First vaccines done and now sleepy and not feeding

Hi

my little boy had his first vaccines today at 2:20pm he is 14 weeks old so rather late having them. He cried whilst having them but I calmed him quickly and gave him some calpol and then he had his nap. When he woke up 1 hour later he ate a big feed and seemed his normal self all happy. he then started to get grumpy I tried to give him his next feed but he wasn't interested and he went back to sleep instead. He has been crying each time he wakes up which isn't like him but he quickly falls back to sleep refusing to feed in the few minutes he wakes for. My husband managed to get a smile out of him whilst he was drowsy but then he went straight back to sleep I gave him his 2nd dose of calpol after 5 hours it's now 6 1/2 hours since his last feed and he's still sleeping he normally sleeps through the night until 4am. I don't no what to do? Let him sleep it off, try and wake him for a feed shortly but I don't think he's going to be interested again or ring NHS direct for advice i would appreciate your opinions basically he is sleepy and not feeding since vaccines.

thanks