A Randomized Trial Comparing Omicron-Containing Boosters with the Original Covid-19 Vaccine mRNA-1273 (preprint)

BackgroundOmicron-containing bivalent boosters are available worldwide. Results of a large, randomized, active-controlled study are presented. MethodsThis phase 3, randomized, observer-blind, active-controlled trial in the United Kingdom evaluated the immunogenicity and safety of 50-g doses of omicron-BA.1-monovalent mRNA-1273.529 and bivalent mRNA-1273.214 booster vaccines compared with 50-g mRNA-1273 administered as boosters in individuals [≥]16 years. Participants had previously received 2 doses of any authorized/approved Covid-19 vaccine with or without an mRNA vaccine booster. Safety and immunogenicity were primary objectives; immunogenicity was assessed in all participants, with analysis conducted based on prior infection status. Incidence of Covid-19 post-boost was a secondary (mRNA-1273.214) or exploratory (mRNA-1273.529) objective. ResultsIn part 1 of the study, 719 participants received mRNA-1273.529 (n=362) or mRNA-1273 (n=357); in part 2, 2813 received mRNA-1273.214 (n=1418) or mRNA-1273 (n=1395). Median durations (months [range]) between the most recent Covid-19 vaccine and study boosters were similar in the mRNA-1273.529 (4.0 [1.5-8.9]) and mRNA-1273 (4.1 [3.0-5.6]) (part 1), and mRNA-1273.214 (5.5 [0.4-13.3] and mRNA-1273 (5.4 [0.2-10.6]) groups (part 2). Both mRNA-1273.529 and mRNA-1273.214 elicited superior neutralizing antibody responses against omicron BA.1 with geometric mean ratios (95% CI) of 1.68 (1.45-1.95) and 1.53 (1.41-1.67) compared to mRNA-1273 at Day 29 post-boost. Although the study was not powered to assess relative vaccine efficacy, the incidence rates/1000 person years (95% CI) of Covid-19 trended lower with mRNA-1273.529 (670.5 [528.3-839.3]) than mRNA-1273 (769.3 [615.4-950.1]) and mRNA-1273.214 (633.0 [538.1-739.7]) than mRNA-1273 (711.6 [607.5-828.5]). Sequence analysis in part 2 showed that this was driven by lower incidence of Covid-19 in the mRNA-1273.214 cohort with BA.2 and BA.4 sublineages but not BA.5 sublineages. All study boosters were well-tolerated. ConclusionThe bivalent omicron BA.1 containing booster elicited superior neutralizing antibody responses against omicron BA.1 with acceptable safety results consistent with the BA.1 monovalent vaccine. Incidence rates for Covid-19 were numerically lower in participants who received mRNA-1273.214 compared to the original booster vaccine mRNA-1273, driven by the BA.2 and BA.4 sublineages.

Efficacy of the NVX-CoV2373 Covid-19 Vaccine Against the B.1.1.7 Variant (preprint)

BackgroundCovid-19 vaccines are urgently needed, especially against emerging variants. NVX-CoV2373 is a recombinant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 rS) nanoparticle vaccine containing trimeric full-length SARS-CoV-2 spike glycoprotein and Matrix-M adjuvant. MethodsA phase 3, randomized, observer-blinded, placebo-controlled trial was conducted in adults 18-84 years old who received two intramuscular 5-{micro}g doses, 21 days apart, of NVX-CoV2373 or placebo (1:1) across 33 sites in the United Kingdom. The primary efficacy endpoint was virologically confirmed symptomatic Covid-19 with onset 7 days after second vaccination in serologically negative participants. ResultsA total of 15,187 participants were randomized, of whom 7569 received NVX-CoV2373 and 7570 received placebo; 27.2% were 65 years or older, 44.7% had comorbidities and 4.2% had baseline serological evidence of SARS-CoV-2. There were 10 cases of Covid-19 among NVX-CoV2373 recipients and 96 cases among placebo recipients, with symptom onset at least 7 days after second vaccination; NVX-CoV2373 was 89.7% (95% confidence interval, 80.2 to 94.6) effective in preventing Covid-19, with no hospitalizations or deaths reported. There were five cases of severe Covid-19, all in the placebo group. Post hoc analysis revealed efficacies of 96.4% (73.8 to 99.5) and 86.3% (71.3 to 93.5) against the prototype strain and B.1.1.7 variant, respectively. Vaccine efficacy was similar across subgroups, including participants with comorbidities and those [≥]65 years old. Reactogenicity was generally mild and transient. The incidence of serious adverse events was low and similar in the two groups. ConclusionA two-dose regimen of NVX-CoV2373 conferred 89.7% protection against a blend of prototype and variant Covid-19, demonstrated high efficacy against the B.1.1.7 variant, and had a reassuring safety profile. (Funded by Novavax, Inc. EudraCT number, 2020-004123-16).