Hello I am Dr. Joey. Thanks for trusting me to help you and your pet today. I am a licensed veterinarian with over 15 years of experience. I look forward to working with you.
Based on what you report this does sound quite concerning for your dog. This could be an atypical vaccine reaction that is leading to delayed lethargy and persistent nasal irritation (I assume that she received the intranasal vaccination). Usually irritation from the intranasal vaccination to caused increased level of reverse sneezing/snorting lasts a few hours and then disappears but could persist up to 12-24 hours. It is highly unusual to see a reaction to this vaccination. However, I do recommend phone your vet today to alert him/her of this issue. If she was my patient I would advocate treatment with diphenhydramine to counteract allergic reaction (at a dose of 1 mg per pound every 12 hours)
If she is worsening with her level of lethargy and/or develops any digestive tract issues (vomit, diarrhea, not eating) then she needs to be reexamined today and potentially administered a corticosteroid injection to help counteract vaccine reaction. However, this may not be a vaccine reaction and instead there is something else going on.
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