4000 people out of the ~210M people in the US with at least one shot is 0.002%. You have a greater chance of both contracting and dying of COVID. Hell, I think you have a greater chance of drowning in your bathtub.

Ok, though, let's talk about people who already had COVID. Did they actually have COVID, as in, did they test positive, or did they just feel really sick and think they had it? Have they had recent antibody tests? Did those tests show that they have antibody levels that would give them protection (including against delta) comparable to a vaccine? Have they consulted a medical professional about this? If it's "yes" to those questions, great, probably no need to get vaccinated. I have no problem with that. But the "I got sick so I'm immmune" stuff I hear constantly sounds more like a hope than something the people who say it have actually researched and been tested for.