“Nocebo effect”: two-thirds of Covid’s reactions are not caused by the vaccine, study suggests | Medical research



Researchers claim that more than two-thirds of the common side effects that people experience after a Covid stroke can be attributed to a negative version of the placebo effect rather than the vaccine itself.

U.S. scientists looked at data from 12 clinical trials of Covid vaccines and found that the “nocebo effect” accounted for about 76% of all common side effects after the first dose and almost 52%. after the second dose.

The results suggest that a substantial proportion of milder side effects, such as headaches, short-term fatigue, and arm pain, are not caused by the vaccine components, but by other factors that are thought to elicit the nocebo response. , including anxiety, expectation. and erroneously attributing various ailments to having had the jab.

In light of their findings, the researchers argue that better public information about nocebo responses may improve the absorption of the Covid vaccine by reducing concerns that cause some people to doubt.

“Telling patients that the intervention they are taking has side effects that are similar to placebo treatments for the disease in randomized controlled trials actually reduces anxiety and makes patients take a moment to consider the side effect.” , said Ted Kaptchuk, professor of global studies. health and social medicine at Harvard Medical School and lead author of the study. “But we need more research.”

Kaptchuck and Dr. Julia Haas of Beth Israel Deaconess Medical Center in Boston analyzed the adverse events reported during a dozen Covid vaccine trials. At each trial, those on the placebo arm received injections of inactive salt solution instead of vaccine. The study did not look at any serious and rare side effects, such as blood clots or inflammation of the heart.

Writing in the journal Jama Network Open, the researchers describe how after the first injection more than 35% of placebo groups experienced so-called “systemic” side effects, such as headaches and fatigue, with 16% reporting a specific place. diseases that include pain in the arm or redness or swelling at the injection site.

As expected, those who received the first injection of the vaccine were more likely to experience side effects. About 46% reported systemic symptoms and two-thirds experienced arm pain or other localized symptoms at the injection site.

When the researchers looked at side effects after the second time, they found that the rate of headaches or other systemic symptoms was almost double in the vaccine group compared to the placebo group, 61% and 32%. respectively. The difference was even greater for local diseases, reaching 73% among those who had the vaccine and 12% in the placebo group.

Overall, researchers estimate that about two-thirds of the common side effects reported in Covid vaccine trials are due to the nocebo effect, particularly headaches and fatigue, that many vaccine leaflets have. Covid is listed as the most common side effect after an injection.

While the evidence suggests that information about side effects can cause people to mis-attribute common diseases to the vaccine or make people hyper-alert about how they feel, Kaptchuk advocates more information about side effects, not less. “Most researchers argue that patients should be told less about side effects to reduce their anxiety,” he said. “I think that’s wrong. Honesty is the way to go.”

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