There are remarkably few mamallian species with > 1m population. Virtually all are grazing animals, sea mammals, or rodents.
I'm not sure what species SARS-COV-2 is compatible with, though I've mostly heard of animals > 5kg mass (e.g., domesticated cats, dogs, deer, wildcats), with the very notable exception of bats.
The virus has been detected in 20--40% of sampled deer in the US in multiple states, which is a particularly bad sign.
If it's gained foothold in rodent populations ... well, it could be around for a while.
From April of 2021:
Results obtained from experimental studies indicate that animal species such as cats, ferrets, raccoon dogs, cynomolgus macaques, rhesus macaques, white-tailed deer, rabbits, Egyptian fruit bats, and Syrian hamsters are susceptible to SARS-CoV-2 infection, and that cat-to-cat and ferret-to-ferret transmission can take place via contact and air. However, natural infections of SARS-CoV-2 have been reported only in pet dogs and cats, tigers, lions, snow leopards, pumas, and gorillas at zoos, and farmed mink and ferrets. Even though human-to-animal spillover has been reported at several instances, SARS-CoV-2 transmission from animals-to-humans has only been reported from mink-to-humans in mink farms.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8128218/?report...
That's not to say that broader transmission isn't possible (the abstract doesn't mention deer, and I'm aware they're found to be infected). The science is still being established.
We could vaccinate all of those. If we needed to do the last 4% of wild animals, I'm betting we could vaccinate more than half of those too.