Can't help with the shivers, but when my son was switched from Pediasure to Resource for Kids 1.5 he would vomit profusely very morning - tons of vomit came out and it was a projectile vomiting type thing. Not a fun time for either one of us. We ended up going back to the Pediasure and the vomiting stopped immediately. The Resource has almost twice the amount of fat as Pediasure so I think that is where it's getting the extra calories from and he just couldn't handle that much fat.