact of vaccination even in the breakthrough cases. CoVLP+AS03 vaccine candidate was well tolerated, and no safety concerns were identified during the study. If approved by regulators, this more traditional protein+adjuvant vaccine produced using the novel plant-based platform may be able to make an important contribution to the global struggle against the increasingly complex family of SARS-CoV-2 viruses (Funded by Medicago with grants from the governments of Quebec and Canada; NCT04636697).
ABSTRACT
As the SARS-COV-2 pandemic evolves, what is expected of vaccines extends beyond efficacy to include consideration of both durability and variant cross-reactivity. This report expands on previously reported immunogenicity results from a Phase 1 trial of an AS03-adjuvanted, plant-based coronavirus-like particle (CoVLP) displaying the spike (S) glycoprotein of the ancestral SARS-CoV-2 virus in healthy adults 18-49 years of age (NCT04450004). When humoral and cellular responses against the ancestral strain were evaluated 6 months post-second dose (D201), 100% of vaccinated individuals retained binding antibodies, and [~]95% retained neutralizing antibodies; interferon gamma (IFN-{gamma}) and interleukin 4 (IL-4) responses directed against the ancestral S protein were also still detectable in [~]94% and [~]92% of vaccinees respectively. Variant-specific, cross-reactive neutralizing antibody (NAb) levels were assessed at D42 and D201 using both live wild-type and pseudovirion assays (Alpha, Beta, Gamma) or the wild-type assay alone (Delta, Omicron). In the wild-type assay, broad cross-reactivity was detected against all variants at D42 (100% Alpha and Delta, 94% Beta and Gamma, 74% Omicron). At D201, cross-reactive antibodies were detectable in almost all participants against Alpha, Gamma and Delta variants (94%) and the Beta variant (83%) and in a smaller proportion against Omicron (44%). Results were similar in the pseudovirion assay (D42, 100% cross-reactivity to Alpha and Gamma variants, 95% to Beta variant, D201, 94% for Alpha, Beta and Gamma variants). These data suggest that two doses of 3.75 {micro}g CoVLP+AS03 elicit a durable and cross-reactive response that persists for at least 6 months post-vaccination.
ABSTRACT
The rapid spread of SARS-CoV-2 continues to impact humanity on a global scale with rising total morbidity and mortality. Despite the development of several effective vaccines, new products are needed to supply ongoing demand and the needs of specific populations. We report herein a pre-specified interim analysis of the phase 2 portion of an ongoing Phase 2/3, randomized, placebo-controlled trial of a coronavirus virus-like particle (CoVLP) vaccine candidate produced in plants that displays the SARS-CoV-2 spike glycoprotein adjuvanted with AS03 (NCT04636697). A total of 753 subjects were recruited between 25 November 2020 and 24 March 2021 into three groups: Healthy Adults (18-64 years: N=306), Older Adults ([≥] 65 years: N=282) and Adults with Comorbidities ([≥]18 years: N=165) and randomized 5:1 to receive two intramuscular doses of either vaccine CoVLP (3.75 g/dose + AS03) or placebo 21 days apart. This report presents safety, tolerability and immunogenicity data collected up to 21 days after the second dose. The immune outcomes presented include neutralizing antibody (NAb) titres and cellular (IFN-{gamma} and IL-4 ELISpot) responses. In this study, CoVLP+AS03 was well-tolerated and adverse events (AE) after each dose were generally mild to moderate and transient. Solicited AEs in Older Adults and Adults with Comorbidities were generally less frequent than in Healthy Adults. CoVLP+AS03 induced seroconversion in >35% of subjects in each group after the first dose and in [~]98% of subjects 21 days after the second dose. In all treatment groups, NAb levels were [~]10-fold higher than those in a panel of convalescent sera. A significant minority ([~]20%) of subjects had evidence of a pre-existing IFN-{gamma} response to the S protein and almost all subjects in all groups (>88%) had detectable cellular responses (IFN-{gamma}, IL-4 or both) at 21 days after the second dose. A Th1-biased response was most evident after the first dose and was still present after dose two. These data demonstrated that CoVLP+AS03 will likely be well-tolerated and highly immunogenic in adults [≥]18 years of age with and without comorbidities.
ABSTRACT
Although antivirals are important tools to control the SARS-CoV-2 infection, effective vaccines are essential to control the current pandemic. Plant-derived virus-like particle (VLP) vaccine candidates have previously demonstrated immunogenicity and efficacy against influenza. Here we report the immunogenicity and protection induced in macaques by intramuscular injections of VLP bearing SARS-CoV-2 spike protein (CoVLP) vaccine candidate formulated with or without Adjuvant System 03 (AS03) or cytosine phosphoguanine (CpG) 1018. Although a single dose of unadjuvanted CoVLP vaccine candidate stimulated humoral and cell-mediated immune responses, booster immunization (at 28 days after prime) and adjuvants significantly improved both responses with a higher immunogenicity and protection provided by AS03 adjuvanted CoVLP. Fifteen microgram CoVLP adjuvanted with AS03 induced a balanced IL-2 driven response along with IL-4 expression in CD4 T cells and mobilization of CD4 follicular helper cells (Tfh). Animals were challenged by multiple routes (i.e. intratracheal, intranasal and ocular) with a total viral dose of 106 plaque forming units of SARS-CoV-2. Lower viral replication in nasal swabs and broncho-alveolar lavage (BAL) as well as fewer SARS-CoV-2 infected cells and immune cell infiltrates in the lungs concomitant with reduced levels of pro-inflammatory cytokines and chemotactic factors in BAL were observed in the animals immunized with CoVLP adjuvanted with AS03. No clinical, pathologic or virologic evidences of vaccine associated enhanced disease (VAED) were observed in vaccinated animals. CoVLP adjuvanted with AS03 was therefore selected for vaccine development and clinical trials.
