It is not a matter of the puppy in a public setting as it is the nature of the bad viruses that your puppy is exposed to. Parvo virus is the most deadly virus especially for puppies. The transmission is from another dogs infected feces, so keep your puppy away from any other dog’s feces.  Kennel cough, or upper respiratory infections, are nose to nose transmitted infection and vaccinations are started at 8 weeks of age. The principal of vaccination is that puppies do not have a fully functioning immune system and their vaccines are not completely effective until their last vaccination at 4 months of age.  Consult with us regarding specific concerns or questions regarding vaccines and contagious infections.