I am no expert but I think it’s important to remember we are all somewhat different. Some have weaker immune systems than others. Some notice the fuck flue, others don’t. I found out I was HIV+ when I was hospitalized with shingles. My bf at the time never felt any reaction; he tested positive after I found out. If someone has issues that strain the body (medical, drugs, or whatever) might be more likely to increase the severity and reaction.
as for the bonding question, only you can answer that.