Can a dog over 2 yrs old get distemper in spite of vaccine?

I just want to know if it's possible for an adult dog who has followed a rigurous vaccination ´programme still be exposed to getting the diease.

its very rare but possible . i have only seen it happen once .

No vaccination is 100%. That is why it is so important for all dogs to be vaccinated, so that in a rare case where the vaccine doesn't take, there is no one else who can catch it/pass it on. Proper hygiene should be used around any dog with a known infectious disease. If you are concerned, your vet can do a blood titer level for most diseases vaccinated against in order to check that there are actual antibodies against that disease being produced by your dog's immune system. If a dog got their vaccines when their immune system was suppressed (i.e. while very sick) it is possible that their immune system did not activate to recognize the vaccine and cause immunity, similarly, if a dog has a depressed immune system then the immunity given by vaccination cannot operate properly and they may catch a disease that they would normally be immune to.