Personally, I think those people are as nuts as the anti-vaccine crowd, but it's something that you will have to contend with at resale time.

Some of the things I ask for include copies of DL, pay stubs, past rental references, proof of renters insurance, and copies of vaccination/rabies certificates for dogs (after I’ve met their pets).

Again, which will pay for nothing . . .Double-check, put/get everything in writing, keep records that the pet's been properly vaccinated &/or licensed as required by whatever area you're in & keep on top of ongoing damages.

Also add 'all animals to be fixed, licensed and vaccinated'. 

For future or prospective tenants, adopt a pet/animal policy for every tenant including requiring local licensing/ID tag (some counties/issuing agencies will require up to date rabies vaccine before issuing the license/ID tag plus there is a fee to be paid), renter's insurance with no exclusion of the pet/animal's breed, neuter, annual vet examination of the pet/animal and up to date shots with proof sent to you etc.

No vaccine yet, everyone was getting sick.

With that being said, you can require masks at showings or proof of vaccines if you want to keep everyone safe.

She is a single mom with a child and she lost her job because she was in the healthcare industry and didn't want to get vaccinated (I will withhold my personal opinions on that).  

Vaccination deaths are on the rise, however. 

Sometimes these can take four to six months because they have to space out the vaccinations.