Skeptics are quick to point to the placebo effect: The body’s capacity to heal itself after receiving only the simulated experience of medication or therapy is well documented. But precisely because that capacity is so well documented, reflexive dismissal of the placebo effect as “fake medicine” demands scrutiny—and is now receiving it. In late 2018, The New York Times Magazine reported on a group of scientists whose research suggests that responsiveness to placebos, rather than a mere trick of the mind, can be traced to a complex series of measurable physiological reactions in the body; certain genetic makeups in patients even correlate with greater placebo response.

I think the idea that we have a biological response to people showing they care about us is plausible. That would suggest it might also have a different/stronger effect than meditation. I would be very surprised if there was a measurable difference between "real" and theatrical Reiki, though.

Equivalently: It does work, as much as placebo or meditation.