I'd avoid the formula too like the others have said.
My gremlins got rotavirus at 13 mths and ended up with nearly a week in hospital, the advice we were given then was no formula or solid foods while there was vomiting, only clear fluids. The ratio they use in hospital is 5ml per minute via syringe of either pedialyte or water depending on what they'll tolerate. The aim is to replace the amounts lost. If they'll take it from a bottle or cup then all good, if not then you pretty much have to hold them down and syringe it in
After the vomiting stops (at least 6 hours, preferably 12) try reintroducing some plain solids (such as the pear you mentioned). Once bub is tolerating that OK you can offer formula again.
A small percentage of babies develop temporary lactose intolerance after a tummy bug in which case soy would be a good choice until that resolves, but I'd check with your doc before trying that, and not until the vomiting has stopped.
Hope this helps, v and d bugs are awful!