A literature review by researchers at Beth Israel Deaconess Medical Center, at the Harvard Medical School hospital, indicates that reactions to the Covid-19 vaccine have more to do with psychological actions than with the immunizer. The research was published in the scientific journal Jama Network Open.
The analysis involved a review of 12 articles, including adverse event reports that included 45,380 study participants.
About 76% of all common adverse reactions after the first dose and nearly 52% after the second dose are part of what they call the “nocebo effect” — a negative version of the placebo effect.
Researchers compared reports of side effects between the population who took a placebo and those who actually took the Covid-19 vaccine. While, overall, 32% of those who took the first dose of the placebo reported side effects, the number rose to 45%. In the second dose, the numbers were 31% for the placebo group and 61% for the vaccinated.
From these data, the scientists calculated how close these symptoms were to reality to estimate that they estimated that 76% of reactions to the first dose and 52% to the second were actually a nocebo effect.
Division of side effects
Of the 45,380 study participants evaluated, 22,578 were placebo recipients and 22,802 vaccine recipients. After the first dose, 35.2% of placebo patients experienced headache and fatigue. And 16% reported arm pain or swelling at the injection site.
Among those who received the vaccine, 46% were more prone to side effects and reported various symptoms, and two-thirds felt local pain.
The rate of headaches or other systemic symptoms was almost twice as high in the vaccine group (61%) compared to the placebo group (32%).
When they analyzed pain at the injection site, the difference was even greater, being 73% among those who took the vaccine and 12% in the placebo group.
The researchers believe the findings of high nocebo responses are relevant to Covid-19 vaccination in everyday health care.
“Informing the public about the potential for nocebo responses can help to reduce COVID-19 vaccination concerns, which may lessen vaccination hesitancy,” they wrote.
Reference: CNN Brasil
