The mark of the beast cannot be a vaccine. Since those with the mark are damned, and irretrivably so, accepting the mark of the beast must be a mortal sin and a deliberate choice or act against God.
In the case of a vaccine there would be stupid, ignorant, mentally handicapped people who would be ''marked by the beast' thinking they were just being vaccinated against the Kung Flu. God would therefore have to damn them to Hell for being ignorant.
Revelation is clear that no-one with the mark of the beast is saved. So a vaccine cannot be it.
Not unless people are explicitly asked to agree to obey the government and worship Satan/deny God in order to get the vaccine and buy and sell anything. Wanting to avoid a real or supposed virus, wanting to buy and sell, and not being an anti-vaxxer, are not mortal sins.
Continuing thoughts...
A few people still think the Social Security Number is the mark of the beast
https://www.forbes.com/sites/peterjreilly/2014/07/16/social-security-number-may-be-mark-of-the-beast-but-that-will-not-save-your-job/#1ae1ad754fc1.
But even if IT were imprinted from the very start by a indelible stamp on your hand accepting it would not have been one and the same as accepting Satan or worshiping him, unless that were the clear agreement when accepting it.
Fight the vaccine being maybe dangerous to physical health, or its stamp being an invasion of privacy. Fight the evil or imprudent men who rush things, or suppress inexpensive remedies or exaggerate numbers. But any mark(s) left by a vaccine are not "of the beast" unless a man's free will knowingly worships SATAN in accepting it. NOT accepting (even mistakenly) something to help his health OR even to buy and sell. But agreeing to obey SATAN and not GOD.
Fight a vaccine mandate if it makes sense. But making "it's the mark of the beast" as the argument, is just outlandish and stirs up fear in some and ridicule in others.