Updated: Apr 17, 2019
By Lindsay Aldrich
Whether or not you have brought a loved one to the pediatrician to get vaccinated, have a loved one who identifies on the autism spectrum, or have heard loved ones claim that vaccines may or may not cause autism, most of us are pretty aware at this point that there is a passionate debate surrounding this topic. But what exactly is going on behind it all? It’s complicated and easy to get confused … so let’s get started.
First, what exactly is a vaccine? A vaccine is a formulated way to deliver a pathogen, or a sickness-causing bacteria or virus, to initiate an immune response. The first time your body has an immune response to a pathogen it has never seen before, whether this be naturally or through a vaccine, your body creates unique antibodies, or immune proteins, to help kill that pathogen. These specific antibodies are then saved in your immunological memory for future use. Therefore, the next time you might be exposed to that same pathogen again, your body can easily recreate these antibodies, destroying the pathogen so quickly that you don’t even get sick.
The catch here is that when you are exposed to a new pathogen and your body doesn’t have the antibodies saved in it’s memory yet, your body is much slower at producing them and that’s when you get physically sick. The upside to vaccines is that the pathogen they expose you to has already been weakened or killed entirely. This allows your body to create those protective antibodies the first time around without causing you to suffer from the actual sickness (Pappas, 2010). But what’s the big deal about being a little sick? For some illnesses, it may not be a huge deal if you are a healthy, average-aged individual. However, for others illnesses, becoming sick from these could be life-threatening.
So, are vaccines really that successful at what they do? The short answer is absolutely. There are a few factors that may explain why some vaccines are more successful than others. For example, pathogens that have many different versions, pathogens that are found in animals as well as humans, pathogens that are contagious before symptoms are noticeable, and pathogens that don’t provide lifelong immunity are all examples that make controlling these pathogens through vaccines more difficult (CDC, 1999). An example of a pathogen like this would be the flu. The flu virus is constantly changing, passable between humans and livestock, contagious days before symptoms are present, and catchable more than once in your life. All of these factors make it harder to control the spread of the virus through a single, one-time vaccine. However, this doesn’t mean that flu vaccinations are completely useless; they are just more difficult to perfect.
On the other hand, smallpox is an example of a pathogen that is the opposite. The virus that causes smallpox has only two different versions, is only found in humans, is only contagious once fever begins, and can only be had once in your lifetime (CPP, 2019). This is why once widespread and consistent vaccination efforts were initiated, smallpox was eradicated worldwide. Before this effort in the 1950s, smallpox affected over 50 million people every year, killing 30% of those infected (WHO, 2011). However, after widespread vaccination increased global immunity, the virus could no longer survive without spreading between humans and completely died out. Now, smallpox vaccines are no longer required, as there is no perceived risk of obtaining the virus anywhere.
While today it may seem like there is less of a threat of infectious disease, there are still many diseases present around the world that have the possibility of spreading. Currently 16 of these diseases have common vaccines that can prevent them, including: chickenpox, diphtheria, meningococcal disease, haemophilus influenzae, hepatitis A, hepatitis B, human papillomavirus, flu, measles, mumps, pertussis, polio, pneumococcal disease, rotavirus, rubella, and tetanus (CDC, 2019). Each of these vaccines is approved by the Food and Drug Administration (FDA), recommended by the Centers for Disease Control and Prevention (CDC), and ensured to be safe with only a few possible side effects such as soreness, fever, and aches (USDHHS, 2019).
So if vaccines are really that safe, then why do some people believe that autism could be caused by them? This idea was first introduced by a doctor named Andrew Wakefield. In 1998, Wakefield published an article in the Lancet journal studying 12 children who exhibited autism symptoms after administration of the MMR vaccine, a vaccine that prevents measles, mumps, and rubella all in one shot. His theory was that in some cases, the combined MMR vaccine may be too taxing on the immune system and could allow the measles virus to linger in the digestive system, leading to bowel disease. He then suggested that prolonged bowel disease may be related to autism (CPP, 2019).
However, the claim that vaccines could directly cause autism went viral almost immediately. Concerned parents started resisting the MMR vaccine out of fear for their children, and parents of children with autism were also given a platform to speak about their experience - how their child also displayed autism symptoms around the time of the MMR vaccine. The abundance of these personal narratives emerging about autism appearing after MMR vaccines seemed to give credibility to this claim.
