Why some of the side effects of your vaccine might just be a placebo

Millions of Americans get vaccinated against covid-19 on average every day now, and as many people proudly shared their vaccination status on social networks, others will describe their mild side effects but certainly noticeable right after as a badge of honor, such as arm pain or flu-like fatigue. But not everyone’s symptoms after vaccination will necessarily be due to the vaccine – some could actually be caused by the evil twin of the placebo effect.

Just to clarify from the start, it is okay to experience side effects after vaccination, for whatever reason. If anything, these side effects are often an indication that the body’s immune system is on, as it learns to recognize what the coronavirus looks like after getting a shot of how it looks from the vaccine (usually its protein. spike, which the virus uses to infect cells). This immune response is what tends to explain symptoms like fever, fatigue, and general pain for a day or two after receiving a vaccine. Usually, but not always.

Back to 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 from side effects. About 84% had injection site reactions such as pain or itching within a week of taking a dose; 63% experienced fatigue; 55% had headaches.

Looking at these numbers alone, it makes sense that most people who get the vaccine would feel something. But surprisingly, in the same trial, a significant portion of the people who received the placebo vaccine also experienced some of these symptoms. After the first placebo injection, about a third of people reported feeling tired and about a third having a headache.. Almost 12% of people on placebo also suffered from diarrhea after the first vaccine, more than the group vaccinated after either dose. As a reminder, the people on the the placebo received only one dose of saline, that is, salt and water.

Now, some of those people who received the placebo vaccine may have experienced fatigue, headaches, or diarrhea that day no matter what, even if they had not participated in the trial – a topic that Gizmodo has covered recently before. Unfortunately, these are very common conditions caused by many different things. But some might only have experienced them because of what we call the “nocebo effect”. Just as our positive expectations can make us feel better after taking a potential new treatment, for a while at least, our negative expectations can do the opposite and make us feel miserable. On Twitter, some even admitted at feel worse after taking the placebo than after taking the real medicine later.

There is a tendency to dismiss the placebo / nocebo effect as a mere product of the mind. But every feeling that we feel is ultimately processed in the spirit, so that doesn’t say much at all. Sometimes this feeling can be attributed to a strictly physical cause – a hot stove being touched – and sometimes it’s more complicated. The stress that a person may feel about taking a newly developed vaccine, or even taking a vaccine in general, if they hate needles, could certainly be enough to trigger a headache or them. exhausting to the point of tiring.

None of this is unusual, it’s just human nature. And while it should go without saying, the origin of a person’s pain, nocebo or not, does not diminish 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, like controlled clinical trials, to better understand the world around us. This is especially important in trying to understand the potential benefits and risks of any new medicine or vaccine. Fortunately, in the case of the Pfizer / BioNTech vaccine and others like it, their benefits in protecting us from serious illness and death are become clearer every day, especially in countries with high immunization.

So go ahead and get your shot as soon as possible. Just keep in mind that your post-shot groggy might not be at the most obvious cause.