More than two-thirds of the side effects associated with the COVID-19 vaccine are due to the nocebo effect, a study by Boston researchers. The researchers observed that many people in the vaccine clinical trial reported systemic side effects even though they had not received the vaccine. The results of the study were published in the "JAMA Network Open".
The nocebo effect is a derivative of the placebo effect. Placebo is a well-known phenomenon - it is where your he alth (physical or mental) improves after taking a substance that is not a drug, such as a saline injection, even though you believe you have been given medication.
The exact basis of the placebo effect is not yet well known - some theories indicate that it is due to unconscious factors embedded in the patient-doctor relationship that reduce the severity of disease symptoms. Sometimes the placebo effect can be harmful - this is the so-callednocebo effect , i.e. experiencing unpleasant side effects after using a preparation that is neutral for the body.
The placebo effect is often used in the process of researching new drugs - to check whether the drug is working, some participants get the right preparation, others receive a neutral agent (e.g. the already mentioned saline), while all are convinced that they have received proper preparation.
In a meta-analysis conducted at the Beth Israel Deaconess Medical Center in Boston, researchers compared the rates of adverse events reported by participants who received the real COVID-19 vaccine in clinical trials with the rates of adverse events reported by those given placebo. Side effects were reported more frequently by those who received the vaccine, but nearly a third of those who received the placebo also reported at least one side effect - the most common being headache and unmanageable fatigue.
As the lead author of the study, Dr. Julia W. Haas explains: “Adverse events following placebo treatment are common in randomized controlled trials. Regarding the research into new vaccines, I believe that gathering systematic evidence on the existence of a strong nocebo effect is very important.important to supporting immunization programs around the world, especially as concerns about side effects are often reported as a reason for hesitating to get vaccinated. ”
Researchers analyzed data from 12 clinical trials of COVID-19 vaccines. In total, they covered over 22.5 thousand. reports of adverse reactions from people who received placebo and 22.8 thous. from actually vaccinated patients.
After the first dose, over 35% those receiving placebo complained of systemic side effects: fever, headache and fatigue. 16 percent has reported at least one local event, such as injection site pain, redness or swelling.
For comparison: in patients vaccinated with one dose of the real preparation, 46 percent. experienced at least one systemic adverse event and two-thirds of 2/3 reported at least one local event. However, scientists believe that some of the side effects described in this group can also be attributed to the nocebo effect.
Overall, Dr. Haas's analysis found that the nocebo effect accounted for 76 percent. of all adverse events in the vaccinated group and for almost 25 percent. all reported local effects after the first dose.
In turn, after the second dose of the "vaccine" in the placebo group, 32% of respondents reported systemic adverse events. people, and the locals - 12 percent. In the second group (with real medicine), 61 percent. people experienced unwanted systemic effects, and 73 percent. - local effects.
This time, scientists' calculations showed that nocebo is responsible for almost 52 percent. all side effects after the second dose. While it is not clear what the cause of the slight decrease in nocebo effect from the first dose, Dr. Hass suggests that perhaps the high rate of adverse events in the first dose vaccinated group may have led participants to expect similar effects on the second injection.
"Non-specific symptoms, such as headache and fatigue - that is, those that most often appeared as a nocebo effect - are listed among the most common side effects after vaccination with COVID-19 in many information leaflets - says the co-author of the study, Prof. Ted Kaptchuk. Evidence shows that this type of information causes people to mistakenly attribute common ailments to everyday life to the vaccine. They are stressed and anxious from the beginning, and after vaccination they are extremely sensitive to any bodily sensations they associate with undesirable events. "
"This discovery led us toconclusion that informing the public about the potential nocebo effect can help reduce concerns about vaccination against COVID-19 and as a result - reduce the number of vaccine skeptics "- concludes the specialist.