With vaccination commonly recommended annually, most pet owners are accustomed to taking their pets to the vet for "yearly shots."  It seems such a commonplace part of routine pet care that many people do not think about what is actually occurring within their pet's body.  In fact, immunization represents stimulation of the immune system, an inherently inflammatory process. It is typical for some joint or muscle soreness to occur after vaccination, for lethargy to be observed, or for a mild fever to be present for a day or two.  These reactions are not serious and generally go unnoticed.  Pets may eat, drink, and exercise normally after vaccination if they want to; it is the more serious allergic

Pepper’s facial swelling is actually from an insect bite, but would look identical to the facial swelling of a vaccination reaction

reactions that need to be distinguished from the above expected phenomena

ALLERGIC REACTIONS

Allergic reactions are highly individual inflammatory responses against specific proteins entering the body.  These proteins can be pollens, dusts, foods, medications, or even vaccines.

An allergic reaction might include hives, facial swelling, or even nausea. More serious reactions can include shock  or sudden death ("anaphylaxis").

The time frame after vaccination can be immediate (the "Type I" reaction) or anytime in the next 48 hours (the "Type IV" or "Delayed Hypersensitivity" reaction.)

WHAT TO DO DURING THE REACTION

If your pet is having a reaction more severe than just some general malaise or soreness, you should let your veterinarian know right away. If it is after hours, it is prudent to consult the local emergency clinic.  Anti-inflammatory injections can be used to halt the inflammatory cascade before it gets dangerously out of hand. Be sure you know who to call in case of problems after your pet is vaccinated.

Vomiting may be a sign of an on-coming serious reaction,
or could represent something as mild as car sickness.
If vomiting is observed, let your veterinarian know right away.

WHAT TO DO IN THE FUTURE FOR THE PET WHO HAS HAD REACTIONS

There are many steps that can be taken to prevent allergic vaccine reactions:

• AVOID LEPTOSPIROSIS VACCINE
  The leptospirosis portion of the DHLPP (distemper) vaccine for dogs has a reputation for being the most likely portion to cause vaccine reactions. You can request that this portion be left out of your dog's vaccine.
   
• AVOID GIVING SEVERAL VACCINATIONS AT ONE TIME
  Keep in mind that vaccines given within two weeks of each other  can interfere with each other so you do not want to separate vaccines by less than a two week period but separating vaccine can mean your pet has less stimulation to deal with at one time. Breaking up vaccines also helps determine which vaccine is the culprit.
   
• DO NOT HAVE YOUR PET VACCINATED AT A VACCINE CLINIC
  Vaccination clinics are designed to provide streamlined service for healthy pets in need of their regular immunizations. These clinics are generally not prepared for the individual attention required by a pet who has a history of vaccination reaction.  A pet with a vaccine reaction history should receive some special attention in the form of observation in the hospital and/or pre-treatment with anti-inflammatory medication.
   
• BE SURE YOUR VETERINARIAN IS AWARE OF YOUR PET'S HISTORY OF VACCINE REACTION
  This sounds very obvious but I have seen many people at vaccination clinics wait until after the animal has been vaccinated before informing the veterinarian that the pet has a history of reactions.
   
• BE PREPARED TO PAY FOR EXTRA PRE-MEDICATIONS AND/OR OBSERVATION IN THE HOSPITAL
  Medications can be used to "head off" allergic reactions before they happen and with the use of these medications it is possible that a reacting pet can be vaccinated normally. To be safe, it is frequently recommended that the pet be observed for the day after vaccination, despite the medication.  Consult your veterinarian regarding his/her recommendation.

Vaccination reactions severe enough to produce shock are EXTREMELY rare and are a function of an individual pet's immune response. Vaccination is an important part of responsible pet ownership and should not be omitted without specific veterinary guidance.