Study Design and Participants:

• Trials conducted in Henan Providence, China
• Double-blind, randomized, placebo-controlled Phase I and Phase II trials
• Participants: aged 18 to 59 years, no history of SARS-CoV (on-site inquiry) or SARS-CoV-2 (serological and nucleic acid test)
• Phase I Design: 96 participants, 3 vaccine dose groups (low 2.5 μg, medium 5 μg, and high 10 μg antigen protein content per dose) and a control group (received aluminum hydroxide adjuvant only), ratio of vaccine to placebo was 3:1, received intramuscular injections on days 0, 28, and 56.
• Phase II Design: 224 participants, 2 schedule groups that both received the 5 μg vaccine (days 0 and 14, and days 0 and 21), the vaccine to placebo ratio was 3:1.
• Sequential enrollment and sentinel data were used to keep the participants safe. The low dose in Phase I was used first and monitored for 7 days for adverse reactions. The medium dose group only received vaccines if there were no vaccine-related reactions in those 7 days, and the same procedure was followed for the high dose group and the phase II medium dose vaccinations.