What to expect when getting the COVID-19 vaccine, and how to handle the side effects

If you’re one of the millions of Americans who haven’t gotten the COVID-19 vaccine yet, you may be wondering what to expect from the whole process, including:

  • What side effects are normal?
  • What side effects aren’t normal?
  • Is there anything I can take to make the side effects better?

There’s a lot of information out there that may have conflicting answers to these questions, so our pharmacists have put together a guide to help break down some of the mystery surrounding the COVID-19 vaccine process. 

Normal reactions to the COVID-19 vaccines

We’d recommend going into your vaccination appointment expecting to feel some side effects afterward. These are completely normal and aren’t a cause for concern. Nearly all participants (91.6%) in the vaccine clinical trials experienced injection site pain and swelling, but other common side effects included: 

  • Fatigue (68.5%)
  • Headache (63%)
  • Muscle pain (59.6%)
  • Chills (43.4%)

Fever and nausea have also been reported. 

The good news is that these side effects mean the vaccine is working! The two vaccines currently approved in the U.S.—one from Pfizer-BioNTech and one from Moderna—are “reactogenic.” This means that they cause an immune response, which then results in side effects. 

To break it down further, your body has certain defense mechanisms it uses when it feels under attack—which is pretty much any time it encounters a foreign particle (such as a new virus). When the vaccine is injected into your arm, your body registers it as an attack because it’s never encountered it before. So, it activates some of its defense mechanisms. 

One of those defenses involves raising body temperature, or in other words, a fever. This is because many foreign particles (such as viruses) are fragile at higher temperatures, so this is an attempt by your body to make itself an inhospitable environment. That’s why you might experience a fever when you get the vaccine.

Another method of “fighting back” from your body is to activate your immune cells. Their job is to start memorizing and creating antibodies that attack the foreign particles. This is why you might feel fatigued after the COVID-19 vaccine since your body is kicking into gear to make a huge production of these antibodies. 

It’s important to note that just because you feel sick (and the symptoms might be similar to the ones caused by COVID-19), that doesn’t mean you have COVID-19. The vaccine does not actually contain COVID-19, and it cannot give it to you. You might separately contract COVID-19 (especially if you’ve only received one vaccination dose, as it takes two to get the full benefit), but the cause would not have been from the vaccine. That’s why medical experts still recommend taking safety precautions like wearing a mask, physical distancing, and handwashing even after you’ve been vaccinated. 

(If you have more questions about how the vaccine works, you can read our guide here). 

If you don’t experience any side effects, that isn’t a cause for concern either! The vaccine is still working for you. In fact, side effects were less common for anyone age 55 and above in the vaccine trials. This is because younger people have more active immune systems, so the vaccines tend to produce a bigger response and hence, more side effects. Scientists have also noticed a pattern of more people experiencing side effects after the 2nd dose of the vaccine. This is because your immune system is triggering an even greater immune response to solidify its response to the virus. 

Lastly, it may ease any lingering anxiety further to know that this is not a new phenomenon. Other vaccines besides the COVID-19 ones cause side effects as well. For example, the seasonal flu shot has been known to cause fever and fatigue, while the shingles vaccine can cause shivering, muscle pain, and stomach upset.

Abnormal reactions to COVID-19 vaccines

In most cases, the side effects will resolve within a few days. However, there are a few cases you should watch out for side effects that don’t go away after 2 days. Normal side effects typically should resolve within 1 – 2 days. If that happens to you, reach out to your doctor. 

It is also possible, but very rare, to have a serious allergic reaction (also known as “anaphylaxis”)  right after you receive the vaccine. From December 14 to 23, 2020, of the roughly 1.8 million people who received their first dose of Pfizer-BioNTech vaccine in the U.S., only 21 had a severe allergic reaction. 

If a severe allergic reaction is going to occur, it’ll likely be within 15 to 30 minutes of receiving the vaccine. Signs of anaphylaxis include: 

  • Shortness of breath
  • Wheezing
  • Dizziness
  • Hives
  • Swelling of the face

These reactions do require immediate medical attention, which is why trained professionals at vaccination sites will monitor you for 15 minutes after injection, or 30 minutes if you have a history of anaphylaxis. 

Managing side effects of the COVID-19 vaccines

There are a few tips for dealing with the side effects if you do end up feeling them. For the injection site, the CDC recommends:

  • Applying a cool, clean, wet washcloth
  • Gently rotate your arm in circles and do light exercise

Doing these will help increase blood flow to the site, which will reduce any tenderness and swelling you might feel. 

As for the other side effects (fever, chills, fatigue, aches, etc.), you might think to reach for over-the-counter fever and pain relievers, such as acetaminophen (Tylenol)  or ibuprofen (Advil, Motrin). However, there has been a lot of inconclusive research about whether or not these drugs might affect how well the vaccine works. 

A study conducted by Duke University in 2016 found that the effectiveness of various vaccines dwindled when children took fever and pain relievers before their scheduled vaccines and not as many antibodies were produced. Overall, medical experts advise against taking acetaminophen or ibuprofen before receiving the vaccine. While it might sound like a good idea to try to get ahead of any possible side effects, taking these drugs preemptively might hamper the vaccine’s ability to work. 

As far as taking pain relievers after receiving the vaccine, there is more conflicting guidance. Participants in both the Moderna and Pfizer-BioNTech trials were not prohibited from taking over-the-counter (OTC) fever and pain relievers after receiving their vaccination doses, and the results from both studies still showed the vaccine working at high rates of 94 to 95%. 

However, a study published in the Journal of Virology in January found that NSAIDs (nonsteroidal anti-inflammatory drugs) might cut down on antibody production and dampen your body’s immune response to the virus. The authors of the study are now theorizing that these OTC pain and fever relievers may potentially affect the immune response to the COVID-19 vaccines. However, more studies need to be conducted to determine the definite relationship. 

Given this, at this time our pharmacists recommend taking a conservative approach and avoiding pain relievers if you can. However, if you do need to take one to manage side effects, we’d recommend acetaminophen instead of a NSAID like ibuprofen based on the findings of the Journal of Virology. 

Keep in mind that the research on this is continually changing, so these guidelines are likely to be updated in the future.

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