American epidemiologists have calculated that about 76 percent of systemic adverse reactions after the first dose of coronavirus vaccines and 52 percent of systemic reactions after the second dose can be explained by the nocebo effect – self-hypnosis and the expectation of negative consequences. To find out, the researchers performed a meta-analysis of 12 studies that included a total of 45,380 participants. Meta-analysis results published v JAMA Network Open.
Under placebo understand a substance without real medicinal properties, which is used in clinical trials in order to evaluate the effect of this drug. The placebo effect can only occur if the person believes in the effectiveness and inspires himself that the dummy works.
Nocebo – this is the antithesis of placebo, also a substance without real pharmacological properties, but, unlike placebo, it causes a negative reaction in the patient, because people expect a negative effect from the drug. The nocebo effect can often be seen in clinical trials when patients report side effects after taking a dummy drug.
Clinical trials of coronavirus vaccines were no exception. To figure out how common the nocebo effect is among their participants, decided American researchers led by Ted Kaptchuk (Ted J. Kaptchuk) from Harvard Medical School. They performed a meta-analysis of 12 studies with a total of 45,380 participants. All studies examined the effectiveness of coronavirus vaccines in two groups of participants: one received a real drug, and the other received a dummy.
After the first dose in the placebo group, 35 percent of participants reported systemic adverse reactions (headache in 19 percent and fatigue in 17 percent). Among the people who received the vaccine, there were more such participants – about 46 percent. After the second dose, 32 percent of people in the dummy group and 61 percent of the drug group reported side effects. The difference in the number of side effects between the experimental and control groups was statistically significant, but the scientists calculated that the nocebo effect was responsible for 76 percent of systemic adverse reactions after the first dose and 52 percent after the second dose.
Although information about the side effects of vaccines can cause fear of them and increased attention to their well-being after a dose of the drug, study leader Tad Kapchuk calls not to withhold information about possible reactions, but to explain even more than they do now in order to reassure people and resolve their doubts.