The Difference Between Killed & Modified Live FVRCP

Cats require a range of vaccinations for protected from potentially life-threatening contagious diseases. The FVRCP is a recommended feline combination vaccine that guards against several diseases that are common in cats. The acronym stands for feline viral rhinotracheitis, calicivirus and panleukopenia, which are the three diseases that the vaccine helps to prevent. The FVRCP vaccine is available in killed and modified live versions, with important differences between the types.

  1. Definitions

    • Just as the name implies, killed vaccines contain killed versions of viruses. They create immune responses within the body without the possibility of the diseases occurring. Modified live vaccines contain actual live viruses that have been altered to cause mild forms of the diseases. This form of the FVRCP vaccine results in the production of antibodies that make the animal immune to the three feline contagious diseases.

    Considerations

    • The modified live version of the FVRCP vaccine offers the benefit of quick results, with an immune response occurring within 48 hours of the first vaccination. This is particularly important for pet owners with kittens or new cats that require a series of vaccinations and for those who often bring new, unvaccinated felines into their homes. The killed variety may require two shots within two weeks to generate any level of immunity. Because the modified live version creates mild forms of the diseases within the FVRCP, the protection it provides is fast and reliable. However, it also poses more risks than the killed version.

    Risk Factors

    • The FVRCP vaccine that contains killed viruses is safe to give to pregnant and lactating females and is also less dangerous to ill, fragile or senior cats. In addition, there is also no chance that it will cause cats that receive the vaccination to become ill with diseases. Though the modified live version usually only brings on mild incidences of the viruses, there is always a chance of more serious illness occurring. It also causes the viruses to be shed, which can induce disease in cats that have not been vaccinated. However, modified live FVRCP vaccines do not contain immune-boosting chemicals that the killed varieties must have to be effective. These chemicals can create certain side effects not common when the modified live version of the vaccine is administered.

    Side Effects

    • The chemicals used in the killed FVRCP vaccines are called adjuvants and are necessary to produce antibodies since the viruses are not live. These chemicals can result in irritation, pain and swelling at the site of injection. Rarely, serious reactions such as cancer or paralysis in the area where the shot was given may occur. Typically, the only side effects caused by the modified live version of the FVRCP are teary eyes, a slight cough and occasional sneezing.