That is an essential concept. Consider the Salk polio vaccine: before the results of the conclusive trials were announced, it was speculated that if the vaccine was 25% effective, everyone would want to have their kids vaccinated. The results came back at around 85%, and the acceptance of the vaccine was high and, because of herd immunity, it reduced the incidence of polio by approximately 99.9%. Further techniques, such as switching back and forth between live virus and dead virus vaccines at multi-year intervals, boosted the effectiveness to observationally 100% when compliance was very high.