Cross posting as pertinent to this thread also:
This
recently reported research is interesting
Nocebo responses explain up to 76% of COVID vaccine (systemic) side effects
Some vaccine side effects are very real, but many may be anxiety and mis-attribution.
The harmless interventions (ie faux vaccines in the control half of a trial) can lead people to report harmful side effects, particularly when people are expecting such side effects. Researchers have coined these phantom adverse reactions "nocebo responses." Nocebo responses are thought to stem from expectations of side effects, anxiety-induced effects, and the mistaken attribution of common, non-specific ailments, like headaches, to the placebo.
This Harvard study quantified just how big a role they played: it
used meta-analysis (18 Jan JAMA Network Open). It looked at vaccine side-effect data from the many clinical trials. It concluded that nocebo responses accounted for 76% of
systemic adverse reactions—like headache, fever, and chills—after the first vaccine dose and 52% of systemic reactions after the second vaccine dose.
There was a clear difference in the
local (eg upper arm) side effects. Only 16% of placebo recipients reported local side effects, like pain or swelling at the injection site, while 67% of the vaccine group reported such effects.
Overall the nocebo response rate clearly seems to be skewing our experience with COVID-19 vaccines: the researchers argue that highlighting the potential for nocebo responses could reduce side effects and help improve vaccine uptake.