Ultimately unvaccinated people put the whole community at risk by reducing herd immunity. For pertussis the threshold is over 90% for prevention assuming that 1

Ultimately unvaccinated people put the whole community at risk by reducing herd immunity. For pertussis the threshold is over 90% for prevention assuming that 100% of the population is immunized. If 10% are not immunized then your already behind for a disease with high transmission rates.