Devils advocate: If these are people that work around sick people all the time, couldn't many of them have already contracted and defeated Covid before the vacc

Devils advocate: If these are people that work around sick people all the time, couldn't many of them have already contracted and defeated Covid before the vaccines were available? Doesn't that offer a decent level of immunity (something close to what the vaccine offers)? And don't those people already have a good understanding of how Covid affects them individually? It's hard to argue such people need vaccines or else they don't "believe in medical science".