Herd Immunity et. all
This video from HealthCare Triage explains Herd Immunity very effectively and uses the example of Varicella (chicken box) after the introduction of the vaccine in 1995. Herd immunity was shown to be so effective that between 2004 and 2007 there were no deaths for children under 1 year old related to Chickenpox (the vaccine is only given to children older than 1). If that doesn't show effectiveness. I don't know what to tell you. (source: https://www.ncbi.nlm.nih.gov/pubmed/21788222 ) Measles has shown evidence of herd immunity. Out breaks for Measles only occur in populations and communities where vaccination is low. While no vaccine prevents infection in 100% of cases, the reduction of infection combined with high innoculation in the population has been shown to reduce instances of measles substantially, until 1989 when vaccination rates fell. Occurance of measles has continued to increase (in un-or-undervaccinated population). (source: https://www.annualreviews.org/doi/a...