Chances are people with 4 doses are old as fuck or immunocompromised.
Not where i live
Vaccines, Boosters, and Masks are the sign of a good Democrat...I wish I was kidding.
Not sure of the numbers here but those who got initial two shots have kept up with boosters regardless of age or health...our local/state news cycle pumps the fear mongering every month or so pretty hard and that gets results IMO.
Sidenote: I know probably a dozen people who have gotten side effects right after their 3rd, 4th booster in the last 6 months. Most of them are mostly in denial about it and consider it a coincidence.
Yesterday I spoke with a family friend and he has had bad vertigo for 2 months, can't figure out why, his doctor is blaming long covid. I said that is a potential side effect of mRNA vax...he didn't like that possibility. He had covid over a year ago and the Vertigo arrived 4 days after a Booster.