Anecdote: a family member of mine is very COVID cautious and still hasn't had it due to long-term isolation. When he started seeing people a bit, so long as the

Anecdote: a family member of mine is very COVID cautious and still hasn't had it due to long-term isolation. When he started seeing people a bit, so long as they had tested negative recently, he got sick from someone in my family who had a mild cold. It completely knocked him out, and he said it was one of the top 3 illnesses he could remember (he's a senior citizen). I wondered if the impact it had on him was due to the fact that he hadn't been exposed to anything (no groceries, no offices, no malls) in 3 years.