Recombinant protein COVID-19 vaccine (bivalent) (WestVac Biopharma)

This is a randomized, phase Ⅱ, single-blind, randomized, parallel-group controlled clinical trial.
The study plans to enroll subjects who have completed homologous primary vaccination with either inactivated or mRNA or Viral Vector COVID-19 vaccines (one or two doses) and have not been infected with COVID-19. All subjects will be evaluated for safety and immunogenicity after a single dose booster immunization with Recombinant COVID-19 variant Vaccine (Sf9 Cell) or inactivated COVID-19 vaccine (Vero cell) or mRNA vaccine or Viral Vector vaccine.