Even if your puppy received an initial round, theyre not done getting vaccinations. Little puppies have immature immune systems, which makes them susceptible to infectious disease. Their mothers milk provides some protection to start, but after they part ways with their mother, youll need to begin a series of at least three vaccinations. These are typically spaced three to four weeks apart, beginning when your puppy is 6 to 8 weeks old (though there are a few exceptions).