My son started throwing up at half past 2 and threw up again just 15 minutes ago. should i be concerned that this could mayb be listeriose?

He is very young: Take him to the doctor for exam children can dehydrate very quickly so get him checked. Then you will have a diagnosis

Vomiting is: common with mild illness, especially with viral gastroenteritis, but Listeriosis is not common in children this age unless immune compromised and is usually associated with fever and chills. Continue to offer clear liquids, in spite of vomiting, every hour or so. If vomiting persists for more than 12 hours, urine output is decreased, color looks pale or alertness is decreased, he should be seen