inclusion criteria: 1. male or female aged ≥12 years old when signing icf; 2. participants who were fully vaccinated (2 doses) with inactivated covid-19 vaccine (sinopharm covid-19 vaccine) and the interval between the last dose and this study vaccination is ≥3 months and ≤12 months; 3. the participant and/or his legal guardian and/or his entrusted person can sign written icf, and can fully understand the trial procedure, the risk of participating in the trial, and other interventions that can be selected if they do not participate in the trial; 4. the subject and/or his legal guardian and/or his entrusted person have the ability to read, understand, and fill in record cards; 5. healthy participants or participants with pre-existing medical conditions who are in stable condition. the "pre-existing medical conditions" include but not limited to hypertension, diabetes, chronic cholecystitis and cholelithiasis, chronic gastritis that meet the described criteria. a stable medical condition is defined as disease not requiring significant change in therapy or no need for hospitalization as a consequence of worsening disease state for at least 3 months prior to enrollment; 6. fertile men and women of childbearing age voluntarily agree to take effective contraceptive measures from signing icf to 6 months after the study vaccination; the pregnancy test results of women of childbearing age are negative on screening.

inclusion criteria: 1. male or female aged ≥12 years old when signing icf; 2. participants who were fully vaccinated (2 doses) with inactivated covid-19 vaccine (sinopharm covid-19 vaccine) and the interval between the last dose and this study vaccination is ≥3 months and ≤12 months; 3. the participant and/or his legal guardian and/or his entrusted person can sign written icf, and can fully understand the trial procedure, the risk of participating in the trial, and other interventions that can be selected if they do not participate in the trial; 4. the subject and/or his legal guardian and/or his entrusted person have the ability to read, understand, and fill in record cards; 5. healthy participants or participants with pre-existing medical conditions who are in stable condition. the "pre-existing medical conditions" include but not limited to hypertension, diabetes, chronic cholecystitis and cholelithiasis, chronic gastritis that meet the described criteria. a stable medical condition is defined as disease not requiring significant change in therapy or no need for hospitalization as a consequence of worsening disease state for at least 3 months prior to enrollment; 6. fertile men and women of childbearing age voluntarily agree to take effective contraceptive measures from signing icf to 6 months after the study vaccination; the pregnancy test results of women of childbearing age are negative on screening.

inclusion criteria: male or female aged ≥12 years old when signing icf; participants who were fully vaccinated (2 doses) with inactivated covid-19 vaccine (sinopharm covid-19 vaccine) and the interval between the last dose and this study vaccination is ≥3 months and ≤12 months; the participant and/or his legal guardian and/or his entrusted person can sign written icf, and can fully understand the trial procedure, the risk of participating in the trial, and other interventions that can be selected if they do not participate in the trial; the subject and/or his legal guardian and/or his entrusted person have the ability to read, understand, and fill in record cards; healthy participants or participants with pre-existing medical conditions who are in stable condition. the "pre-existing medical conditions" include but not limited to hypertension, diabetes, chronic cholecystitis and cholelithiasis, chronic gastritis that meet the described criteria. a stable medical condition is defined as disease not requiring significant change in therapy or no need for hospitalization as a consequence of worsening disease state for at least 3 months prior to enrollment; fertile men and women of childbearing age voluntarily agree to take effective contraceptive measures from signing icf to 6 months after the study vaccination; the pregnancy test results of women of childbearing age are negative on screening.

inclusion criteria: male or female aged ≥12 years old when signing icf; participants who were fully vaccinated (2 doses) with inactivated covid-19 vaccine (sinopharm covid-19 vaccine) and the interval between the last dose and this study vaccination is ≥3 months and ≤12 months; the participant and/or his legal guardian and/or his entrusted person can sign written icf, and can fully understand the trial procedure, the risk of participating in the trial, and other interventions that can be selected if they do not participate in the trial; the subject and/or his legal guardian and/or his entrusted person have the ability to read, understand, and fill in record cards; healthy participants or participants with pre-existing medical conditions who are in stable condition. the "pre-existing medical conditions" include but not limited to hypertension, diabetes, chronic cholecystitis and cholelithiasis, chronic gastritis that meet the described criteria. a stable medical condition is defined as disease not requiring significant change in therapy or no need for hospitalization as a consequence of worsening disease state for at least 3 months prior to enrollment; fertile men and women of childbearing age voluntarily agree to take effective contraceptive measures from signing icf to 6 months after the study vaccination; the pregnancy test results of women of childbearing age are negative on screening.