Expectations May Influence Vaccine Side Effects

If you think the COVID-19 vaccine is going to make you feel sick, you might be right.

But it might not necessarily be the vaccine that’s producing those effects. It could be your own head.


A recent study suggests that a “nocebo” effect – a fear of vaccine side effects – may be a large contributing factor to any side effects a vaccine might cause.

Researchers analyzed data from 12 clinical trials of COVID-19 vaccines and compared rates of side effects in more than 22,000 people who received the vaccine and more than 22,000 who received a placebo.

Forty-six percent of vaccine recipients reported “systemic” side effects like fever, headache, and fatigue. But more than 35 percent of placebo recipients experienced the same things.

The team indicated that the nocebo effect accounted for almost all of the side effects of the group that got the dummy shot (outside of pain at the injection site, redness) and about 76 percent of the people that got the actual shot.

After the second shot, researchers figured that the nocebo effect accounted for about 52 percent of reported side effects.

Some of the non-specific COVID vaccine symptoms, like headache and fatigue, are listed as some of the most common adverse reactions to the shot. They also, however, seem to be particularly nocebo-sensitive.


This matters because one of the biggest causes of vaccine hesitancy is the potential of uncomfortable side effects. But this study suggests at least a link between expectation and result.

If you think you are going to experience a side effect or are afraid of feeling a side effect, the results of this work suggest you may be more likely, and likely are, experiencing them based on your expectations.

If the fear of side effects has been holding you back from vaccination or a booster, try to change your view. Or accept the idea that a few days of discomfort can help keep you and your loved ones healthy while potentially taking some stress off of a fragile healthcare system.

Author Bio

About eight years ago, Mat Lecompte had an epiphany. He’d been ignoring his health and suddenly realized he needed to do something about it. Since then, through hard work, determination and plenty of education, he has transformed his life. He’s changed his body composition by learning the ins and outs of nutrition, exercise, and fitness and wants to share his knowledge with you. Starting as a journalist over 10 years ago, Mat has not only honed his belief system and approach with practical experience, but he has also worked closely with nutritionists, dieticians, athletes, and fitness professionals. He embraces natural healing methods and believes that diet, exercise and willpower are the foundation of a healthy, happy, and drug-free existence.


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