Don't Get a Booster Shot Without Doing This First, Experts Warn
Make sure you're prepared before you get your next COVID vaccine dose.
More than 30 million people in the U.S. have gotten a booster COVID shot already, according to the latest data from the Centers for Disease Control and Prevention (CDC). Only some people are technically eligible for an additional shot right now, as both the CDC and the U.S. Food and Drug Administration (FDA) are still deliberating opening up qualifications for third doses. Several states, including New York, Colorado, New Mexico, and Arkansas, have recently bypassed these agencies, however, and are already recommending that health care providers in these states provide an additional shot to anyone over the age of 18, expanding booster eligibility to millions more residents. But if you're planning to get your booster soon, you have to make sure you're fully prepared for your appointment.
Major pharmacies have recently been warning people scheduling booster shots to drink water beforehand. "Be sure to eat a nutritious meal and hydrate before your appointment to potentially lessen any side effects on the day of your vaccination," Rite Aid states it its guidelines. CVS also advises people to "drink at least 16 ounces of water [one] hour before your appointment to help prevent side effects" in a reminder email that is sent before their appointment, per Health.
According to the CDC, reactions reported after the booster shot have been similar to that of the second shot of a two-dose series or the single shot of a one-dose series. The most common booster side effects have been fever, headache, fatigue, and pain at the injection site.
But other experts warn that drinking a glass of water won't actually prevent side effects. "There's no specific data to suggest that drinking 16 ounces of water or anything else will, in any way … specifically ameliorate side effects," William Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine, told Health.
Instead, experts say it is important to note that not being hydrated before your booster appointment is likely to make you feel even worse. "Being dehydrated increases your risk of feeling ill or fainting just as you might be dealing with vaccine side effects," Amesh Adalja, MD, a senior scholar at the Center for Health Security at Johns Hopkins, told NPR. "Don't take a vaccine or booster after running a marathon and becoming dehydrated."
Matt Blanchette, a spokesperson for CVS, told Health that this is the actual reason the pharmacy has started to warn people to drink a glass of water before coming in for their appointment. "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," Blanchette explained.
He added, "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."
You might be tempted to try to get ahead of your side effects before receiving your shot in other ways, especially if you've already experienced unpleasant reactions from the first or second shot. But experts explicitly warn against taking over-the-counter (OTC) pain relievers before getting your original vaccine or booster shot.
"It is not recommended you take over-the-counter medicine–such as ibuprofen, aspirin, or acetaminophen–before vaccination for the purpose of trying to prevent vaccine-related side effects," the CDC states. "It is not known how these medications might affect how well the vaccine works. However, if you take these medications regularly for other reasons, you should keep taking them before you get vaccinated. It is also not recommended to take antihistamines before getting a COVID-19 vaccine to try to prevent allergic reactions."
As GoodRx Health explains, there are no specific studies yet on how OTC medications might affect your immune system's response to the COVID vaccine or booster. With other vaccines, however, research has shown that certain pain relievers might cause a weaker response to the vaccine, which could potentially make the shot less effective.
Thankfully, drinking water won't impact your vaccine's effectiveness either way—so it's a safe way to try to mitigate feeling worse that won't affect how your booster works. "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," Suellen Hopfer, PhD, an assistant professor of health, society, and behavior with the University of California, told NPR.
In a statement to Health, Thomas Russo, MD, a professor and chief of infectious disease at the University at Buffalo, added that drinking a good amount of water before your booster shot "can't hurt," so you might want to make sure to up your intake before your appointment just in case.