Vaccination has transformed the health and welfare of farmed salmon in Norway and other countries, dramatically reducing antibiotic use and disease-related mortality. Fish vaccination welfare involves the procedure itself as well as its benefits.
Fish vaccination represents a rare case where a single intervention dramatically improved welfare across an entire industry. The elimination of most bacterial disease through vaccination prevents far more suffering than the vaccination procedure itself causes. However, vaccine side effects including peritoneal adhesions in some formulations represent a welfare cost that should be minimised through vaccine development. The Norwegian example demonstrates that welfare-positive and commercially successful salmon farming are compatible when disease prevention is prioritised.