Expectation shapes reality: Psychological factors predict COVID
vaccine side effects
Nov. 8, 2021: Nausea. Chills. Fatigue. Headache.
Before getting vaccinated against COVID-19, many of us braced
for the minor but uncomfortable side effects we’d heard so much
about in the news or from our friends and neighbors who had
already received the jab.
New research led by The University of Toledo suggests how
much attention people pay those fears may predict how poorly
they’ll feel post-vaccine.
In a paper published last week in the journal Psychotherapy and
Psychosomatics, researchers detailed for the first time a link
between the side effects people expected from COVID-19
vaccination and those they actually experienced.
“It’s important to see how psychological variables may be
correlated to how people respond to these vaccines,” said Dr.
Andrew Geers, professor in the UToledo Department of
Psychology and the paper’s lead author. “Our research clearly
shows that people who expected symptoms like headaches, fatigue
or pain at the injection site were much more likely to
experience those side effects than those who did not anticipate
Geers’ lab specializes in the study of social psychology theory
within health and medical contexts, including the psychology of
drug side effects, placebo effects and nocebo effects.
While it’s well documented in the scientific literature how
psychosocial factors can impact the success or side effects of a
given treatment, no one had yet done so in the context of
In April, Geers and his colleagues distributed a survey asking
unvaccinated adults in the United States about their expectation
for seven common vaccine side effects that had been widely
publicized by the U.S. Centers for Disease Control and
Prevention — pain at the injection site, fever, chills,
headache, join pain, nausea and fatigue. The survey also
collected socio-demographic information and assessed
participants’ symptoms of depression and general worry about the
Over the next three months, researchers followed up with 551 now
fully vaccinated participants to ask which of the seven
previously identified side effects they experienced.
“We found a clear link between what people expected and what
they experienced,” said Kelly Clemens, a UToledo doctoral
student studying experimental psychology and paper co-author.
“Those psychological factors are predictive over and above the
other factors that we knew were involved in predicting side
effects, such as the specific vaccine someone received, their
age or whether they previously had COVID-19.”
In addition to helping to explain why some of us felt so crummy
after vaccination and others did not, Geers and Clemens said the
study also could provide important clues for overcoming some of
the lingering vaccine hesitancy — both for first timers who are
worried about side effects and those who become eligible for a
booster dose but don’t want to go through the ordeal again.
“This really shows the power of expectations and beliefs, even
in something that we know is very physical,” Geers said. “It
appears that the effect that comes out of the vaccine is being
shaped by psychology — by expectations and worry. If we’re able
to reframe and think about side effects differently, it might
reduce the experience of side effects.”
Geers and Clemens are working with colleagues to analyze similar
data from other countries to further understand how expectations
shape reported vaccine side effects. They also plan to explore
additional data that were collected in their survey about other
side effects, side effect severity, booster dose intention and
social media use.
“This is a really great example of some of the research that our
lab does. I think it lays the groundwork for us to move forward
not only with COVID vaccines but looking at nocebo side effects
more broadly,” Clemens said. “A lot of students don’t get this
experience. Dr. Geers is an incredible mentor and he’s been
great at helping me be involved at all levels of the research.
I’m not just learning good methodology in class, but I’m also
able to put it in practice.”
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11/16/21 19:13:08 -0800.