Many mild, adverse reactions to the COVID-19 vaccine, such as headaches and fatigue, could be attributed to a negative version of the placebo effect, a group of researchers suggests.
In a study published today (January 18) in JAMA Network Open, scientists found that, in placebo-controlled COVID-19 clinical trials, 35 percent of placebo recipients reported adverse side effects compared to 46 percent of vaccine recipients after one vaccine dose. After two doses, 32 percent of placebo recipients reported side effects compared to 61 percent of vaccine recipients. For placebo recipients, headache, fatigue, and arm pain were the most common side effects reported.
The placebo effect typically refers to beneficial effects of a drug that derive from the recipient’s expectations of its effects rather than its biochemistry. The effect can also work in reverse, causing adverse effects comparable to known effects, a phenomenon called the “nocebo” effect.
Read more at The Scientist.