inclusion criteria: 1. healthy participants aged 18 years and older who have completed the second dose of 2-dose regimen of sars-cov-2 vaccine (vero cell) inactivated in the past 3 months; 2. voluntarily participate in the study and sign the informed consent form, who can provide valid id and follow the study protocol requirement; 3. in the past 14 days, no history of high or medium risk of the epidemic, overseas travel history or residence history; no history of contact with confirmed, asymptomatic or suspected covid-19 cases; no history of contact with the persons from high- and medium-risk epidemic areas or contact patients with fever or respiratory symptoms; and those who are not in isolation period. 4. males of reproductive potential and females of childbearing potential voluntarily agree to take effective and acceptable contraceptive methods from the signing of informed consent form to 3 months after vaccination.

inclusion criteria: 1. healthy participants aged 18 years and older who have completed the second dose of 2-dose regimen of sars-cov-2 vaccine (vero cell) inactivated in the past 3 months; 2. voluntarily participate in the study and sign the informed consent form, who can provide valid id and follow the study protocol requirement; 3. in the past 14 days, no history of high or medium risk of the epidemic, overseas travel history or residence history; no history of contact with confirmed, asymptomatic or suspected covid-19 cases; no history of contact with the persons from high- and medium-risk epidemic areas or contact patients with fever or respiratory symptoms; and those who are not in isolation period. 4. males of reproductive potential and females of childbearing potential voluntarily agree to take effective and acceptable contraceptive methods from the signing of informed consent form to 3 months after vaccination.

inclusion criteria: healthy participants aged 18 years and older who have completed the second dose of 2-dose regimen of sars-cov-2 vaccine (vero cell) inactivated in the past 3 months; voluntarily participate in the study and sign the informed consent form, who can provide valid id and follow the study protocol requirement; in the past 14 days, no history of high or medium risk of the epidemic, overseas travel history or residence history; no history of contact with confirmed, asymptomatic or suspected covid-19 cases; no history of contact with the persons from high- and medium-risk epidemic areas or contact patients with fever or respiratory symptoms; and those who are not in isolation period. males of reproductive potential and females of childbearing potential voluntarily agree to take effective and acceptable contraceptive methods from the signing of informed consent form to 3 months after vaccination.

inclusion criteria: healthy participants aged 18 years and older who have completed the second dose of 2-dose regimen of sars-cov-2 vaccine (vero cell) inactivated in the past 3 months; voluntarily participate in the study and sign the informed consent form, who can provide valid id and follow the study protocol requirement; in the past 14 days, no history of high or medium risk of the epidemic, overseas travel history or residence history; no history of contact with confirmed, asymptomatic or suspected covid-19 cases; no history of contact with the persons from high- and medium-risk epidemic areas or contact patients with fever or respiratory symptoms; and those who are not in isolation period. males of reproductive potential and females of childbearing potential voluntarily agree to take effective and acceptable contraceptive methods from the signing of informed consent form to 3 months after vaccination.