Covid-19 vaccine: what is the nocebo effect?

If everyone knows the placebo effect, its opposite, the nocebo effect, is much less so. However, with the uncertainties related to the Covid-19 vaccine, it is becoming more and more widespread in the population. Explanations

Fever, dizziness, fatigue, nausea or even joint pain, many French people have suffered these side effects after being vaccinated against Covid-19. However, if these symptoms are real, they may be related to an unconscious action of the brain called the nocebo effect.

The nocebo effect occurs like this when a person is convinced that a product they consume or inject into them will have negative effects on their body. The brain will then somehow manufacture the symptoms on its own. Specifically, these are very real, but they are a brainchild and not a real reaction to the product.

An effect measured and supported by studies

A wave of nocebo effect was seen in 2017, when the formulation of the thyroid drug, Levothyrox, was changed. In France, this change had led to the development of symptoms in 10% of patients, although the active ingredient of the product remained unchanged.

The doubts and uncertainties about the Covid-19 vaccine had the same effect. If there are real side effects during vaccination, they are not systematic. The Pfizer laboratory saw the power of this nocebo effect during its phase 3 trials.

A first group received an injection of the Covid-19 vaccine and 35% of them said they suffered from headaches. In a second group, the injected product was only a decoy, but nevertheless it led to 29% of the volunteers to report headaches. Therefore, the nocebo effect influenced the wave of side effects that followed the vaccination of 50 million French people.

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