The mean age of participants was 36.1; 58.4% were males, and 32.2% had high-risk medical conditions. About 75% of participants were non-naïve at enrolment. Within the modified full analysis set, 121 cases of symptomatic COVID-19 were reported ≥ 14 days after the second dose, and the overall vaccine effectiveness was 64.7%. Placebo recipients showed a higher cumulative incidence of COVID-19 than vaccinees.
Taken together, the trial met the primary objective, demonstrating efficacy against symptomatic COVID-19. The effectiveness of 75.9% against symptomatic disease in non-naïve subjects is particularly relevant. The findings suggest the vaccine could be a potential booster at a time when most of the population is already exposed to the virus or vaccinated.
In a recent study published in The Lancet Respiratory Medicine, researchers evaluated the efficacy of a bivalent recombinant protein vaccine for coronavirus disease 2019 (COVID-19).
Vaccine efficacy was generally higher in males. The causal variant was determined in 68 cases, with the Omicron sub-variants (BA.1 and BA.2) causing 64 cases. The Omicron-specific efficacy was 72.5% in all subjects, 20.4% in naïve participants, and 93.9% in non-naïve individuals. There were five cases of the Delta variant, all in placebo recipients. Seven placebo recipients and four vaccinees had immediate unsolicited adverse events.
Participants were recruited from eight countries between October 19, 2021, and February 15, 2022. Eligible subjects were non-vaccinated adults aged 18 or older. Data on medical history and race/ethnicity were self-reported at enrolment. Participants were randomized to receive the vaccine or placebo. The vaccine group received 0.5 ml injections containing 5 μg D614 and 5 μg B.1.351 antigens at days 1 and 22.
In the present study, researchers presented data on the clinical safety and efficacy of the bivalent CoV2 preS dTM-AS03 (D614 + B.1.351) vaccine as the primary series. This randomized, double-blind, phase 3, placebo-controlled trial had two stages. The first stage evaluated the efficacy of a prototype monovalent vaccine, and the second stage explored the bivalent vaccine. Data from the second stage were reported in this study.
Study: Efficacy of a bivalent (D614 + B.1.351) SARS-CoV-2 recombinant protein vaccine with AS03 adjuvant in adults: a phase 3, parallel, randomised, modified double-blind, placebo-controlled trial. Image Credit: Dmitry Kovalchuk / Shutterstock
About the study
- Dayan GH, Rouphael N, Walsh SR, et al. Efficacy of a bivalent (D614 + B.1.351) SARS-CoV-2 recombinant protein vaccine with AS03 adjuvant in adults: a phase 3, parallel, randomized, modified double-blind, placebo-controlled trial. The Lancet Respiratory Medicine, 2023, DOI: 10.1016/S2213-2600(23)00263-1, https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(23)00263-1/fulltext
Five cases developed severe illness, 12 had moderate or worse illness, and two subjects required hospitalization. No deaths occurred due to COVID-19. Vaccine efficacy against symptomatic disease in non-naïve subjects was over 75%, but 30.9% in naïve subjects. Overall, the efficacy against symptomatic illness was 60.3% after the first dose. Efficacy against asymptomatic infection was 1.2%.
The placebo group received 0.9% normal saline. Nasopharyngeal swabs and blood specimens were obtained before each vaccination. Participants were contacted weekly to determine if they tested COVID-19-positive or had symptoms of a COVID-19-like illness. Naïve and non-naïve status was ascertained by electrochemiluminescence immunoassays.