Common side effects include a sore arm, swollen lymph nodes under your arm, muscle and joint soreness, headache, fever, and gastrointestinal issues, says John E. Wherry, PhD, a professor of immunology at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia. Such reactions, he stresses, are the vaccine doing its job of inducing an immune response to protect against COVID-19.
The severity of those symptoms varies significantly. “Some people have very little besides a sore arm,” Wherry says. “Other people seem to be really knocked on their rear for the better part of the day.”
Some research suggests that women report more side effects than men, that older people may be less likely to experience side effects with certain vaccines, and that side effects are more severe after the second dose.
While side effects show that your body is responding to the vaccine, you don’t need to worry if you don’t experience any, says Schaffner at Vanderbilt. Research has shown the vaccines to be very effective in people of all ages, even older ones. So when it comes to experiencing side effects, “don’t freak out if you are, and don’t freak out if you aren’t,” Schaffner says.
If you usually sleep on one side, consider asking for the shot on the opposite arm, so the pain is less likely to bother you while in bed.
Most side effects should recede within 24 to 48 hours after vaccination.