My 4 month has 100.4 fever after vaccination, fever was not there before 12 hours, is it ok?

Yes. If your baby is: Uncomfortable, give tylenol (acetaminophen) in the dose your pediatrician recommends. Maternal metabolic disorders ( obesity, hypertension, diabetes) are associated with ? risk of autistic spectrum disorder & other neurodevelopmental disorders, fever from vaccines is not. The aap recommends developmental surveillance with standardized screens (on firstsigns.Org & the aap's healthy child app) for all children.