Are unvaccinated people actually healthier?

One refrain you often hear from anti-vaxxers is “follow the money.” So we did, and we found that this study was funded by two different anti-vaccine organizations (Generation Rescue, Inc., and the Children’s Medical Safety Research Institute). The study, which was retracted a month after it was published, relied on surveys sent out to parents of homeschooled children. They didn’t specify how many people were eligible to take the survey, but they only received 415 responses.

One concern about their methods is self-selection bias, or volunteer bias, in which participants can decide whether or not to participate in the study. Additionally, the home-schooling population is not representative of the general population, and some reasons to homeschool include a “desire to provide moral instruction” and “child has special needs” or other health problems.

Along with self-selection bias, a study design like this introduces other biases such as recall bias and reporting bias. The study itself shows that the unvaccinated group was less likely to seek medical or dental care and less likely to use medications. They might also have a different perception of illness or neurological disorders than someone from the vaccinated group.

A study this small with so many clear biases needs to be discarded (or retracted–which it was).