A PHASE 4, RANDOMIZED, DOUBLE-BLIND, THIRD-PARTY-UNBLINDED STUDY TO INVESTIGATE THE SAFETY AND TOLERABILITY OF A BNT162B2 RNA-BASED, VARIANT-ADAPTED VACCINE CANDIDATE AGAINST SARS-COV-2 AND EVALUATE THE CIRCULATING SARS-COV-2 SPIKE PROTEIN LEVEL IN HEALTHY PARTICIPANTS 18 THROUGH 64 YEARS OF AGE | Arctuva