“My cat went into the cattery and come out with the ‘flu! He was vaccinated! What went wrong?”
We hear this comment every so often, and it certainly is frustrating for owners who have done everything they can to ensure their moggies stay healthy.
The main issue is that no vaccine, whether for humans or animals, is 100% protective. Vaccines are designed to reduce the incidence and severity of the disease, and apart from living in a hermetically sealed bunker, they are the best method we have to do this.
The other issue with cat flu particularly, is that many cats are carriers of herpesvirus or calicivirus, the viruses known to cause cat flu. Carrier cats will not show any clinical signs of flu until they become stressed – and going to a cattery is a classic example for those cats who prefer the comforts of home – the cage, the car ride, the room away from home with lots of new cats around.
So if your cat comes back from the cattery with ‘flu, it’s unlikely that it’s due to a vaccine failure: either the vaccine has provided as much protection as possible, or your cat may be a carrier of herpes or calicivirus.
Different vaccinations will have different levels of efficacy. For example vaccinations against panleukopaenia (a virus which causes vomiting, diarrhoea and immune suppression) can reach 98% efficacy. However vaccinations against herpes and calicivirus may only attain 70% efficacy. This has a lot to do with the nature of the virus in question. Another example is the feline immunodeficiency virus (FIV) vaccine that has an 80% efficacy.
So is it still worth vaccinating? Absolutely! If there is a 7 in 10 chance that your pet could be protected from a potentially debilitating disease, you would take those odds, right? And pets that are vaccinated are likely to have a milder form of the disease if they do get sick.