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When Do COVID-19 Vaccine Side Effects Begin?

So You Got the COVID Vaccine: How Long Until the Side Effects Kick In? Here's What to Expect

Young woman receiving a vaccine shot against a virus

By now, you've probably heard all about the side effects of the COVID-19 vaccine: sore arm, fever, chills, fatigue, headache, nausea, and more. The side effects vary depending on which vaccine you get, and they also are supposedly worse after the second shot, if you are younger, and/or if you had previously had COVID.

When Do Covid Vaccine Side Effects Kick In?

The CDC says the side effects of the Moderna and Pfizer vaccines will begin within a day or two of getting the shot. You might feel crummy enough that it affects your ability to do daily activities, such as being too tired or sick with a fever to go to work, but they should subside in a few days.

The CDC also notes that the side effects of the one-shot Johnson & Johnson vaccine include pain and swelling at injection site, tiredness, headache, muscle pain, chills, fever, and nausea. Those side effects usually start within a day or two of getting the shot but should go away in a few days. However, on April 13, the FDA and the CDC announced that federal distribution and vaccine sites will pause the Johnson & Johnson vaccine out of an abundance of caution after reports of six blood-clot cases in American women. It's worth noting that these six blood clot cases are out of the close to seven million doses of the Johnson & Johnson vaccine that have been administered so far in the United States, so it's incredibly rare.

You'll probably feel physically fine right after getting the vaccine, unless you have an allergic reaction, which is rare. The CDC notes that an allergic reaction happens within four hours of getting the shot, and could include symptoms such as hives, swelling, and wheezing. If you've had a history of allergic reactions to other vaccinations in the past, talk to your doctor about whether or not you should get the COVID vaccine. Another reaction is a rash at the injection site, which can get swollen, itchy, or red, but is considered harmless.

Everyone has a different reaction from the vaccine: some people feel like they are sick with the flu for a day or two, while others have virtually no side effects — but even if you don't experience side effects, rest assured the vaccine is still effective.

Drinking alcohol after getting your COVID vaccine isn't recommended as it could exacerbate symptoms, and anecdotal evidence suggests that hydrating in the days before and after getting your shot could help mitigate symptoms. The CDC recommends talking to your doctor to see if taking a pain reliever such as ibuprofen, acetaminophen, or aspirin to reduce any pain discomfort after getting the vaccine is right for you. If your side effects don't improve after a few days, it's time to call your doctor.

All of that aside, it's still important to get the vaccine when it's your turn to protect not only yourself from hospitalization and death from COVID, but also those around you. As unpleasant as the side effects sound, they only last a couple days and are nothing compared to the severe sickness that's possible from contracting COVID.

Image Source: Getty / Luis Alvarez
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