My father-in-law had a bad habit. (He actually had several — don't we all? — but I'm going to talk about one in particular.)
For most of his life, when he got sick enough to go to a doctor, the doctor would give him medicine to treat it. Then he'd take the medicine as prescribed, but stop once he felt better even if the medicine wasn't done.
The problem with that is that just because the symptoms are gone doesn't mean that the disease is. So, of course, after he stopped taking the medicine the illness would come back, and this time it would be more resistant to the medicine because the germs that died were the weaker ones.
I fear that our society is in danger of a making very similar mistake with COVID-19. Restrictions are being relaxed or removed, and many areas are achieving the stated goal of 70% vaccination, so we're starting to let our guards down — particularly in the area of vaccination.
Different people have different reasons for not getting the vaccine, and some of them are quite legitimate. I'm specifically addressing the thinking of, "Since everyone else is vaccinated, I don't need to," though it can also apply to "I'm not getting it because it's my body and I choose not to."
Leaving "herd immunity" to others is irresponsible. It leaves yourself and those around you exposed to a deadly disease.