A placebo, also known as a substance without medical effects, is being used to study the reliability of reported effects of COVID-19. A recent study found that 35.2% of trial participants who received a saline solution instead of an actual vaccine against COVID-19 reported at least one adverse reaction. Those that received a vaccine and reported placebo-based symptoms demonstrated a nocebo response. During the trial, it was also found that when given a second dose, reported adverse effects went up from 46% to 61%, and the adverse effects for placebo recipients decreased from 35% to 32%. The facts that we have about placebos makes this information unsurprising.
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