Immunity and safety of Covid‐19 synthetic minigene vaccine  Biological: injection and infusion of LV‐SMENP‐DC vaccine and antigen‐specific CTLs  China/COVID‐19  100, all, 6 months to 80 years  Treatment  Experimental: pathogen‐specific DC and CTLs patients will receive approximately 5 × 106 LV‐DC vaccine and 1 × 108 CTLs via subcutaneous injections and iv infusions, respectively  I