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What to Expect When it Comes to COVID-19 Vaccine Side Effects

By June 29, 2021October 23rd, 2023Expert Advice Featured Well-being
Person with "I got my COVID-19 vaccine" sticker.

If you have an upcoming COVID-19 vaccine appointment you may be wondering how you’ll feel after you get the vaccine. You’ve probably read about or heard other people talk about side effects, but you’re not sure what to expect. Your cousin felt completely fine after his shot, your friend had a sore arm and a headache, and your colleague was in bed with a fever and body aches.

Immune response varies from person to person and depends on a variety of factors (including medical history, type of vaccine, age, gender, body mass, and previous immunity), but the most commonly reported side effects include:

  • Tiredness
  • Headache
  • Muscle pain
  • Chills
  • Fever
  • Nausea
  • Pain, redness, and swelling (at the injection site)

Luckily, side effects are usually mild and short-lived, with most people reporting that side effects subsided in less than 48 hours.

How to Reduce Your Discomfort

The good news is there are things you can do to help reduce your discomfort after getting your shot:

  • Drink plenty of fluids.
  • Rest.

And while you should avoid taking an over-the-counter painkiller before getting the COVID-19 vaccine (unless you take them routinely for a medical condition), it’s okay to take Tylenol after the vaccine to relieve symptoms. (Ibuprofen and other painkillers that target inflammation could potentially curb the immune response, which is why doctors recommend sticking with Tylenol.)

Why Do We Experience Side Effects?

If the vaccine is working to protect us, why do we get symptoms that make it seem like we’re sick? According to the CDC, “COVID-19 vaccines teach our immune systems how to recognize and fight the virus that causes COVID-19. Sometimes this process can cause symptoms, such as a fever. These symptoms are normal and are signs that the body is building protection against the virus that causes COVID-19.”

Possible outcomes

Side effects after second dose: You may experience more intense side effects after your second shot than you did after your first shot. This is the most commonly reported reaction, with more people reporting side effects after the second dose of the Pfizer or Moderna vaccine than after the first dose.

After the first shot of the vaccine, your cells start producing a harmless protein called the “spike protein.” Your immune system recognizes the protein as something foreign and starts responding by making antibodies against this “invader.”

After your second dose, your cells recognize the spike protein from the first dose, and launch an even stronger response. This response can lead to the common side effects of fever, aches, headaches, etc. The good news is this means your body is creating more antibodies, which is more beneficial to you. And luckily, the side effects are short-lived.

Side effects after first dose: There’s a lot of buzz around the side effects after the second vaccine dose, but what about the smaller number of people who experience a strong reaction after their first vaccine dose? What does this mean? There are some studies indicating that if you experience a strong reaction to the first dose of a COVID-19 vaccine, it may be a sign that you had a previous COVID-19 infection (even if you weren’t aware of it).

No side effects: So, what if you’re one of the lucky ones that feels fine after getting each dose? Does that mean the vaccine isn’t working? Not so, say experts. Just because you didn’t have any side effects doesn’t mean it isn’t working. Your immune system doesn’t always cause physical side effects when it’s working to protect you.

Separating Fact from Fiction

There’s a lot of misinformation that has been spread about the vaccine, but it’s important to stick to the facts.

Myth: You can get COVID-19 from the vaccine.
Fact: It’s important to note that just like with the flu vaccine, when you receive the COVID-19 vaccine you are not getting the live virus. According to the CDC, “None of the authorized and recommended COVID-19 vaccines or COVID-19 vaccines currently in development in the United States contain the live virus that causes COVID-19. This means that a COVID-19 vaccine cannot make you sick with COVID-19.”

For those who get COVID-19 after their first vaccine dose, that may be because they had already been exposed to COVID-19 at the time their body was still creating immunity.

Myth: The vaccine causes abnormal periods, reproductive harm, or impacts fertility.
Fact: There is no data linking COVID vaccines to a decrease in fertility and there is no evidence that the vaccine causes any reproductive harm.

In fact, there are benefits to getting the vaccine when pregnant or breastfeeding, including the fact that pregnant and nursing mothers who get the vaccine pass along antibodies to their child in utero or via breastmilk.

Myth: The vaccine causes blood clots.
Fact: While the Johnson & Johnson vaccine was temporarily paused after a small number of blood clots were reported, the CDC and FDA completed a thorough investigation of the cases and recommended that administration of the Johnson & Johnson vaccine resume since the vaccine’s “known and potential benefits outweigh its known and potential risks.”

And while the rare adverse reaction can be concerning, it’s important to keep everything in perspective. Nothing in life is without risk — driving a car, smoking, taking birth control pills, even taking vitamins or Tylenol — all of these actions carry some level of risk. But from a risk assessment standpoint, statistically, you are much more likely to have serious health problems if you get COVID-19 than if you get the vaccine.

Don’t Forget Your Second Shot!

So, if you made it through your first appointment and received a Pfizer or Moderna vaccine, congrats! You’re halfway there. Remember, you’re not fully protected until two weeks after your second shot, so don’t forget that second dose!


If you still have questions about the COVID-19 vaccine, there are reliable and trusted resources that you can count on to provide unbiased facts.

Dr. Dolores Roman

Dr. Dolores Roman joined Independence Blue Cross in 2019. As a 20-year veteran of emergency rooms in and around the Philadelphia area, Dr. Roman has dealt with every kind of emergency. Now as a medical director at Independence, Dr. Roman is involved in utilization management, case management, and quality improvement. What Dr. Roman loves most about this job is the opportunity to collaborate with colleagues in order to enhance the health and well-being of those served by Independence Blue Cross.