marrow. reporter: diagnosed with the incurrable blood cancer, multiple myeloma, he went into remission after a clinical trial 19 months ago, and then covid hit. if you were to get covid, god forbid, what would that mean for you? well, it could kill me. reporter: harrison is triple vaccinated. there are seven million immunocompromised people in the united states, but for people with multiple myeloma, the immune system could have a veloh limited protection. i haven t eaten in a restaurant for two years. reporter: colin powell s death from multiple myeloma and covid really hit home for harrison. it didn t make me more fearful. it made me more excited about doing what i can with however much time i have left. reporter: harrison says vaccines and masks are his best defense to stay alive and wishes they were less controversial. i d ask for people to keep their eyes open and their minds open, and wonder about their neighbors and family members