This is unusual. Go back to the NAN1 formula just to see if he still vomits and coughs. If he does then it is not the milk but he may have an infection or may be having a problem with reflux.If he is fine on the NAN1 then he may not be able to tolerate one of the ingredients in NAN2 and he would be best on NAN HA2 which is a low allergy formula.
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