‘Nocebo’ effect is responsible for some COVID vaccine symptoms: study

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For those who suffered side effects after the COVID vaccination, the adverse symptoms were probably worth it, even if they didn’t really have to feel them.

According to the US Centers for Disease Control and Prevention, about 77% of those who received a vaccine dose from Pfizer, Moderna, or Johnson & Johnson reported at least one nonlocal symptom soon after the vaccine, such as headache, fever, fatigue and muscle pain.

But a new study published Tuesday in the journal JAMA Network Open found that nearly two-thirds of these symptoms were likely self-induced via what researchers call the “nocebo effect.”

Scientists at Beth Israel Deaconess Medical Center in Boston found that many volunteers in vaccine control groups — those who had unknowingly received an inert placebo vaccine — claimed to have suffered from the same flu-like symptoms as their vaccinated cohorts.

New findings suggest that around two-thirds of reported symptoms following the COVID-19 vaccine were likely self-induced via the ‘nocebo effect’. Shutterstock

“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,” study lead author Ted J. Kaptchuk, a professor of medicine at Harvard Medical School, said in a statement.

“Evidence suggests that this type of information can cause people to mistakenly attribute common daily background feelings as resulting from the vaccine or cause anxiety and worry that makes people hyper-alert to bodily feelings about the adverse events,” Kaptchuk added.

The researchers found that vaccine and placebo recipients reported adverse effects at similar rates – 22,802 and 22,578 reports, respectively – according to data collected from 12 recent vaccine trials.

Over 35% of placebo recipients experienced at least one systemic symptom, that is, not associated with the injection site. Headaches were the most common, with 19.6% reporting, followed by fatigue at 16.7%. By comparison, 46% of true vaccinates reported experiencing at least one systemic symptom.

Meanwhile, 16% of placebo recipients also reported local effects, such as pain, itching and swelling at the injection site after the first dose, while around 66% of volunteers who were actually vaccinated experienced the same local effects. .

The figures reveal that at least some of the side effects – about two-thirds – reported by people who received active vaccine treatment can be attributed to the nocebo effect, as many of the same symptoms occurred in the placebo group, according to the researchers. .

As participants progressed to additional doses, the number of those reporting adverse symptoms after a second placebo injection fell to 32%, and local site discomfort to 12%.

But for the group vaccinated in good faith, their reporting of a systemic reaction jumped to 61% and injection site effects jumped to 73%. Researchers believe this may be the result of participants anticipating symptoms from their second dose, eliciting a psychosomatic response that matched their expectations.

The study then suggests that the nocebo effect may be responsible for up to half of all side effects reported after the second dose, for those receiving two-dose therapies, such as those from Pfizer and Moderna.

The researchers acknowledged limitations in that the 12 trials they included in the review took different approaches to signaling symptoms and used various types of vaccines – mRNS, protein-based and viral vector-based.

Kaptchuk said he hopes their study “may help reduce concerns about COVID-19 vaccination, which may reduce vaccine hesitancy.”

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