Seems like a ploy to get the "uneducated" on board to take the shot. Along the lines of "Hey, if Charles Barkley wants it, it MUST be good."
If Charles Barkley is so sure he wants the vaccine he's welcome to take it. I'd bet there are thousands of health care drones and prisoners in nursing homes (on death row for the crime of being old and dependent) who'd be glad to let him have theirs. At least he could pay for the non-stop care he'll need afterwards.