My cat is not eating and lethargic after vaccine. Is it a reaction?
Updated On September 23rd, 2025
Pet's info: Cat | Mixed Breed | Male | 1 year and 5 months old | 5 lbs
Hi there, my cat Jasper just got his final round of conjunctivitis vaccine last night. Afterward he didn't eat really and wasn't playful like usual. Which I figured was fine because he was probably nervous about the vet. But this morning he's still not eating and looks lethargic. This cat is always hungry so I was wondering if it's common to have a bad reaction to the vaccine? Should I bring this up with my vet?
2 Answers
Most Helpful Answer
Published on March 16th, 2017
Poor Jasper! The timing of his signs certainly correlate with his vaccine. Not eating and lethargy (as well as vomiting, diarrhea, facial swelling and hives) can be signs of a vaccine reaction. Vaccine reactions are uncommon, but do happen. If Jasper still isn't eating by later today, I would give your vet a call to have him rechecked. Some vaccine reactions require steroids and/or antihistamines for treatment.
1Pet Parents found this answer helpful
Related Answers from Veterinarians
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Published on March 3rd, 2020
Hi there and thank you for using Petco Pet Education Center, formerly Petcoach to address your concern. If you think Jasper is acting strange and is having a possible reaction to the vaccination, I would take him back to the veterinarian so that the most appropriate diagnostic and treatment recommendations can be made. I hope this helps!
1Pet Parents found this answer helpful
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