Risks of Vaccine-Preventable Diseases
May 7, 2009
Saad B. Omer, M.B., B.S., Ph.D., M.P.H., Daniel A. Salmon, Ph.D., M.P.H., Walter A. Orenstein, M.D., M. Patricia deHart, Sc.D., and Neal Halsey, M.D.
Vaccines are among the most effective tools available for preventing infectious diseases and their complications and sequelae. High immunization coverage has resulted in drastic declines in vaccine-preventable diseases, particularly in many high- and middle-income countries. A reduction in the incidence of a vaccine-preventable disease often leads to the public perception that the severity of the disease and susceptibility to it have decreased.1 At the same time, public concern about real or perceived adverse events associated with vaccines has increased. This heightened level of concern often results in an increase in the number of people refusing vaccines.1,2
In the United States, policy interventions, such as immunization requirements for school entry, have contributed to high vaccine coverage and record or near-record lows in the levels of vaccine-preventable diseases. Herd immunity, induced by high vaccination rates, has played an important role in greatly reducing or eliminating continual endemic transmission of a number of diseases, thereby benefiting the community overall in addition to the individual vaccinated person.
Recent parental concerns about perceived vaccine safety issues, such as a purported association between vaccines and autism, though not supported by a credible body of scientific evidence,3,4,5,6,7,8 have led increasing numbers of parents to refuse or delay vaccination for their children.9,10 The primary measure of vaccine refusal in the United States is the proportion of children who are exempted from school immunization requirements for nonmedical reasons. There has been an increase in state-level rates of nonmedical exemptions from immunization requirements.11 In this article, we review the evidentiary basis for school immunization requirements, explore the determinants of vaccine refusal, and discuss the individual and community risks of vaccine-preventable diseases associated with vaccine refusal.