Baby not feeding

[1987JEN]

Hi all, my DS had his 8 week jabs on Wednesday morning, he took them fairly well with minimal crying. However his appetite has dropped severely. It's now Saturday night and everywhere I've checked says it should only last 24 to 48 hours. He used to have 150ml of milk 6 to 8 times a day, now he has about 5 feeds a day and he'll have about 60ml before spitting out the bottle. He's slept an awful lot today, I'm thinking it's because he has no calories for energy. At what point should I start to be concerned?

Did he have the rotavirus oral vaccine? My LO had no appetite for about 5 both times with that one. He was very sleepy too especially with the first jabs for about 4 days. He’s had 3 lots of vaccines now and I found the Meningitis ones made him sleepy but the rotavirus really threw off his eating both times. I think I offered tiny feeds hourly during the day, 2oz was the max he would take I can remember it being frustrating. He was absolutely fine though and back to normal completely by about day 6. I called the health visitor on day 4 I think and they weren’t too worried, could you give the HV a call in the morning if his appetite is still down?

Ive had the same issue, one of my twins was completely fine after rotavirus vaccine whereas the other is barely eating and had had stomach cramps. He's 13 weeks now (9 adjusted) and is usually on around 23oz per day and had had an average of 13 over the last 2 days since he had it. How long should I allow this to continue before contacting doctor?