The goal of this clinical trial is to learn if the SARS-CoV-2 subunit mucosal vaccine with the recombinant flagellin protein adjuvant works to Prevent COVID-19 infection. It will also learn about the Safety and immunogenicity of the vaccine.
The subjects are healthy individuals aged between 18 and 65 years old (inclusive), with no gender preference, ensuring an appropriate gender ratio.
Have received 2-3 doses of COVID-19 inactivated vaccine, and the last dose was administered more than 6 months ago.
Have not been infected with COVID-19 within 3 months.
Capable of being used in conjunction with nasal sprays, and also suitable for nasal irrigation, saliva collection, and blood collection.
Active or suspected viral, bacterial, fungal, or parasitic infections, including herpes, shingles, or cold sores, within 14 days prior to screening.
History of recurrent infections of unknown causes; or use of systemic antibiotics within 90 days prior to drug administration.
Individuals with malignant tumors or a history of malignant tumors, except for non-melanoma skin cancer that has been cured for more than 3 years.
Nasal malformation, trauma, or other reasons that make it impossible to use nasal sprays.