As cases of measles continue, the Centers for Disease Control and Prevention (CDC) and President Obama urge vaccination. However, Senator Rand Paul, a potential candidate in the 2016 U.S. presidential race, makes claims that vaccines cause “profound mental disorders” and advocates for optional vaccination.

Paul stated that he had heard of “many tragic cases of walking, talking, normal children who wound up with profound mental disorders after vaccination.” Paul also stated that vaccination should be subject to input from the parents. He insists that some of his comments were taken out of context and that he is not anti-vaccination, however his spokesperson confirmed that Paul believes many vaccines should be voluntary.

According to medical research, the effectiveness of vaccines does not come from simply an individual choice to be vaccinated, but because of a phenomenon known as herd immunity. Herd immunity protects individuals of a population by limiting how many people a pathogen can be exposed to, and limiting how many sources individuals are exposed from. One vaccinated person in a population of unvaccinated people will most likely become ill due to the immune system still becoming overwhelmed.

Despite Senator Paul being a former physician, the importance of vaccination and herd immunity is not influencing  his public policy opinions.

Governor Chris Christie, another presidential hopeful, also advocates parental choice in child vaccination. Although he gets his own children vaccinated, he holds the opinion that other parents should not be legally required to do so.

At the moment, all states require children to be vaccinated in order to enroll in school, however 20 states allow unvaccinated children in if they have a waiver. Some children are unable to be vaccinated due to legitimate medical concerns such as allergies, but more and more parents are acquiring waivers out of fear of adverse mental effects such as autism.

Claims that autism is linked to vaccination have been scientifically refuted, and in fact have their origin in a 1998 study which was discredited and shown to be fraudulent. Medical research, as well as the recent outbreak of measles demonstrates the importance of herd immunity in protecting vaccinated and unvaccinated children alike.

Until recently, measles was all but eradicated by vaccination. Cases of other diseases such as whooping cough, mumps, rubella and chicken pox are also becoming more frequent as vaccination numbers decrease.