Does Drinking Water Reduce Side Effects After A COVID-19 Shot?

Here’s what we know about how water might influence your vaccine response and general health, based on the evidence available.

Vaccination and water

Scientists have not conducted randomized trials to see how drinking—or not drinking—water before getting your injection might affect antibody levels or other immune responses. It’s a complicated question to sort out, in part because the immune response follows two main paths: In the long-term, it helps the body mount lasting defenses against the virus. On a shorter time-scale, the vaccine also causes the “innate” immune response, which is responsible for side effects some people feel after they get their shots. Researchers have conflicting opinions about water’s role in all of it.

Studies in frogs (a distant relative to humans) suggest that extreme dehydration could suppress the immune system, making it harder for cells to signal each other, says Sonia Sharma, an immunologist at the La Jolla Institute for Immunology, in California. In people, dehydration could be one of multiple stressors and poor health behaviors that delays the production of antibodies, she adds. And some research suggests that people feel more pain when they are dehydrated, says Jodi Stookey, a nutrition epidemiologist formerly at Children’s Hospital Oakland Research Institute, in California.

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But drinking too much is also a health risk, studies show, causing sodium levels to drop and leading to headaches, fatigue, seizures, even death. And plenty of experts argue that, outside the context of excessive heat or endurance exercise, healthy adults easily get enough liquids through food and beverages—even if they feel under the weather for a day or two after a vaccine shot.

And while water might play a role in preventing kidney stones and recurring urinary tract infections, for people trying to maximize their immune response while minimizing side effects, water is unlikely to do the trick on its own. “Water is not the magic bullet that’s going to give you this optimal immune response,” Sharma says. “It’s part of the cache of healthy behaviors that promote a healthy immune system.”