Beth got her foster kitten "Frito" vaccinated for the first time TODAY and is allowing him to mingle with the other cats because she apparently thinks the vaccines become effective immediately. NOT TRUE !!!! What an idiot! bethostern The moment Frito has been waiting for! He had his very first set of vaccinations today and now able to be around other kitties! He's smelled them from under the door for 2 weeks and is familiar with them through their scents. That's how I suggest all older kittens and adult cats are introduced to other kitties. It works for harmony. #happyfrito 2h From the Animal Health Services website: How many vaccines does my puppy or kitten really need? In order to provide optimum immunity, puppies and kittens should be vaccinated every 3-4 weeks until they reach the age of at least 20 weeks. The best ages to vaccinate are 8, 11, 14, 17, and 20 weeks of age. How long does it take for these vaccines to take effect? Generally the vaccines take a 2-7 days to take full effect. If the pet is to be boarded or exposed to other pets, the vaccines should be administered at least one week prior.