Study design and participants
respiratory disease, anaphylaxis, diabetes; neurologic illness, SARS-CoV-2 infection, fever, infection, hypertension
RESPIRATORY DISEASE, ANAPHYLAXIS, SARS-COV-2 INFECTION, CARDIOVASCULAR DISEASE, INFECTION, HYPERTENSION, DISEASES, DISEASE
A single-center, randomized, parallel-controlled prospective cohort study of a second booster dose (or fourth vaccine dose) with a heterologous booster (Ad5-nCoV) or a homologous booster (inactivated SARS-CoV-2 vaccine) was conducted in Xihu District, Hangzhou City, Zhejiang Province, China. Participants aged ≥18 years with stable medical conditions who had completed a three-dose regime of the inactivated SARS-CoV-2 vaccine (CoronaVac or Covilo) 6 months earlier were recruited from the community.A screening visit before the participants were enrolled allowed exclusion of the following conditions: history of infection with SARS-CoV-2; pregnant or lactating; use of immunosuppressives; fever; history of severe anaphylaxis to vaccines; severe and/or uncontrolled respiratory disease and cardiovascular disease; hypertension (systolic pressure ≥ 180 mmHg/diastolic pressure ≥ 110 mmHg); diabetes; neurologic illness; and other underlying diseases that could interfere with the evaluation of the primary study endpoints. Previous SARS-CoV-2 infection history was confirmed with participant recall and by checking participants’ recent medical visits.The Research Ethics Committee of the Zhejiang Provincial Center of Disease Control and Prevention reviewed and approved the study protocol. The informed consent form was signed by all participants before enrolment.