It's not uncommon for babies to vomit

It's not rare uncommon for babies to vomit after breastfeeding. In most cases, it's not a sign of illness. Your baby's immature stomach differs in form from that of an adult. Also, because the sphincter at the stomach entrance is still undeveloped, your baby often vomits when he burps. Your baby may stop vomiting automatically within 12-18 months after birth.
To prevent your baby from vomiting, straddle hold the baby when you breastfeed or let him burp a few times during breastfeeding. When you lay the baby down, the upper body should be above the level of the lower body or the face should be turned sideways, so that the breastmilk that the baby vomits does not clog the airways.
However, if vomiting becomes more forceful, or your baby loses weight even though he seems to be drinking enough, consult doctors, midwives or consultants.