inclusion criteria: axillary temperature ≤37.0 ℃. aged 18 years and above, after 3, 4, 5, or 6 months since finished two doses schedule of coronavac or bbibp-corv, or one does coronavac and one does bbibp-corv. proven legal identity, could come each visit. participants should understand the contents of the informed consent form, the vaccine in this trial, voluntarily sign the informed consent form.

inclusion criteria: axillary temperature ≤37.0 ℃. aged 18 years and above, after 3, 4, 5, or 6 months since finished two doses schedule of coronavac or bbibp-corv, or one does coronavac and one does bbibp-corv. proven legal identity, could come each visit. participants should understand the contents of the informed consent form, the vaccine in this trial, voluntarily sign the informed consent form.