Prior to the introduction of vaccination, people's immune systems had every opportunity to "strengthen". The chance of a newborn child surviving to adulthood was frequently less than 50%, and sometimes a lot less. People adopt the woo position out of sheer ignorance of history, combined with the mythology of a lost simple life, and they put at risk not only their own children (arguably child abuse?) but other people's too.

Be grateful for developments in public health- treated sewage, vaccination, pasteurisation and other hygiene measures, clean air, contraception, anaesthesis, good surgical practice, antibiotics and so on. The widespread and wilful ignorance of the benefits wrought by science, medicine and engineering is a feature of our selfish age, in which everyone is encouraged to think of themselves as an isolated, self- sufficient consumer.

No doubt someone will mention the atom bomb, as if it trumps everything.