I'm adding vaxed, vaxes and vaxing. Also vaxx, vaxxes, vaxxed and vaxxing.
Wiktionary has vax, as both a noun, for vaccine, and a verb, for vaccinate. It also has the alternate form vaxx and its inflections.
The online Oxford has vax, as US informal for a vaccine or vaccination, but not as a verb, so it wouldn't recognise vaxed.
All these words have been used a lot in the past 12 months or so, for obvious reasons. Why the double-X versions, I don't know. Nobody would write that they "faxxed a document". But it could be that the earliest use of vaxxed was as the title of the anti-vaccination film I mentioned in the previous post. The producers probably thought it looked more sinister. (A double-cross?) It could also be a back-formation from anti-vaxxer. In any case, the double-X variants are nowadays used by writers without any anti-vaccination message.
I gave some thought to whether some of these words ought to be classed as common. I think you could certainly say that the single-X words are quite common at present, but maybe in a year or two they'll fall out of use. I'm making all these words rare for now, but that could change.