Vaccines can lessen the severity of future diseases and certain vaccines can prevent infection altogether, and today, a variety of vaccines are available for use by veterinarians. Any treatment carries some risk, but these risks should be weighed against the benefits of protecting your pet from potentially fatal diseases. An uncommon but serious adverse reaction that can occur with injection sites, including those sites where vaccines are administered, is tumor growth (sarcomas), which can develop weeks, months, or even years after a vaccination.
Although the risk of feline injection-site sarcomas (FISS) is small, progress has been made over the years to help reduce that risk even further. There are some helpful resources, such as the American Association of Feline Practitioners’ Guidelines, that reflect recommendations on vaccinating cats in consideration of the cat’s specific needs, local epidemiologic factors, and in line with manufacturer directions. And today, veterinarians and owners alike expect vaccine labels to reflect accurate revaccination needs. Much of what is commonplace today was recommended by a Task Force that studied this issue and produced a report in 2001:
Vaccine side effects commonly happen and can
develop within hours of vaccination. Milder side effects include: local swelling
and discomfort at vaccination site, mild fever, lethargy and decreased
appetite. (See a related AVMA resource, Vaccinations: What to expect after your pet’s
More serious (and less common) side effects
include persistent vomiting and diarrhea, itchy and bumpy skin (“hives”),
facial swelling, severe difficulty breathing, and collapse. These reactions can
be life-threatening and are medical emergencies. Contact your veterinarian
immediately if any of these signs develop.
A small, firm swelling may also develop under the
skin at the site of a recent vaccination; this should disappear within a couple
weeks. If the swelling persists for more than three weeks, or if it appears to
grow larger in size, contact your veterinarian.