inclusion criteria: volunteers aged 18 and above at the time of screening; obtain the informed consent of the volunteers and sign the informed consent; volunteers are able and willing to comply with the requirements of the clinical trial protocol and complete the 6-month study follow-up; have received 3 doses of sinovac/beijing biological novel coronavirus inactivated vaccine with an interval of 6-9 months.

inclusion criteria: volunteers aged 18 and above at the time of screening; obtain the informed consent of the volunteers and sign the informed consent; volunteers are able and willing to comply with the requirements of the clinical trial protocol and complete the 6-month study follow-up; have received 3 doses of sinovac/beijing biological novel coronavirus inactivated vaccine with an interval of 6-9 months.