Vaccination protects companion animals from serious disease, but the ethics of vaccination schedules, titers versus revaccination, and over-vaccination are important welfare considerations for responsible ownership.
Vaccination welfare involves navigating between two genuine welfare risks: the harm of preventable infectious disease in under-vaccinated animals, and the harm of unnecessary vaccine reactions and immune stimulation in over-vaccinated animals. Historical annual revaccination schedules were established when duration-of-immunity data was limited; subsequent research demonstrating that many core vaccines confer immunity lasting 5-7 years or more has led to revised guidelines recommending less frequent boosters for established immunity. Titer testing provides an evidence-based alternative to reflexive revaccination: measuring antibody levels confirms whether protective immunity is present, allowing informed decisions about whether booster vaccination is needed. This approach respects the welfare evidence on both sides — maintaining protective immunity while avoiding unnecessary antigen exposure in animals with existing immunity. The practical barrier is cost, particularly for titer testing, and owner education about the changed understanding of vaccination duration. Vaccine reactions, while uncommon, cause acute welfare harm in affected animals, making minimization of unnecessary vaccines a genuine welfare objective rather than simply a philosophical preference.