(Defined as clinical disease which appears within a week or so of vaccination.)
Clinical signs commonly reported as vaccine reactions include upper respiratory and ocular signs, mouth ulceration, and in many cases also, lameness and fever. Typically such reactions occur approximately 6-7 days after vaccination, often after primary vaccination of young kittens, and it has been suggested that this syndrome may be associated with the FCV component of particular vaccines. Whilst some of the isolates appear to be similar to vaccine virus, many of them appear to be field viruses.
- Cat already incubating the disease - vaccination programmes are usually implemented when kittens are highly susceptible to infection because of waning maternally derived antibody. Carriers are widespread and ensure that there is plenty of field virus around.
- Cat may already be a field virus carrier, and may show recurrent or persistent related to damage from the original infection. For FHV too, the mild stress and disruption of routine during vaccination may stimulate an episode of
- Shedding in some carriers.
- Vaccine virus given by wrong route, i.e. attenuated live systemic vaccine inadvertently given by oronasal route as a result of aerosol from a syringe, or a cat licking the injection site of itself or others. In some cases even where the vaccine has been given correctly, vaccine virus may generalise and reach the oropharynx.
- Intranasal vaccination quite often results in mild sneezing and occasional cases of ocular or nasal discharges and oral ulceration.
- Individual animals may be immunologically compromised through intercurrent disease (e.g. FeLV, FIV, feline panleucopenia), or have particularly opportunist secondary microbial flora.
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