One person's child getting sick because they didn't have the vaccination will cause many others who did vaccinate to also get sick

This isn't correct. Maybe you meant this:

One person's child getting sick because they didn't have the vaccination will cause many others who didn't vaccinate to also get sick

Models behind the threshold at which herd immunity is acquired are bogus: they don't take into account the social structure of the contacts and treat us exactly like a herd put altogether into the same space — which is of course false. This means simply that the threshold to herd immunity is in fact lower. Nonetheless there's a lot of buzz about it and the “fake” threshold is used as reference to set the standard for vax-campaigns — and of course to say that if it isn't sufficiently high, the culprits are the antivaxers.

As I see it now, the problem is as usual that the number of people who don't accept impositions they have the right to doubt about, oscillates… There are periods with more flocks and periods with more wolves. The human kind won't be eradicated by none of those — virii and bacteria included! Sometimes I believe that the solution to a problem (epidemics) is damaging the human kind. Biological evolution doesn't count victims: it happens in the right direction, or it doesn't happen at all. 25% could have been the price for natural selection and biological evolution. Nowadays humans trust technological and scientific evolution more.