For several years, the debate over Covid-19 vaccines has been marked by uncertainty surrounding side effects and long-term symptoms.
The issue has influenced both willingness to be vaccinated and trust in health authorities.
According to researchers, it is therefore essential to distinguish between documented associations and self-reported symptoms.
A large Danish cohort study now contributes insights that extend beyond individual vaccines and feed into a broader discussion about expectations, health behavior, and communication.
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The study was conducted in collaboration between Aarhus University, several university hospitals, and Aalborg University, with external funding from the Tryg Foundation and the Independent Research Fund Denmark.
What the study found
The study, published in the International Journal of Epidemiology, followed more than 90,000 Danes over time.
Participants were grouped according to their attitudes toward Covid-19 vaccines, and researchers compared the occurrence of non-specific, long-term symptoms among vaccinated and unvaccinated individuals.
The researchers behind the study conclude that the majority of participants show no indication that vaccination itself leads to persistent symptoms.
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This observation differs from earlier, smaller studies due to its scale and its inclusion of participants’ expectations as an analytical factor.
Interpretation and perspective
Only within a smaller group with pronounced concerns did researchers find higher levels of reported symptoms.
PhD student Christina Bisgaard Jensen from the Department of Public Health at Aarhus University points to the nocebo effect as a possible explanation.
She says in a press release from Aarhus University: “The symptoms are entirely real for those who experience them. But that does not necessarily mean that the vaccine is the cause”.
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She emphasizes that reported side effects cannot be understood in isolation from psychological and social factors.
Sources: Press release from Aarhus University, Nyheder 24, and International Journal of Epidemiology.
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