I don't think the vaccine is the mark. But as far as believers being deceived.
When you read the King James version below, many take this to mean the "elect" can't or won't
be deceived. This is mostly because of the way certain wordings have changed in English over the 500 years.
But all of the other translations seem to say, some of the elect "can" (and will) be deceived.
Matthew 24:24
(ASV) For there shall arise false Christs, and false prophets, and shall show great signs and wonders; so as to lead astray, if possible, even the elect.
(BBE) For there will come up false Christs, and false prophets, who will do great signs and wonders; so that if possible even the saints might be tricked.
(ESV) For false christs and false prophets will arise and perform great signs and wonders, so as to lead astray, if possible, even the elect.
(ESV+) For R7false christs and R8false prophets will arise and R9perform great signs and wonders, R8so as to lead astray, if possible, even the elect.
(GNB) For false Messiahs and false prophets will appear; they will perform great miracles and wonders in order to deceive even God's chosen people, if possible.
(GW) False messiahs and false prophets will appear. They will work spectacular, miraculous signs and do wonderful things to deceive, if possible, even those whom God has chosen.
(ISV) because false messiahs and false prophets will appear and display great signs and wonders to deceive, if possible, even the elect.
(KJV) For there shall arise false Christs, and false prophets, and shall shew great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect.
(MKJV) For false Christs and false prophets will arise and show great signs and wonders; so much so that, if it were possible, they would deceive even the elect.
(NAS77) "For false Christs and false prophets will arise and will show great signs and wonders, so as to mislead, if possible, even the elect.
(NAS95) "For false Christs and false prophets will arise and will show great signs and wonders, so as to mislead, if possible, even the elect.
(NIrV) False Christs and false prophets will appear. They will do great signs and miracles. They will try to fool God's chosen people if possible.
(NIV) For false messiahs and false prophets will appear and perform great signs and wonders to deceive, if possible, even the elect.
(NKJV) For false christs and false prophets will rise and show great signs and wonders to deceive, if possible, even the elect.
(NLT) For false messiahs and false prophets will rise up and perform great signs and wonders so as to deceive, if possible, even God’s chosen ones.
(TPT) For there will be imposters falsely claiming to be God’s ‘Anointed One,’ and false prophets will arise to perform miracle signs to lead astray, if possible, those God has chosen to be his.