This is a randomized, double-blinded, placebo-controlled study which comprises two parts, (dose escalation part and dose expansion part), and each volunteer will only be invited to join either one part. The duration of each part is around one (1) year, including screening, dosing and follow up visits.
To investigate the safety and immunogenicity profile of of a novel nasal spray investigational vaccine, which is a potential prophylactic vaccine for current pandemic disease COVID-19.