L.S.
Yes, it is their shots. Your babies have been introduced to a foreign matter which is designed to push their bodies to be able to recognize it if it ever comes around again. Immunizations can make you ill and some more than others. This is why you should NEVER let your baby get shots while their immune system has been compromised. Also, after shots, do not put them in a situation where their fragile immune systems can be further taxed. Feed them well, no sugar or juices. Let them get plenty of rest, no traveling or changes of schedules. Also, if your baby does get sick, you must notify your doctor and the doctors must make note of this on your babies chart. Check the Center for Disease Control (CDC)and see if your doctor should make them aware as well. Take care of your children and remember that you are the Momma, you know your babies best!
Good Luck!