July 2, 2019, Vol 322, No. 1, Pages 3-90
Outbreaks of Vaccine-Preventable Diseases – Responding to System Failure With National Vaccination Requirements
Matthew M. Davis, MD, MAPP; Seema K. Shah, JD
Outbreaks of vaccine-preventable diseases indicate failures in health care and public health systems. One type of failure occurs when a vaccine offers insufficient protection, for instance during an influenza season when the predominant circulating strain is unrelated to antigens included in the flu vaccine for that year. Another type of failure occurs when a safe and effective vaccine is available in wealthier nations, but is not accessible to eligible patients in less wealthy nations because it is prohibitively expensive. A third type of failure occurs when parents choose not to immunize their eligible children with recommended vaccines. This particular form of system failure puts each unvaccinated child at risk for vaccine-preventable illness, and also undermines herd immunity that otherwise protects children from the same illness. From a system perspective, herd immunity is a system redundancy that helps guard, but does not completely protect, against failure.