Millions of Americans are being vaccinated against covid-19 on average every day now, and although many people have proudly shared their vaccination status on social media, others will describe their mild side effects, but definitely noticeable right away as a symbol of honor, like arm pain or flu-like fatigue. But not all post-vaccination symptoms will necessarily be caused by the vaccine – some may be caused by the malignant twin of the placebo effect.
Just to clarify in advance, there is nothing wrong with experiencing any side effects after vaccination, no matter the reason. At the very least, these side effects are often an indication that the body’s immune system is starting to function, as it is learning to recognize the appearance of the coronavirus after getting a plan of what the vaccine will look like (usually its peak protein, that the virus uses to infect cells). This immune response is what tends to be responsible for symptoms such as fever, fatigue and generalized pain for a day or two after you receive the vaccine. Usually, but not always.
Let’s take a look at the clinical trial data for the two-dose mRNA vaccine developed by Pfizer and BioNTech, the first to reach the American public last December. The data, based on more than 30,000 volunteers, shows that it is a safe and effective vaccine, but not free of side effects. About 84% had reactions at the injection site, such as pain or itching, in the week after taking a dose; 63% experienced fatigue; 55% had headaches.
Looking at just those numbers, it makes sense that most people who get the vaccine feel something. But surprisingly, in the same trial, a sizable portion of people who received the placebo injection also experienced some of these symptoms. After the first placebo injection, about a third of people reported feeling fatigue and about a third had a headache. Almost 12% of those who received a placebo also had diarrhea after the first injection, more than the vaccinated group after any of the doses. As a reminder, people on the The placebo received only one injection of saline, also known as salt and water.
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Now, some of those people who received the placebo injection may have experienced fatigue, headaches, or diarrhea that day, no matter what, even if they weren’t at the trial – a topic that Gizmodo has approached recently before. Unfortunately, these diseases are very common, caused by many different things. But some may have experienced them just because of what we call the “nocebo effect”. Just as our positive expectations can make us feel better after potential new treatment, at least for a while, our negative expectations can do the opposite and make us feel bad. On Twitter, some even admitted for feeling worse after taking the placebo than after taking the real medicine.
There is a tendency to dismiss the placebo / nocebo effect simply as a product of the mind. But every sensation we experience it’s basically processed in the mind, so that doesn’t mean much. Sometimes this feeling can be attributed to a strictly physical cause – a hot stove being touched – and sometimes it is more complicated. The stress that a person may feel when getting a newly developed vaccine, or even getting a vaccine in general, if he hates needles, can definitely be enough to trigger a headache or tire him to the point of fatigue.
None of this is unusual, it is just human nature. And while it may be needless to say, the source of a person’s pain, nocebo or not, does not lessen the need to recognize that pain and try to remedy it, if possible. But the placebo / nocebo effect is one of the many reasons why we need carefully planned research, such as controlled clinical trials, to better understand the world around us. This is especially important when trying to discover the potential benefits and risks of any new medication or vaccine. Fortunately, in the case of the Pfizer / BioNTech vaccine and the like, its benefits in keeping us safe from serious illness and death are getting clearer every day, especially in countries where vaccination is high.
So go ahead and get vaccinated as soon as possible. Just keep in mind that your post-shot torpor may not be the maximum obvious cause.