Alah, normal je lah, babies lepas vaksin memang boleh jadi perut a bit loose, especially if you're breastfeeding. A few of my mum friends noticed the same thing with their babies after injections, and one paediatrician told me it's because their body is reacting to the vaccine. Kalau baby alert, feeding well, and poop nya normal colour (yellow or greenish), you're probably fine lah, tapi if you're worried or if it lasts more than a few days, boleh je check with your doctor untuk peace of mind!