Shandong Province Centers for Disease Control and Prevention

This is a multicenter, open-label, partially radomized, parallel-controlled clinical trial to evaluate the safety and immunogenicity of heterologous prime-boost immunization with an aerosolised adenovirus type-5 vector-based COVID-19 vaccine (Ad5-nCoV-IH) after two-dose priming with an inactivated SARS-CoV-2 vaccine (ICV) in adults aged 18 years and above. 10420 healthy subjects aged over or equal to 18 years whom have received two doses of ICV before 6 months or more, will be recruited from six provinces in China in this study.Of them, 10000 eligible participants in an open cohort will receive a booster dose of Ad5-nCoV-IH to evaluate the safety profile. Another 420 participants were involved in immunogenicity cohort and randomized in a ratio of 1:1 to receive a boost of Ad5-nCoV-IH or ICV. The ICV homologous to the priming series will be supplied as the booster. The occurrence of adverse reactions within 28 days and serious adverse events within 6 months after vaccination will be observed in all participants. In addition, blood and saliva samples will be collected from all participants in immunogenicity cohort on the day 0 before and 14, 28 and month 3 and 6 after the booster vaccination. Each subject will remain in this study for approximately 6 months.