A clinical trial of a recombinant novel coronavirus variant vaccine (adenovirus type 5 vector) for inhalation in adults 18 years of age and older

INTERVENTION: Group 1:Nebulized inhalation device for oral inhalation of test vaccine 1; immunization dose: 0.1 ml/visit;Group 2:Nebulized inhalation device transoral inhalation test vaccine 2; immunization dose: 0.1 ml/visit;Group 3:Nebulized inhalation device for transoral inhalation of control vaccine; immunization dose: 0.1 ml/visit; CONDITION: diseases caused by novel coronavirus (SARS‐CoV‐2) infection (COVID‐19) PRIMARY OUTCOME: Geometric mean titer (GMT) of anti‐Omicron‐specific neutralizing antibodies (true virus) on day 28 post‐immunization, positive conversion rate (>= 4‐fold increase compared to pre‐immunization);Incidence of adverse reactions (AR) within 0 to 28 days after immunization; SECONDARY OUTCOME: Incidence of adverse reactions 30 min after immunization;Incidence of adverse reactions/adverse events within 14 days after immunization;Incidence of adverse events within 28 days after exemption;Incidence of serious adverse events (SAE) within 6 months after vaccination;GMT, positive conversion rate (>=4 times higher than before) and GMI of antigen‐specific neutralizing antibody (true virus) on day 28 after exemption;Anti‐Omicron specific neutralizing antibody (true virus) GMI on day 28 after immunization;Positive conversion rate (>=4 times higher than before exemption), GMT and GMI of anti‐Omicron and proto‐strain specific neutralizing antibody (true virus) at 14 days, 3 months and 6 months after exemption;Positive conversion rate (>=4 times higher than before), GMC and GMI of anti‐Omicron and S‐RBD IgG at 14 days, 28 days, 3 months and 6 months after immunization;Stratification of anti‐Omicron and proto‐viral strain‐specific neutralizing antibodies (true virus) and anti‐Omicron and proto‐viral strain S‐RBD IgG based on pre‐immune Ad5 levels;GMT, positive conversion rate, GMI for partial VOC/VOI cross‐neutralization on day 28 after exemption; INCLUSION CRITERIA: 1. Volunteers are 18 years of age or older at the time of screening. 2. Informed consent was obtained from the volunteers and the volunteers or witnesses were able to sign the informed consent form. 3. Volunteers are able and willing to comply with the requirements of the clinical trial protocol and are able to complete the 6‐month study follow‐up. 4. Have completed 3 doses of novel inactivated coronavirus vaccine with an interval of >=3 months between the last dose and enrollment. 5. Provide proof of negative nucleic acid within 48h at the time of screening.