First of all, there is no evidence that a tall glass of water will make the vaccine more effective. “Staying hydrated in general is good for your health and organ function, but it does not have any effect on the immune system’s response to the vaccine,” says Suellen Hopfer, an assistant professor … with the University of California, Irvine Program in Public Health.
Coronavirus FAQ: Why do so many folks say to drink lots of water before your vaccine?
NPR, Oct. 22, 2021
October 22, 2021