One of the anti-vax memes in circulation is the risk of side effects from Covid vaccines.

A meta-analysis of 12 randomized, placebo-controlled clinical trials, a team of researchers at Beth Israel Deaconess Medical Center (BIDMC) in Boston found that up to 64 percent of adverse effects may be attributable to this kind of worry. See this article in Science Alert.

Interestingly, the meta-analysis engaged with the ‘placebo effect’ as a nocebo effect, with (across the 12 trials) about half of participants taking the vaccine, the other half a placebo. The nocebo effect accounted for up to 76 percent of systemic adverse events and 24 percent of local adverse events after the first vaccine dose.

We’re unsurprised to read that non-specific symptoms (think pain, mood disorder, IBS) are particularly ‘nocebo sensitive’.