I think I slept for 18 hours the first time I was given vedolizumab. I thought it was just me so I'm glad to know it happens to others too!
It did get better though. I'm now on my...*thinking*...7th? 8th? infusion- I still am tired and "off" for the rest of the day after the infusion, and I am slightly light-headed for a bit after, but I don't have to sleep all day and night to make it feel better either.