1. The participants were 18 to 75 years old, male or female, 2. Two doses of inactivated SARS-CoV-2 vaccine were administered recently and the interval between two doses was 3-5 weeks, 3. The neutralization antibody levels were negative or less than 20% average antibody level of COVID-19 recovered patients in 14 days after administering two doses of SARS-CoV-2 vaccine, 4. It is now in 4-24 weeks after administering second dose of SARS-CoV-2 vaccine, 5. Participants can follow the researchers guidance to accomplish the research process.

1. The participants were 18 to 75 years old, male or female, 2. Two doses of inactivated SARS-CoV-2 vaccine were administered recently and the interval between two doses was 3-5 weeks, 3. The neutralization antibody levels were negative or less than 20% average antibody level of COVID-19 recovered patients in 14 days after administering two doses of SARS-CoV-2 vaccine, 4. It is now in 4-24 weeks after administering second dose of SARS-CoV-2 vaccine, 5. Participants can follow the researchers guidance to accomplish the research process.