“Nocebo” vaccine: if you expect side effects, they can occur

TUESDAY, Jan. 18, 2022 (HealthDay News) — Before receiving their first dose of a COVID vaccine, many Americans were nervous about how they would react to the vaccine, but new research shows fears of side effects may makes having side effects more likely.

To study this so-called “nocebo” effect in people receiving COVID-19 vaccines, researchers analyzed data from 12 clinical trials of COVID-19 vaccines and compared side effect rates in more than 22,000 participants who received received the vaccines and more than 22,000 who received a placebo injection.

After the first vaccine, systemic side effects – symptoms that affect the whole body, such as fever, headache and fatigue – were reported by about 46% of vaccinees.

But more than 35% of people who received the placebo also experienced similar side effects, a team of Boston investigators found.

At least one local side effect – such as pain at the injection site, redness or swelling – was reported by 16% of placebo recipients and two-thirds of vaccine recipients.

The nocebo effect accounted for many side effects in the group that received the dummy vaccine and 76% of all side effects in the vaccinated group after the first vaccine, the researchers calculated.

After the second injection, systemic side effects were reported by 32% of people in the placebo group and 61% of those in the vaccine group, and local side effects were reported by 12% of people in the placebo group and 73% of those in the vaccine group. of the vaccine group. the vaccine group.

The nocebo effect accounted for almost 52% of the side effects reported after the second dose, according to the authors of the study published on January 18 in the journal Open JAMA Network.

“Adverse events after placebo treatment are common in randomized controlled trials,” noted study author Julia Haas, a researcher in the Placebo Studies Program at Beth Israel Deaconess Medical Center in Boston.

“Collecting systematic evidence regarding these nocebo responses in vaccine trials is important for COVID-19 vaccination globally, particularly because concerns about side effects are thought to be a reason for vaccine hesitancy” , Haas said in a press release from the medical center.

“Non-specific symptoms like headache and fatigue – which we have shown to be particularly sensitive to nocebo – are listed among the most common side effects after COVID-19 vaccination in many leaflets of information,” said the study’s lead author, Ted Kaptchuk, director of the Placebo and Therapeutic Encounter Studies Program.

But giving people that kind of information could backfire, he added, causing them “to misattribute common everyday background feelings as resulting from the vaccine or cause anxiety and worry that make people hyper-attentive to bodily feelings about adverse events.”

“Medicine is based on trust,” Kaptchuk said. Letting the public know that the nocebo effect could play a role in any side effects of the vaccine “could help reduce concerns about vaccination against COVID-19, which could reduce vaccine hesitancy,” he said. -he.

More information

To learn more about the side effects of the COVID-19 vaccine, see the US Centers for Disease Control and Prevention.

SOURCE: Beth Israel Deaconess Medical Center, press release, January 18, 2022

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