On the one end there is a possibility of all the diseases to come back
This would be diseases like smallpox, polio, whooping cough, tuberculosis, measles, etc., that used to kill millions, that universal vaccinations have saved millions and millions of lives.
You agree about that, correct?
but on the other hand your are opening them up to a host of other diseases.
Do the vaccinations kill millions? If not, isn’t it better to save millions of lives with universal vaccinations than to save much less lives without universal vaccinations?