4 month vaccines

My son had his 4 month vaccines on Friday. Today (Monday ) was his third day of mild lethargy and he has no appetite. He was taking in about 35 ounces a day (eating 5oz every 3 hours except at night) and the whole weekend he barely ate. What he did eat all weekend, he spit up, which I would attribute to his reflux, normally but he spit up nonstop this weekend. He held almost nothing down. Today he showed only a little more interest and he ate 20 ounces. Spit up is less today. He's slept a lot. No fever. Seems mostly happy when he's awake. 
I called the nurses line and I was told it's probably the vaccines. How long does it take for them to feel better? She said if it's not better by day 5 to call back. But that seems like an awfully long time for him to go without eating enough. 
Any similar experiences?