Many vaccine critics suggest that by doing a large-scale vaccine study of vaccinated versus unvaccinated children, much of the controversy around vaccines would be settled; and that by not doing it, the federal government (read CDC) and vaccine advocates are trying to hide evidence that vaccines are dangerous. This is probably a question many vaccine-weary parents have asked as well.
Meanwhile, the typical response from vaccine advocates is simply that this would be an unethical study to do with no reason given for why. We want to explain why.
There are two research approaches that could be applied to this problem. Unfortunately, both have serious drawbacks.
1. A retrospective cohort vaccine study.
This would entail looking back at thousands of medical records of children that 1) completed the schedule of recommended vaccines on time, or 2) didn’t receive any vaccines. Children that a) received some but not all of the recommended vaccines, or b) used an alternative schedule, would also have to be accounted for but not included.
Another difficulty arises when making sure those two groups (vaccinated or unvaccinated) are alike in all other aspects; including socioeconomic background, medical background and, most importantly, health-seeking behavior.
Health-seeking behavior is a tricky element in any study. Why is that? Controlling for health-seeking behavior is difficult because those who don’t vaccinate may believe their children are healthier because of good nutrition or less exposure to toxins in the environment. This unvaccinated group may also be less likely to take their child to a physician, even if they suspect mild autism disorder, allergies or any other chronic condition, and instead try homeopathic treatments. Tracking medical records of people who self-prescribe alternative health options is very difficult to do, and so researchers are dependent on self-reporting, which leads to significant problems of bias in a study.
Finally, finding a large enough number of subjects to generate enough statistical power would be difficult. Although the number is rising, it is currently estimated that less than 1% of all US children have no vaccines at all. This number does not include children who have had one or a few vaccines, which is a much higher percentage.
German researchers did do a study with 13,463 children, of which 0.7% were completely unvaccinated (less than 100 children). They examined medical records and did parent interviews. The conclusions were that unvaccinated children were at greater risk for contracting vaccine-preventable diseases and “the prevalence of allergic diseases and non-specific infections in children and adolescents was not found to depend on vaccination status.”
2. A prospective cohort vaccine study or, better yet, a randomized double-blind study,
This would be the gold standard of scientific studies. This involves taking a very large group of children (tens of thousands) and giving some of the subjects vaccines and creating a control group with no vaccines. The subjects, parents, doctors and even some of the researchers would not know if the child had received an actual vaccine or a placebo. A very large number would be needed in order to look for chronic illnesses such as autism, diabetes, asthma and allergies. These children would then be evaluated every year (or possibly more frequently to account for seasonal variations in illnesses). This would take many, many years and potentially open the door to a resurgence of vaccine-preventable diseases such as diphtheria or measles.
Current ethical standards would not permit such a vaccine study, given the high risk of harm or suffering children may endure and the vast amount of research that has already addressed and confirmed the safety of vaccines. In addition, before a scientific study can be done, it must be approved by an institutional review board. No current IRB would ever approve such a study, and without IRB approval, funding would be difficult to obtain. Not to mention the study would have no credibility.
What organization, research institute or government could ever take on the risk that some children would contract a vaccine preventable disease such as Hib or pneumococcal disease? These are infections that can result in meningitis, an extremely serious disease that can result in death. In terms of safety, the track record for vaccines in smaller studies is too big to ignore compared to the risk of having a child die in such a study. Again, there are no preclinical data or epidemiological observations that would justify such a study.
Finally, parents are allowed to decide if they want to vaccinate their children; researchers and investigators are not. But in order to have scientifically sound study, children would need to be chosen at random. More importantly, to reduce confounders and eliminate bias as much as possible, the vaccination status of the child could not be revealed to the parents or the researchers. And that is why such a study would be dangerous, expensive and ultimately unethical.