The internet is filled with stories about COVID-19 vaccine side effects like headaches, high heart rates, low-grade fevers, chills, fatigue, fogginess, muscle pain (especially at the injection site), achy joints, and lightheadedness that can linger for a few days.

It’s to be expected, says Megan Roche, M.D., who is pursuing a Ph.D. in epidemiology and is a coach at SWAP Running.“Your body is having an antibody party,” she says. “A fundamental, key component of that antibody party is inflammation.”

And that can lead to what feels like a miserable hangover.

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Women tend to have stronger side effects than men, according to the Centers for Disease Control and Prevention (CDC), which may be related to estrogen’s influence on the immune system. Some women have also been reporting some short-term changes to their menstrual cycle, like worse PMS symptoms, heavier cycles, shorter cycles, missed cycles, and/or spotting. Researchers are tracking this phenomenon to determine if there’s an actual connection, but it’s not uncommon for the menstrual cycle to be disrupted by stress and inflammation.

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The second shot of two-shot vaccines may bring on more pronounced side effects than the first, because your immune system now recognizes the virus and mounts a more robust response.

As happy as we are to have vaccines, the side effects are a bit of a bummer when the weather is getting warmer and races and events are starting to resume. But it definitely beats getting COVID-19, which can cause long-term symptoms such as fatigue and loss of smell and taste months after even a mild case of the disease.

Getting the vaccine doesn’t mean you need to let up on your goals, though. You just need to plan your training around your shots to let your body’s immune system do its job without piling on additional stress that will only make you feel worse. Here’s how.

Training Post-COVID-19-Vaccination

Sedentary folks may only feel out of it for a day or two, because they’re not out there pushing themselves. Athletes may be more likely to notice symptoms and/or experience them longer because a) they’re trying to perform at higher levels and b) training is a stress that also causes inflammation, so when you layer inflammation on inflammation, you can have a more pronounced response.

A study published earlier this year in The Lancet suggests that athletes may want to consider reducing their training load in the first 48 to 72 hours after their COVID-19 vaccination, especially after the second dose.

“It’s really important to listen to yourself,” Roche says. “We recommend that athletes take one rest day after their first shot and then start back gradually with an easy day or two as needed. After the second dose [or the first dose if it’s the one-dose Johnson & Johnson vaccine], take one or more rest days as needed and then two to three easy days to ease back into training.”

Also don’t be surprised if your response isn’t linear, Roche says. “You may feel great two to three days after the vaccine and then five to seven days out be hit with a wall of feeling rough. Your body might be operating on a different inflammation timeline, or it is possible that the cortisol from your training is interacting with the inflammatory response.”

The most important thing is to give yourself a grace period and also realize that you may experience some mood disturbances both from the inflammation and because your training, which helps relieve stress and stabilize your moods, is disrupted.

“I knew what was happening—I study this stuff—and I was still a little freaked out when my training was affected for seven to 10 days. But after two weeks, I was 100-percent normal again,” Roche says.

You can help take the pressure off yourself by planning your training accordingly, and aiming for events that are several weeks out from our second dose, says sports medicine physician Kevin Bernstein, M.D, competitive cyclist, and chief medical officer for Peaks Coaching Group, who created a webinar on COVID-19 vaccines for endurance athletes.

“If you’re doing training blocks with three weeks on and one week off, plan that lower volume week around your vaccination [if possible], so you’ll naturally build back up,” Bernstein says.

It’s also important to note that you may not feel too bad after either shot and that’s perfectly normal, too, says infectious disease researcher S. Wesley Long, M.D., Ph.D., who is a clinical pathologist and microbiologist and at Houston Methodist, and who has researched COVID-19 and the various new strains.

“You don’t need to have a big reaction to have an effective immune response,” Long says. Indeed, SWAP Running coach David Roche says one of their athletes won a 100K ultra running race just four days after her second shot.

The most important thing is for people to know that any side effects are temporary and to get their shots, Long says. “We need people to keep getting vaccinated to protect ourselves, protect against variants, and finally put an end to the pandemic.”

Headshot of Selene Yeager
Selene Yeager
“The Fit Chick”
Selene Yeager is a top-selling professional health and fitness writer who lives what she writes as a NASM certified personal trainer, USA Cycling certified coach, Pn1 certified nutrition coach, pro licensed off road racer, and All-American Ironman triathlete.