Here’s Everything That Could Happen to Your Body When You Get the COVID Vaccine

Plus, a doctor answers if you can actually prevent the side effects.

Now that people all over the country are scheduling their COVID-19 vaccines, it’s time to think about what comes along with the shots. After all, in addition to peace of mind and new freedoms comes the very real chance of side effects. Don’t let that scare you, though. Instead, keep reading to learn what can happen to your body when you get the COVID vaccine, including what symptoms are normal and which could be a sign of something more.

COVID vaccine side effects, first dose:

As with any vaccine, Verywell Health chief medical officer, Jessica Shepherd, says that side effects associated with the Pfizer, Moderna, and Johnson & Johnson vaccines can range from mild to sometimes more severe reactions—and can sometimes make you feel like you’re actually sick with what you’re trying to prevent against.

“These side effects do not indicate having the disease but are normal signs that your body is building protection,” she says, offering reassurance. “These side effects—which could include pain, redness, or swelling at the injection site, as well as fever, fatigue, headache, muscle pain, and chills—may be mildly noticeable and sometimes take you away from some daily activities, but usually go away in a few days.”

If you have a severe allergic reaction to the vaccine, however, Baltimore-based internal medicine physician, Dr. Vivek Cherian, says that anaphylaxis can occur. However, that type of reaction is very rare. “Most often these occur in people known to have had severe reactions to vaccines in the past,” he offers as reassurance. “Anaphylaxis typically occurs shortly after vaccination and that’s why people are observed for at least 15 [to 30] minutes after receiving the vaccine.” So just know that you’re in very good hands when receiving the vaccine.

COVID vaccine side effects, second dose:

If you’ve been discussing the COVID-19 vaccine in your family and friend circles, chances are you’ve heard that some people—especially older people—find that they experience more side effects following the second dose (such was the case with both of my parents). Fear not though, this is totally normal.

According to Dr. Cherian, any of the symptoms mentioned above can occur after either your first or second dose. “However, it’s not uncommon to have more side effects, especially after your second dose,” he says. “The reason for this is because the body has already started to develop antibodies (it has already been primed) after your first dose and your body responds more robustly after your second dose.” The good news is the Centers for Disease Control and Prevention (CDC) says these side effects should also go away within a few days.

Who is most likely to experience symptoms?

It’s hard to say, for everyone takes to vaccines differently. “In general, no one is more likely to experience symptoms,” Dr. Cherian says. “There is one big exception, though: If you have had a severe allergic reaction or an immediate allergic reaction to previous vaccines in the past that have the same ingredients as either mRNA vaccine (Moderna and Pfizer vaccines) or the same ingredients in the Johnson & Johnson vaccine, you should not take the vaccine because you have a higher chance of developing the same allergic reaction when getting one of the COVID-19 vaccines.” As always, make sure to consult your doctor before getting the vaccine if you are eligible to find out what you can do if this applies to you.

When do post-vaccine symptoms require medical care?

As a general rule of thumb, Dr. Cherian suggests seeking medical attention if any symptoms grow in severity and persist for more than three days. “It is never a bad idea to give a call to your doctor,” he says, noting that if you ever feel like you may be having a severe allergic reaction (difficulty breathing, swelling of the face and throat, rash, or low blood pressure) you should seek immediate medical assistance by calling 911.

While that last bit alone could cause caution, know that the number of severe adverse reactions to the vaccines is incredibly low. “There have been very few severe reported reactions to the vaccine that include acute allergic reactions, defined as itching, rash, hives, swelling, and/or respiratory symptoms,” Shepherd shares. “These reactions are rare and have been reported at less than 2%.” Still, if you notice any change in cardiovascular or respiratory function, it is important to seek immediate care. Here is a What to Expect After COVID Vaccine Guide from the CDC.

Can you prevent the side effects?

While you can’t 100% prevent COVID-19 vaccine side effects (given you don’t know how your body will react to the shots), there are ways to give yourself the best odds. After getting the vaccines, Shepherd recommends using an ice pack or cool compress to reduce any redness or swelling at the injection site and to drink plenty of fluids in the two days following the shot(s).

Dr. Cherian adds to this, noting that he recommends taking OTC medications such as acetaminophen (Tylenol) every eight hours or so for the two days following the shot(s)—doing so will help prevent inflammation as well as general feelings of achiness and fatigue. “It is important not to take these medications before getting the COVID-19 vaccine as they could possibly reduce the vaccine’s effectiveness,” he adds. According to CDC, “it is not known how these medications might affect how well the vaccine works.” However, if you do take these pills on the regular, then it’s recommended to still take them as usual.

Another way to help your body strengthen itself in an attempt to ward off any vaccine side effects is to abstain from drinking the day leading up to your vaccine. As Dr. Cherian points out, drinking can lead to dehydration, which can exacerbate any side effects that do present themselves.

Two more things to keep in mind:

First, according to Dr. Cherian, you shouldn’t get your vaccine at the same time as other vaccines. “If you’ve already received another vaccine (the flu shot for example), you should wait at least 14 days before getting your COVID-19 vaccine,” he says. “Conversely, you should wait at least 14 days before getting any other vaccine after your COVID-19 vaccine.” This is because, according to the CDC, “data is lacking on the safety and efficacy of COVID-19 vaccines administered simultaneously with other vaccines.” However, the CDC also states that COVID-19 and other vaccines may be administered within a shorter period of time if “the benefits of vaccination are deemed to outweigh the potential unknown risks of vaccine coadministration.”

Lastly—and this comes from firsthand experience—you should avoid any Botox or filler appointments leading up to your vaccine. I’ve gotten my first dose of the Pfizer vaccine and one of the last questions they ask before injecting you is whether you’ve had any Botox or filler in the past 30 days. While having done so won’t nix you from being able to get the vaccine, it will (apparently) put you at a slightly higher risk of developing negative side effects. The nurse who administered my shot said that in a few national cases (so yes, it’s very rare, but still), folks who had had Botox or filler injections in the month leading up to their vaccine experience swelling in the region of the injectables.