Yes, a dog that has been vaccinated for Distemper can still become infected with Distemper. No vaccine is every 100% effective. If a vaccinated dog becomes distemper positive, they will not necessarily have a shorter duration of the illness or experience less severe symptoms. Once a dog has become infected, it is impossible to predict how well they will or will not do, but intensive veterinary monitoring and hospitalization can be helpful. Please see the following website for more information on distemper.
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