In AmE pronunciation, the 't' in 'vital' is pronounced with what we know as a 'flap t', which sounds pretty much like an 'r'.
In BrE, however, the 't' in 'vital' would just be pronounced with a regular 't', which of course makes it totally different to the word 'viral', with a regular 'r'.
P.S. I'm talking about the general, 'standard' form of both varieties of English.