Vaccine Controversies - Safety

Safety

Few deny the vast improvements vaccination has made to public health; a more common concern is their safety. All vaccines may cause side effects, and immunization safety is a real concern. Unlike most other medical interventions, vaccines are given to healthy people, and people are far less willing to tolerate vaccines' adverse effects than adverse effects of other treatments. As the success of immunization programs increases and the incidence of disease decreases, public attention shifts away from the risks of disease to the risk of vaccination, and it becomes challenging for health authorities to preserve public support for vaccination programs.

Concerns about immunization safety often follow a pattern. First, some investigators suggest that a medical condition of increasing prevalence or unknown cause is an adverse effect of vaccination. The initial study, and subsequent studies by the same group, have inadequate methodology, typically a poorly controlled or uncontrolled case series. A premature announcement is made of the alleged adverse effect, resonating with individuals suffering the condition, and underestimating the potential harm to those whom the vaccine could protect. The initial study is not reproduced by other groups. Finally, it takes several years to regain public confidence in the vaccine. Adverse effects ascribed to vaccines typically have an unknown origin, an increasing incidence, some biological plausibility, occurrences close to the time of vaccination, and dreaded outcomes.

Controversies in this area revolve around the question of whether the risks of perceived adverse events following immunization outweigh the benefits of preventing adverse effects of common diseases. There is scientific evidence that in rare cases immunizations can cause adverse events, such as oral polio vaccine causing paralysis. Current scientific evidence does not support the hypothesis of causation for more-common disorders such as autism.