By now you’re probably well aware that the COVID-19 vaccine—despite it being a life-saving shot—typically comes with at least a few less-than-pleasant side effects. They’re minor, of course: pain at the injection site, fever, fatigue—but feeling any discomfort at all isn’t exactly how you want to spend the day after getting vaccinated.
To help, some pharmacies are offering up tips on what you can do before and after your COVID shot to help reduce symptoms: According to an informational page by Walgreens, the pharmacy suggests people “eat a nutritious meal and hydrate” before their vaccine appointment to “potentially lessen any side effects.” CVS, too, urges people to “drink at least 16 ounces of water [one] hour before your appointment to help prevent side effects,” in a reminder email before their vaccine appointments.
So what exactly is going on here? Is hydration—either before or after your shot—really key to helping lessen any possible discomfort following a COVID-19 vaccine?
The truth: We don’t really know for sure—but staying hydrated isn’t usually a bad thing in any situation. The Centers for Disease Control and Prevention (CDC) recommends that those who get the vaccine stay well hydrated after the vaccine, if they end up developing a fever as a side effect. But they don’t specifically advice people to drink a certain amount of water either before or after the vaccine to help prevent side effects.
CVS, however, does suggest drinking water before your vaccine for a specific reason: to help decrease the chances of a person fainting while getting the shot.
“We added the recommendation to drink water to our vaccination appointment reminder emails in April due to some incidences of fainting we observed during the administration of a COVID-19 vaccine,” CVS spokesperson Matt Blanchette, tells Health. “Increasing intravascular volume by hydrating can help prevent a vasovagal syncope event that can lead to fainting. The CDC has also identified fainting after an immunization as a concern.” (Worth noting, the CDC says on its website that “giving patients a beverage, a snack, or some reassurance about the procedure has been shown to prevent some fainting” but adds that “studies are being done to look more into these strategies.)
“People are more likely to faint when they’re dehydrated, infectious disease expert Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security, tells Health. And though he insists that it’s purely speculation on his part, William Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine, agrees: “It’s possible that, if you were better hydrated, you’d be less likely to feel woozy.”
Past that, however, water isn’t terribly likely to help prevent side effects, per se. “Good hydration is great for general bodily function,” Dr. Shaffner tells Health. “But there’s no specific data to suggest that drinking 16 ounces of water or anything else will, in any way, enhance your immune system or specifically ameliorate side effects.”
But while water likely won’t be a magic prevention method for any post-COVID vaccine side effects, it may make you feel better in general—and that may translate into feeling a bit better if you do happen to develop side effects. “It’s just ideal to be well hydrated when getting a vaccine in terms of how one feels post-vaccine,” says Dr. Adalja. If you happen to get the vaccine while you’re dehydrated, for example, “you will feel worse and possibly get more dehydrated,” he says.
Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo, agrees. “It makes sense that you’d want to be well hydrated if you developed symptoms like a fever,” he tells Health, adding that dehydration can also “exacerbate a headache.” Still, Dr. Russo stresses that “there is no data to support that this will help with the COVID-19 vaccine.”
Still, Dr. Russo says drinking a good amount of water before your vaccine “can’t hurt”—so there’s really no reason not to down a glass before your shot, just in case.