SARS-CoV-2 strain (WIV04 strain) was isolated from a patient at the Jinyintan Hospital in Wuhan. The cells were cultivated and the supernatant was treated with β-propiolactone to inactivate the virus. β-propiolactone is a chemical disinfectant and used as a sterilization technique, it is an alkylating agent that interacts with DNA. The cellular debris was ultra-filtered out and the vaccine was treated again with β-propiolactone. Finally, the vaccine was adsorbed onto 0.5 mg aluminum hydroxide and loaded into 0.5mL syringes with sterile phosphate-buffered saline. The placebo groups contained only the sterile buffer and the aluminum hydroxide adjuvant.

• https://pubchem.ncbi.nlm.nih.gov/compound/beta-Propiolactone#section=Metabolism-Metabolites