Just like children, new puppies and kittens need to be vaccinated against easily preventable viruses. Starting at 6-8 weeks, puppies and kittens should get regular boosters until they are 4-6 months old. While nursing (generally up until 8 weeks) puppies and kittens are protected by ‘passive’ antibodies in their mother’s milk as long as the mother is up-to-date on her vaccinations, as well. Vaccinating your pet is the most effective way to protect them against the viruses they could come in contact with. While some of the diseases, like Rabies and Hepatitis, must be transferred through bodily fluids, other diseases, like Bordetella, can be carried through the air and aerosols and transferred easily among animals at places like dog shows, kennels and parks. Many of these diseases are lethal – especially to puppies and kittens – and all of them are expensive to treat.