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Care for Your Pet After Vaccination

Perhaps no other medical advancement has saved more lives than vaccination. Modern vaccines are extremely effective and safe. However, it is common for many pets to experience mild side effects following vaccination, similar to those that humans experience. Rarely does a pet need veterinary medical attention for these normal minor side effects.

What are some common side effects of vaccination?

Some of the most common mild side effects seen after immunization include:

• Redness, mild swelling, and tenderness at the vaccination site
• Decreased activity levels (fatigue)
• Loss of appetite
• Low-grade fever
• Nasal discharge, sneezing, coughing, or other respiratory symptoms, which may occur up to 2 to 4 days after an intranasal vaccine (vaccination with drops or sprays via the nostrils) is administered

If any of these signs lasts more than 24 hours or if your pet appears extremely uncomfortable, notify your veterinarian.

"If any of these minor side effects lasts more than 24 hours or if your pet appears extremely uncomfortable, notify your veterinarian."

It is also common for a pet to develop a small, firm nodule at the vaccination site. It should begin to shrink and vanish within 14 days. If the swelling lasts longer than 3 weeks or appears to get larger or more painful, contact your veterinarian for instructions.

Are there other possible side effects of vaccination that I should watch for in my pet?

Other less common but more serious side effects can occur within minutes to hours after vaccination. These reactions are considered medical emergencies, and you should seek veterinary care immediately if any of these symptoms occurs:

• Collapse or fainting
• Difficulty breathing
• Persistent and severe coughing
• Small, red, raised, itchy bumps over the body (hives)
• Swollen or puffy eyes, muzzle, or face
• Persistent vomiting or diarrhea

"Before immunization, tell your veterinarian if your pet has had any previous vaccine reactions, regardless of how insignificant they may seem."

Before immunization, tell your veterinarian if your pet has had any previous vaccine reactions, regardless of how insignificant they may seem. If you have any concerns that your pet may have a serious vaccine reaction, wait at your veterinary clinic for 30 to 60 minutes after vaccination.

What is my takeaway message?

The vast majority of the tens of millions of pets are vaccinated without any problems each year. Closely monitor your pet, and report any problems to your veterinarian as soon as possible. Vaccines save countless lives and prevent devastating infectious diseases from threatening our pet loved ones. If you have any questions or concerns, please discuss them with your veterinarian.

© Copyright 2025 LifeLearn Inc. Used and/or modified with permission under license. This content written by LifeLearn Animal Health (LifeLearn Inc.) is licensed to this practice for the personal use of our clients. Any copying, printing or further distribution is prohibited without the express written consent of LifeLearn. This content does not contain all available information for any referenced medications and has not been reviewed by the FDA Center for Veterinary Medicine, or Health Canada Veterinary Drugs Directorate. This content may help answer commonly asked questions, but is not a substitute for medical advice, or a proper consultation and/or clinical examination of your pet by a veterinarian. Please contact your veterinarian if you have any questions or concerns about your pet’s health. Last updated on Jul 8, 2016.