I don't think its necessary to v*. I got ill last year and my husband did within hours of me. I didn't v* even though i came close, but i did have d* around 10 hours after i started feeling ill. By this point i was feeling less n* though and just wiped out. My husband did v* a few times over about 5 hours after he started feeling ill. By the next day were both almost fine again just a bit tired and run down. I don't think it's harmful not to v*, but i suppose it may just prolong the n* in some cases.