Meta research (an aggregation and analysis of related research efforts) has revealed a curious ‘nocebo effect’ related to reaction to Covid-19 vaccinations.

” … Researchers at Harvard Medical School and Beth Israel Deaconess Medical Center compared the rates of adverse events reported by participants who received the vaccines to the rates of adverse events reported by those who received a placebo injection containing no vaccine.

Although the scientists found significantly more trial participants who received the vaccine reported adverse events, nearly a third of participants who received the placebo also reported at least one adverse event, with headache and fatigue being the most common.”