FAQ: Must We Vaccinate All Foster Animals?

Here is a common question about vaccinating foster animals answered by ASPCA Shelter Medicine Services veterinarians.

Q: We get a lot of bottle kittens, and they of course spend a long time in foster care until they’re old enough for spay/neuter and adoption around 8 weeks of age.

In the past it’s been very expensive for us to keep giving them booster vaccines every two weeks like we do for the shelter animals, and it’s also been really hard to get the foster caregivers to keep bringing them back in that frequently. Since they’re in homes, is that really necessary?  Can we start giving foster kittens the vaccines later or give them less often?

A: Vaccination protocols for animals in foster care are often a source of confusion, because foster homes don’t always seem to fit neatly in the two sets of guidelines that exist. For both cats and dogs, there are distinct recommendations for owned pets and those housed in shelter environments.

Animals in shelters are often housed in high-density environments, may have received little to no preventive care prior to intake, and are generally at much higher risk of exposure to infectious disease. For all these reasons, the risks of not vaccinating are much higher than they would be for a typical pet in a home. We generally vaccinate shelter animals starting at a younger age with more frequent boosters to minimize the time they will be unprotected. We also vaccinate animals with certain conditions—like an upper respiratory tract infection or even pregnancy—that might make us otherwise delay vaccines.

So where does a foster home fall? There are foster homes that care for multiple animals at any given time and on a near continuous basis, and they may take in animals who are sick or incubating infectious diseases. Then there are newbie foster homes—maybe this is their first or second foster animal and their environment is a bit closer to an “average” pet home.

Overall foster homes are more likely to be closer to a shelter environment than they are to a “regular” home. Because of the nature of how most of us live, foster homes are at significant risk of environmental contamination. At the same time, we often place our most vulnerable animals into foster care: the very young, those recovering from injury or illness, or animals who are highly stressed, just to name a few.

We generally recommend considering foster homes to be similar to shelter environments and vaccinating them accordingly. This would mean starting vaccinations at four weeks of age and continuing every two weeks up to 20 weeks or for as long as the animals remain in the foster home or the shelter’s care. This frequency can sometimes be increased to every 3-4 weeks for kittens in a low risk foster home setting. Low risk would include foster homes where sanitation and infection control protocols are properly followed, only one animal or litter is fostered at a time, and there is no significant concern about exposure to infectious disease from any previous foster animals."

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