How long can vaccine side effects last?? Everything I’ve read says up to 48 hours but we are on day 5 after her 2 month shots and she is terribly fussy (normally a SUPER happy baby) and SO sleepy. Waking up basically just to eat all day and go back to sleep whereas she’d normally play for a while before another nap. Could this be from vaccines? Or could she be actually sick? She has no other symptoms and is 10, almost 11 weeks old if that matters