A SARS-CoV-2 recombinant spike protein vaccine (S-268019-b) for COVID-19 prevention during the Omicron-dominant period: A phase 3, randomised, placebo-controlled clinical trial

Vu Dinh Thiem; Pham Thi Van Anh; Chu Van Men; Do Thai Hung; Andrew J Pollard; Akari Kamitani; Yukio Tada; Hidenori Fukuyama; Yuka Iwasaki; Mari Ariyasu; Takuhiro Sonoyama

doi:10.1016/j.vaccine.2024.04.084

A SARS-CoV-2 recombinant spike protein vaccine (S-268019-b) for COVID-19 prevention during the Omicron-dominant period: A phase 3, randomised, placebo-controlled clinical trial

Vaccine. 2024 May 10:S0264-410X(24)00523-1. doi: 10.1016/j.vaccine.2024.04.084. Online ahead of print.

Authors

Affiliations

¹ Centre for Clinical Trials, National Institute of Hygiene and Epidemiology, Ha Noi, Viet Nam.
² Ha Noi Medical University, Ha Noi, Viet Nam.
³ Viet Nam Military Medical University, Ha Noi, Viet Nam.
⁴ Pasteur Institute in Nha Trang, Khanh Hoa, Viet Nam.
⁵ Oxford Vaccine Group, Department of Paediatrics, University of Oxford and the NIHR Oxford Biomedical Research Centre, Oxford, UK.
⁶ Shionogi & Co., Ltd., Osaka, Japan.
⁷ Shionogi & Co., Ltd., Osaka, Japan. Electronic address: mari.tatsuno@shionogi.co.jp.

PMID: 38734495
DOI: 10.1016/j.vaccine.2024.04.084

Abstract

Clinical trials of new vaccines based on existing variants of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) are often impacted by the emergence of new virus variants. We evaluated the efficacy, immunogenicity, and safety of S-268019-b, a recombinant spike protein subunit vaccine based on the ancestral strain, for preventing symptomatic coronavirus disease 2019 (COVID-19) during the Omicron (BA.2)-dominant period in Vietnam. In this multicentre, phase 3, randomised (2:1), observer-blind, placebo-controlled crossover study, participants received 2 intramuscular doses (28 days apart) of either 10 µg of S-268019-b (Recombinant S-protein vaccine) or placebo. The primary endpoint was incidence of laboratory-confirmed symptomatic COVID-19 before crossover, with onset within 14 days following the second dose, in participants who were seronegative and reverse transcription polymerase chain reaction (RT-PCR)-negative at baseline. The secondary endpoints included immunogenicity and safety. In total, 8,594 participants were randomised (S-268019-b [n = 5,727]; placebo [n = 2,867]). Vaccine efficacy versus placebo was 39·1 % (95 % confidence interval [CI]:26·6-49·5; one-sided P = 0·0723). The incidence rate (95 % CI) of symptomatic COVID-19 was 776·41/1,000 person-years (682·04-880·19) in the S-268019-b group and 1272·87/1,000 person-years (1101·32-1463·57) in the placebo group. The geometric mean titres (95 % CI) of the SARS-CoV-2 neutralising antibody increased on Day 57 versus baseline with S-268019-b (34·66 [27·04-44·41] versus 2·50 (non-estimable) but not with placebo. There were no safety concerns regarding S-268019-b. S-268019-b did not demonstrate the targeted efficacy threshold against symptomatic COVID-19; however, findings were comparable with other prophylactic vaccines based on ancestor strain during the Omicron-dominant period. S-268019-b demonstrated immunogenicity and was well-tolerated. ClinicalTrials.gov identifier: NCT05212948.

Keywords: COVID-19 vaccine; Recombinant spike protein subunit vaccine; S-268019-b; SARS-CoV-2; Vaccine efficacy; Vietnam.

Associated data

ClinicalTrials.gov/NCT05212948