Sore arm, strong immunity! If your arm is feeling a bit tender after getting your seasonal vaccines, you're not alone. This pain is a good sign that your immune system is making antibodies in response to the viruses in the vaccine. If your arm hurts after a vaccine, there are some actions you can take: - Move your arm around after the vaccine. If you try to keep too still, it may hurt more. - Take a pain reliever for one or two days after receiving the vaccination to help with soreness and swell