Medical reasons for exemption from vaccination may include history of anaphylaxis to a vaccine component or immunodeficiency in the case of a live vaccine.
Reasons why a parent may refuse a vaccine for a nonmedical reason:
(1) The vaccine is not safe.
(2) The vaccine is not efficacious or is not beneficial.
(3) Belief that too many vaccinations may weaken the immune system.
(4) Belief that the infection is not a threat.
(5) Religious beliefs (this may be a false positive in some states since claiming religious belief is the only way a vaccine can be declined.)
(6) Distrust of the government, organized medicine or science.
(7) Confidence in alternative medicine, pseudoscience or unorthodox practices.
(8) Belief in freedom of choice (and not liking being told what to do).
(9) Belief that experiencing an infection is somehow more natural.
(10) Belief that healthy children do not need vaccination.
Parents may refuse some but not all vaccines. For example, varicella was refused at almost 3 times the rate of polio vaccine.
Additional factors not listed that may contribute to the parent's decision:
(1) never having experienced an epidemic
(2) transference of fears or anxiety to vaccines or vaccine components
(3) poor understanding of or misconception about science
