At least two-thirds of the common side effects experienced by those vaccinated against Covid-19 can be largely explained by the “placebo” effect and not by the vaccine itself, according to a new US study.
“Placebo” refers to the improvement of physical or mental health after a virtual treatment, such as a pill without active ingredient, injection containing only salt water, etc. The reverse phenomenon is “nocebo”, when one feels unpleasant side effects, such as nausea or fatigue, after receiving virtual therapy, which in fact does not contain any active substance. The placebo / nosibo twin phenomenon is a typical case of the power that mental and psychic factors have in influencing a person.
Researchers at the Beth Israel Deaconess Medical Center in Boston, led by Dr. Julia Haas and Harvard University School of Medicine professor Ted Kapchuk, director of the Placimbo Research Program, published the publication on , evaluated (meta-analyzed) data from 12 randomized, placebo-controlled clinical trials of Covid-19 vaccines, which included reports of side effects from nearly 23,000 people who had been vaccinated regularly and about as many who had received a placebo.
After the first dose, more than one in three (35%) who had been given a placebo pseudo-vaccine reported systemic side effects such as fever, 20% headache, 17% fatigue and 16% pain, redness or swelling at the injection site. By comparison, 46% of those who had actually been vaccinated reported at least one systemic side effect such as fever, while two-thirds reported some other local symptom.
The researchers took it for granted that a significant proportion of these side effects in vaccinated individuals were due to the placebo / nosibo effect and not to the vaccine itself, given how often the same side effects were reported by people who thought they had been vaccinated. The study, according to Haas, estimated that 76% (three-quarters) of all first-dose side effects among those vaccinated were most likely related to placebo / nosibo.
After the second dose, systemic side effects in the placebo group were 32% and local 12%, while in the vaccine group they increased to 61% and 73% respectively. The researchers estimated that half (52%) of these side effects in those vaccinated with the second dose were due to placebo / nosibo. The scientists estimate that the second time the vaccinated people expected to have more side effects than the first dose and … they justified themselves.
Haas pointed out that unfortunately “concerns about side effects are one of the reasons for hesitations about vaccination”. “Medicine is based on trust, and our findings lead us to inform the public about the potential effects of nosibo that can help reduce concerns about Covid-19 vaccines and reduce reluctance to do so,” Kapchuk said. ».
Link to the scientific publication: https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2788172
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