While vaccines are essential for preventing serious diseases, adverse reactions occur in a minority of dogs and require prompt recognition and management to protect welfare.
Vaccine adverse reactions, while rare, cause acute welfare impacts ranging from mild discomfort from injection site reactions to life-threatening anaphylaxis. Anaphylaxis causes severe cardiovascular collapse, airway compromise, and extreme distress within minutes of vaccination. Prompt recognition and epinephrine administration are life-saving. Non-anaphylactic reactions including facial swelling and vomiting cause significant acute discomfort. The welfare management of adverse reactions requires both prompt treatment and modification of future vaccination protocols to reduce recurrence risk. Dogs with adverse reaction histories require individualized vaccination approaches balancing protection against disease with risk of reaction. The strong benefit-to-risk ratio of vaccination for most dogs means that adverse reactions should lead to protocol modification rather than vaccine avoidance.