- These are usually due to an inappropriate response to the adjuvant or a particular adjuvant-antigen combination.
- Mild skin reactions at the site of subcutaneous injection. Subcutaneous injection sometimes causes a mild local inflammatory response which may develop into a longer lasting granulomatous lesion. Such reactions generally cause the animal little discomfort, but in some breeds of cats may cause a change in colour of new hair growth. For this reason it may be advisable to use an injection site in such cats where any change in hair colour will be less obvious than the scruff (for example on the chest where hidden by forelimb).
- Sarcoma formation at the site of subcutaneous injection. Sarcoma formation at the site of injection has been associated with some vaccines using aluminium-based adjuvants in cats. In one survey, most were fibrosarcomas malignant fibrous histiocytomas, although some osteosarcomas, rhabdomyosarcomas and chondrosarcomas were also reported. The authors of the survey suggested that rabies vaccines might be particularly implicated.
- Generalised mild reactions. Occasionally transient depression and pyre may be seen after vaccination, the underlying mechanism for which is unclear
- Generalised hypersensitivity reactions
- Acute anaphylactic reactions can occur with the use of any vaccine, but are particularly associated with the use of killed adjuvanted vaccines. In both cats and dogs, the signs are of vomiting and diarrhoea within minutes or hours of vaccination and severe respiratory distress (dyspnoea and cyanosis). Adrenaline or corticosteroids should be given promptly.
- Autoimmune anaemias occurring within a few weeks of vaccination have also been reported in both cats and dogs.
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