This was a phase II, randomized, placebo-controlled, observer-blinded study of the safety and immunogenicity of SARS-CoV-2 messenger RNA (mRNA) vaccine (BNT162b2) in Chinese healthy population. After randomization, the trial for each participant lasted for approximately 13 months. Screening period was 2 weeks prior to randomization (Day -14 to Day 0), and two doses of either SARS-CoV-2 vaccine (BNT162b2) or placebo were given intramuscularly (IM) separated by 21 days.

Inclusion Criteria:

• Male or female participants between the ages of 18 and 85 years, inclusive, at randomization.
• Participants who were willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures.
• Healthy participants who were determined by medical history, physical examination (if required), and clinical judgment of the investigator to be eligible for inclusion in the study. Note: Healthy participants with preexisting stable disease, defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 6 weeks before enrollment, were allowed to be included.
• Capable of giving personal signed informed consent, which included compliance with the requirements and restrictions listed in the informed consent form and the protocol.
• SARS-CoV-2 antibody test screening was negative.
• Negative SARS-CoV-2 test in throat swabs by reverse transcription-polymerase chain reaction (RT-PCR) (only for the first approximately 150 subjects).
• Normal in chest computed tomography (CT) scans (no imaging features of coronavirus disease 2019 (COVID-19), only for the first approximately 150 subjects).

Exclusion Criteria:

• Other medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study.
• Known infection with human immunodeficiency virus (HIV), hepatitis C virus (HCV), or hepatitis B virus (HBV).
• History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (eg, anaphylaxis) to any component of the study intervention(s).
• Receipt of medications intended to prevent COVID-19.
• Immunocompromised individuals with known or suspected immunodeficiency, determined by history and/or laboratory/physical examination.
• Bleeding diathesis or condition associated with prolonged bleeding that would, in the opinion of the investigator, contraindicate intramuscular injection.
• Women who were pregnant or breastfeeding.
• Previous vaccination with any coronavirus vaccine.
• Individuals who received treatment with immunosuppressive therapy, including cytotoxic agents or systemic corticosteroids, eg, for cancer or an autoimmune disease, or planned receipt throughout the study. If systemic corticosteroids have been administered short term (<14 days) for treatment of an acute illness, participants should not be enrolled into the study until corticosteroid therapy has been discontinued for at least 28 days before study intervention administration. Inhaled/nebulized, intra-articular, intrabursal, or topical (skin or eyes) corticosteroids were permitted.
• Receipt of blood/plasma products or immunoglobulin, from 60 days before study intervention administration or planned receipt throughout the study.
• Participation in other studies involving study intervention within 28 days prior to study entry and/or during study participation.
• Previous participation in other studies involving study intervention containing lipid nanoparticles.
• Have had contact with confirmed COVID-19 patients or persons tested positive for SARS-CoV-2 within the 30 days prior to Screening Visit.
• Travel or live in any country or region with a high SARS-CoV-2 infection risk (as defined at Screening Visit) within the 14 days prior to Screening Visit.
• Symptoms of COVID-19, e.g., respiratory symptoms, fever, cough, shortness of breath and breathing difficulties.
• Fever, defined as axillary temperature ≥37.3ºC or oral temperature ≥38ºC.
• History of SARS, SARS-CoV-2 or middle east respiratory syndrome (MERS) infection. Suspected SARS patients should be screened for SARS antibodies.
• Investigator site staff or Fosun employees directly involved in the conduct of the study, site staff otherwise supervised by the investigator, and their respective family members.