Nocebo is simply the opposite of Placebo.
The placebo effect occurs when a patient solely believes that they will be cured if he/she goes for a particular treatment. The Nocebo is just the opposite of this - a state in which the patient believes that a particular treatment will not work or, worse, show negative side effects.
Putting it simply - these effects are the result of the power of the mind.
This research studied twelve random trials of 45,000 people. They injected 50 percent of their subjects with the real vaccine and the other 50 percent with a harmless solution (placebo). The subjects were not told whether they were receiving a placebo or Covid-19 vaccination during the study period. Also, they were unaware that the Boston-based institution, Beth Israel Deaconess Medical Center, used two types of vaccines.
From the results, scientists concluded that more than 64 percent of adverse effects related to Covid-19 vaccinations could be really due to the nocebo effect.
Also, according to Ted J. Kaptchuk of Harvard Medical School, it is easy to experience side effects like headaches and fatigue due to the nocebo effect - as they are nocebo sensitive reactions. He added that these reactions could also be triggered when the body becomes hyper-aware during vaccination. Along with anxiety, these reactions could get attributed incorrectly to Covid-19 vaccinations.