The anti-vaccination movement (also called the anti-vaxxer movement) is the modern phenomenon of distrust in vaccination. Anti-vaccination proponents blame vaccines or their ingredients for a range of maladies (often childhood illnesses and autism) whose mechanisms are not currently fully understood. The ubiquity of vaccination often makes it an easy target for blame.
Vaccine-preventable disease has been a major cause of illness, death, and disability throughout human history. The advent of the modern vaccine era has changed this significantly. In fact, most North Americans and Europeans have little memory of the pre-vaccine era, when diseases such as mumps and measles (to say nothing of polio and smallpox) were very common. In more recent times, there has been much debate regarding vaccine safety; namely what possible side-effects vaccines might cause and whether these outweigh the risks of leaving a population without a vaccination program. Vaccines have been alleged to cause all manner of illnesses; autism is a prominent example, as its direct causes are still fairly mysterious and probably very wide-ranging, with no single cause or lifestyle risk-factor being identified. Some very prominent Americans have spoken out vociferously about the supposed danger of vaccines.