Eh, ini common lah lepas vaccination, some babies jadi a bit quieter or fussier for a few days sebab their body adapting to the jab, it's a normal response. Tapi kalau dia dah balik ceria dalam 2-3 hari dan makan/tidur okay je, tak perlu risau; ramai kawan saya cakap anak dia macam tu jugak lepas 5-month jab tapi terus sihat. Kalau dah more than 3 hari still quiet, susah nak makan, or any other change in behaviour, better check with your pediatrician just to be safe ya, dokter can reassure you it's just post-vaccination reaction or kalau ada apa-apa lain