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. The results of the meta-analysis were published in JAMA Network Open.
A placebo is a substance with no real medicinal properties, which is used in clinical trials in order to evaluate the effect of a real drug. The placebo effect can only occur if the person believes in the effectiveness and inspires himself that the dummy works.
Nocebo 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.
Despite the fact that information about the side effects of vaccines can cause fear of them and increased attention to one’s well-being after a dose of the drug, study leader Ted Kapchuk urges not to be silent about possible reactions, but to explain even more than they do now to calm people and resolve their doubts.
Today, vaccination against covid is already carried out among children. So in Russia it was allowed to vaccinate schoolchildren from 12 years old, and in the USA they began to vaccinate children from 5 years old.