For Democratic candidates, the virus is a bit like January 6; it depends on the quality of the GOP opposition. If the Republican candidate is a militant anti-vaxxer, that issue should be featured prominently in the campaign; whip up the anger of the pro-vax majority by accusing your opponent of depriving responsible citizens of their freedom and having blood on his hands. If he isn’t, then you’re probably better off letting it drop. There is no real advantage to bringing it up.