However, as public belief that vaccines may cause autism increased, belief within the scientific community began to prove otherwise. Hundreds of scientists found Wakefield’s research to be non-reproducible, calling his methods into question. Once under investigation, Wakefield’s research was found to be extremely flawed and biased. For example, Wakefield’s research described that six out of the 12 children he studied had bowel disease and autism symptoms appearing strictly after the MMR vaccine. In reality, communication with the parents of these children, along with hospital records, showed that none of the children truly had this experience (Deer, 2011). Wakefield also failed to disclose the fact that he had been funded by lawyers hoping to sue vaccine manufacturers based on the claim he would end up publishing - a serious conflict of interest. Further, his primary argument was to separate the MMR vaccine and recommended switching to singular vaccines, all while he had coincidentally filed a patent for a singular measles vaccine in 1997 - a year prior to his call for it as a solution (CPP, 2019). In the end, Wakefield was charged with falsifying data, his paper ended up retracted from the Lancet journal, and his medical license was taken away due to severe misconduct (GMC, 2010).
While Wakefield’s original study was disproven, public fear regarding vaccine safety, particularly regarding the MMR vaccine, continued to grow, inspiring an array of responsive research being performed in new and highly specified areas. The fears continue to evolve and include concerns about the combined MMR vaccine compared to singular vaccines, the timing or immunization schedule of the MMR vaccine, certain substances found in the MMR vaccine such as mercury, and the MMR vaccine being given at all. In addition, new fears have been created everyday, suggesting that maybe it’s the fevers, inflammation, or possibly an unknown link between the two that we have just not yet figured out. And while it may seem impossible to test everything, scientists remain confident that the MMR vaccine does not cause autism.
You may be wondering then, how is it possible to know this? The answer lies in the difference between correlation and causation. While the administration of the MMR vaccine and the timing of autism symptoms may seem to be related, or correlated, they are not causal. This can be determined based on the fact that regardless of how many times experimental groups are manipulated to change the vaccine schedule, ingredients, side effects, or administration at all, autism rates stay identical between vaccinated and unvaccinated populations, suggesting that there is no way these two factors can be causal if the manipulation of one has no effect on the other. Instead, similarities in the timing of vaccines and the onset of autism can be explained by the fact that both are independently seen at around the same time of a child’s life (SARRC, 2019).
A common analogy illustrating this subtle difference between correlation and causation would be the phenomenon that when ice cream sales increase, so do murder rates (Marchand, 2017). When looking at this fact, you may start to wonder if ice cream shops may indeed lead to more murder. However, when research is done showing that reducing the number of ice cream shops open at once, spacing ice cream shops out differently, removing certain flavors of ice cream in shops, or shutting down ice cream shops entirely all have absolutely no effect on murder rates, there is no way that these two factors can be causal.
Instead, it is likely due to the fact that these separate factors have similar time frames, as both ice cream sales and murder rates tend to increase during the summer (Marchand, 2017). While it may look like ice cream shops cause murder, we know that this is not true. In addition, if there is not only an abundance of research proving that ice cream sales and murder rates are independent, but also an abundance of research proving that ice cream has many positives, including making our children happy, then we may want to rethink how we use our research and its data to choose what’s best for our children.
Centers for Disease Control and Prevention (CDC). (2019) Easy-to-read Immunization Schedule by Vaccine for Ages Birth-6 Years. Retrieved from https://www.cdc.gov/vaccines/schedules/easy-to-read/child-easyread.html
Centers for Disease Control and Prevention (CDC). (1999) The Principles of Disease Elimination and Eradication In: Global disease elimination and eradication as public health strategies. MMWR 1999;48(Suppl).
Deer, B. (2011). How the case against the MMR vaccine was fixed. Bmj, 342(Jan05 1), C5347-C5347. doi:10.1136/bmj.c5347
General Medical Council (GMC). (2010) Fitness to Practice Panel Hearing for Dr. Andrew Jeremy Wakefield. GMC reference number: 2733564. Retrieved from http://briandeer.com/solved/gmc-charge-sheet.pdf
Marchand, A. (2017, June 18). Why Ice Cream Isn't Deadly: Correlation vs. Causation. Retrieved from https://plebeianscience.wordpress.com/2017/06/18/why-ice-cream-isnt-deadly-correlation-vs-causation/
Pappas, S. (2010, June 01). How Do Vaccines Work? Retrieved from https://www.livescience.com/32617-how-do-vaccines-work.html
Southwest Autism Research & Resource Center (SARRC). (2019, February 13). Vaccines and Autism. Retrieved from https://autismcenter.org/vaccines-and-autism
The College of Physicians of Philadelphia (CPP). (2019). Do Vaccines Cause Autism? Retrieved from https://www.historyofvaccines.org/content/articles/do-vaccines-cause-autism
The College of Physicians of Philadelphia (CPP). (2019). Disease Eradication. Retrieved from https://www.historyofvaccines.org/content/articles/disease-eradication
U.S. Department of Health & Human Services (USDHHS). (2019). Vaccine Side Effects. Retrieved from https://www.vaccines.gov/basics/safety/side_effects
World Health Organization (WHO). (2011). Bugs, Drugs and Smoke: Stories from Public Health. Geneva400025384987.