I would say at best this is currently unclear, so no it is'nt "99% safe" (depending on your definition of safe) because: 1. It's possible the strains could mut

I would say at best this is currently unclear, so no it is'nt "99% safe" (depending on your definition of safe) because: 1. It's possible the strains could mutate so they are different enough for the immune system to not respond (assuming you build immunity). 2. As far as i know the scientific community has not established exactly what the situation is with immunity. There are reports of reinfection. This could also possibly be due to testing issues. 3. Right now it's not obvious how long you are contagious for.