Schematic drawing of 8 platform strategies used for the development of COVID-19 vaccines, and the pathway each one follows to induce T cell and B cell immune response. The strategies include live-attenuated vaccine (LA), inactivated vaccine (IA), DNA vaccine (DNA), RNA vaccine (RNA), viral vector replicating vaccine (VVR), viral vector nonreplicating (VVNR), virus-like particles (VLP), and subunit vaccine (Subunit). CV, coronavirus; APC, antigen processing cell.