apart from the medical/reaction viewpoint, there is a case to be made for catching certain diseases 'wild', rather than vaccinating against them.
in some instances, it would appear that vaccinating is pushing diseases into ageing populations (where the vaccine has worn off), and those diseases (chicken pox, mumps to name but a couple) are more serious, and have higher complication rates among adults than among children.
bear in mind that the mmr, when it was brought in, was a 'one jab for life' vaccine. which was found not to be as effective as originally stated, and so the booster was brought in, to 'mop up' those who did not gain immunity fromt he first jab.
it is now being discussed whether a further booster should be added, and indeed there are some doctors who believe it shoudl be 'topped up' every 4-8 years. a far cry from 'one jab for life'.
meanwhile, assuming that the boosters are needed - that leaves a lot of peopel wandering around thinking they are immune when in fact they probably aren;t, hence the risk to the ageing population.