Here's How Long Your COVID-19 Vaccine Side Effects Might Last

The vaccines against the SARS-CoV-2 virus have not been around for very long, but the data supporting their ability to protect people from COVID-19 are strong. In the United States, the Moderna, Pfizer, and Johnson & Johnson/Janssen vaccines have all gotten emergency approval for widespread use. And while the vaccines all have slightly different levels of protection, they all do a good job of keeping people from getting severe cases that require hospitalization, or from dying of COVID-19. The other thing they all have in common? They seem to be causing a variety of side effects.

When a vaccine enters someone's body, its job is to train their immune system to recognize a potential threat. In this case, either mRNA or a modified version of a different virus is injected. The immune system doesn't know what it's seeing, so it begins to create antibodies to attack the intruder (via CDC). In some cases, the body's immune response will cause side effects that may be unpleasant. The most common side effect is pain, swelling, or redness at the site of the injection (via Mayo Clinic). But others might be more uncomfortable. These can include fever, chills, muscle pain, nausea, and vomiting, among others.

Side effects of the COVID-19 vaccine generally show up within the first three days after receiving the shot. The good news is that in most cases, these side effects are just an indication that the vaccine is doing its job, and that your body is doing its job in response. While they may interfere with your daily routine, side effects usually only last a day or two at most.

Experts at the CDC do warn that people may experience harsher side effects from the second shot than they did from the first. The minor side effects should not be a deterrent from getting the vaccine, however. The effects of getting COVID-19 can be much worse, and may even result in death. Be sure to call a doctor or health care professional if the injection site gets more red or painful after 24 hours, or if the side effects are not going away after several days. Also be aware that while rare, allergic reactions to the vaccine can occur. If you have wheezing, swelling of your tongue, lips, or eyes, or other indications of an allergic reaction, you should seek emergency care immediately.