The mortality rates from most infectious disease have actually been in steep decline even prior to the introduction of vaccination. The mortality rates from measles and pertussis for example have declined by almost 99% prior to the introduction of vaccination in developed countries such as the US.
It is the improved living conditions, clean water, better nutrition, better sanitary measures when it comes to sewage disposal etc. that seem to have played the major role and not vaccination.
We also know that natural acquired immunity is not the same as vaccine induced immunity. The much indorsed
"heard immunity" form vaccination, being a far cry from
"natural heard immunity", the later being much more protective, far long lasting, & is transferable from mother to child (offering protection in this vulnerable stage of development).
We already know that protection against pertussis waned over time. A study in the New England Journal of Medicine;
http://www.nejm.org/doi/pdf/10.1056/NEJMoa1200850, proved this when it concluded that
“protection against pertussis waned during the 5 years after the 5th dose of DTaP".
It is clear the pertussis vaccine becomes ineffective over an extremely short amount of time- likely due to pertussis bacterium developing resistance, similarly to bacteria becoming resistant to antibiotics.
Furthermore, recent studies found that immunised individuals when exposed to 'wild Bordetella pertussis bacteria' take longer to clear the diseases than those that have natural pertussis and thus also gain natural immunity. These vaccinated persons may then become asymptomatic carriers of the bacteria and vectors from transmission. This only supports the idea of
"heard immunity" from vaccination being a far cry from
"natural heard immunity"; with the latter being much more protective, long lasting as well as transferable between mother and child and thus better overall for the community in the long run.
These are all sufficient grounds against mandatory vaccinations.