Vaccine Misconception of the day-It happened after the vaccine therefore it was caused by it
As you research vaccines, you will inevitably come across stories like this one, detailing something bad happening right after vaccines were administered. Some times, right after means a few hours; other times right after means days or even weeks. Unfortunately, it is an all too human reaction to try to causally connect two events that follow each other in time. Event A happens; some time after event B happens and our natural propensity is to assume that A caused B, simply because B follows A in time. However, it behooves us to understand that it need not be so, that this is a common type of logical fallacy. When this sort of sequence of events occurs, people try to figure out what they did out of the ordinary prior to the bad event happening, and that leads to the post hoc fallacy.
To help drive this point home, think about the current egg recall in the United States. As you may know, a major egg recall is in effect due to salmonella contamination. For purposes of our exercise we will assume that you love eggs, and every morning prepare yourself an omelet. Unbeknown to you, you purchase contaminated eggs. You cook them and consume your omelet. The next day you repeat the process, but also go to check out a new restaurant that opened in your neighborhood. The third day, you consume another egg, and a short time after you become sick and the doctor tells you that you have salmonella.
If you didn’t know about the contaminated eggs, the natural propensity would be to assume that you got sick at the restaurant, not from the eggs. The same logic would be in play here: the only thing you did differently was going to the new restaurant, and you got sick right after eating at the restaurant. The disease followed eating in the restaurant temporally, therefore it must have been caused by it, the fallacy goes. Clearly you would be wrong in your conclusion, as it was the eggs that made you sick. This is why the post hoc fallacy is a fallacy. Just because something follows something else temporally, it does not mean it was caused by it.
The same applies to vaccines. Just because a disease is diagnosed “right after” some vaccines, does not logically lead to the conclusion that it was caused by the vaccines, especially if we play fast and loose with the definition of “right after”. The only way to establish a causal relationship is through large-scale, randomized, double-blind, scientific studies examining the supposed connection between the two events. So far the evidence does not support most of these claims; vaccines have not been linked to autism.
However, vaccines are not 100% safe, just like all other medicine we use they have side effects, mostly mild, but in very rare cases severe. Overall, we must do a cost benefit analysis, as we do with everything else. The harm that is prevented through vaccines, the lives saved, the suffering avoided, hugely overshadows the harm caused by vaccines. This does not mean we should be happy and willing to live with the side effects; if they can be reduced even further we should strive for that, the same way we should strive to improve airplane technology; cars, car seats etc.