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What to Know About the COVID-19 Vaccine Side Effects

By Staff | January 21, 2021 | Cleveland Clinic

The COVID-19 vaccine is here and doses are beginning to roll out across the country and the world. It’ll take several months for inoculations to reach everyone based on current distribution plans but reactions to the vaccine will be followed closely, including side effects.

Having some side effects from receiving a vaccine isn’t unusual. For example, it’s not unusual for some people to experience mild side effects like headaches, muscle aches and soreness after receiving their annual flu shot.

Because of the speed with which it was developed and because it’s a new vaccine, though, some have expressed concerns about the COVID-19 vaccine, specifically its side effects. We talked to critical care specialist Rachel Scheraga, MD, about those side effects, what causes them and why the vaccine is safe.

The vaccines

Currently, two vaccines have been given the green light for distribution: one developed by Pfizer, in conjunction with BioNTech, and one developed by Moderna. Both were found to be about 95% effective during trials.

UPDATE: What You Need to Know About the Johnson & Johnson Vaccine

Neither vaccine has been fully approved by the Food and Drug Administration (FDA), which would allow the vaccines to be sold to hospitals and health care providers. But both have been approved for emergency use authorization (EUA) by the FDA because of the current state of emergency (the ongoing pandemic).

But it’s still important to keep in mind that we’re still in the early stages of the process. With those EUA come tons of data – data that will continue to be collected as doses are distributed – that prove these vaccines are both safe and effective. And that includes side effects of the vaccines.

What are the known side effects of the vaccines?

As with many vaccines, there are some side effects but, says Dr. Scheraga, those side effects are relatively mild.

“The side effects have mainly been arm soreness, fatigue, muscle aches, headaches and some instances of fever and chills,” she notes. She adds that between the two different vaccines the side effects are effectively the same.

She also says that the side effects are more commonly felt after the second dose rather than after the first. With the Pfizer/BioNTech vaccine, the second dose will come 21 days after the first while the second Moderna dose occurs 28 days later. “The data from the trials of the vaccines show that the side effects were more common after the second dose,” she says.

So far, no additional widespread side effects have become known but, again, it’s still early in the process, she points out. As these trials continue, the companies and health care providers will be on the lookout for anything else.

What causes these side effects?

According to Dr. Scheraga, the side effects have to do with how the COVID-19 vaccine works. Both the Pfizer/BioNTech and Moderna vaccines use the “messenger RNA” (or mRNA) approach. The strategy has been in development for years but this is the first time it’s been used in a distributed vaccine.

In this case, the harmless “spike” protein of the virus in the mRNA vaccine triggers the secretion of antibodies and recruitment of memory immune cells in the bloodstream that will allow for protection if one gets infected with the virus at a later time, Dr. Scheraga says.

“This activation of the immune system is what leads to some of these non-specific symptoms,” she adds.

Do the vaccine side effects mimic COVID-19 symptoms?

Dr. Scheraga notes that there are some overlapping features between the side effects and the symptoms of COVID-19. “Specifically, the fever and the muscle aches are some of the general side effects that mirror COVID-19 symptoms,” she says.

It’s important to keep an eye on the side effects you experience because, as she says, it’s possible that these symptoms could be a result of COVID-19. “It’s possible that if you contract the virus a few days before you receive your first dose, those symptoms could be indicative of COVID-19 infection instead of vaccine side effects.”

But, she adds, there are a few ways to tell if it’s just the side effects or something more serious. “Most times,” she says, “the side effects are mild and usually fade within 24 hours. You shouldn’t feel prolonged effects from the vaccine itself.”

Everyone’s reaction will be on a case-by-case basis, she says. “If you find those symptoms worsening or lingering longer than a day or two, you should contact your healthcare provider. They’ll be able to direct you on the best next steps, including, potentially, a COVID-19 test.”

No, you can’t get COVID-19 from the vaccine

“The COVID-19 vaccine will not give you COVID-19,” Dr. Scheraga says. “You’re just getting a sequence of the protein spike of the virus. You’re not getting either an active or inactive part of the virus.”

She adds, “You’re just getting what is needed from the virus so your immune cells can develop memory so that if you do contract COVID-19 after full vaccination, your immune system will be able to fight it off quickly so you don’t get sick.”

Are there any pre-existing medical conditions that could interfere with or intensify the side effects?

One question about the vaccine has been whether or not pregnant patients would experience any additional adverse reactions. So far, that’s unknown because, as Dr. Scheraga says, “The initial clinical trials didn’t include pregnant recipients so they’re still investigating whether or not they can safely receive the vaccine.”

Recent guidance developed by the Centers for Disease Control and Prevention (CDC) advises that if a pregnant patient is part of a group recommended to receive the vaccine, that patient would have the ultimate choice with the recommendation they consult their health care provider.

As with other vaccines, like a flu shot, the health care provider administering the vaccine will check with each recipient if they’ve experienced allergies with previous vaccines. Specifically, those reactions are generally caused by additives in the vaccine.

“Once you receive a dose, you’ll be monitored for 15 minutes which is typically enough time to see any indication of a severe allergic reaction,” Dr. Scheraga points out.

As of now, the CDC says that patients with a history of such reactions can receive the vaccine but they should have those incidents fully assessed by a health care provider to determine a fuller context around those incidents.

The CDC says, “These persons may still receive vaccination, but they should be counseled about the unknown risks of developing a severe allergic reaction and balance these risks against the benefits of vaccination.”

In those instances, the CDC calls for a post-vaccination observation period of 30 minutes instead of 15 minutes.

Are the vaccines safe?

Ultimately, the bottom line is that, yes, says Dr. Scheraga, the COVID-19 vaccines are safe. She explains the mRNA platform has been a big advance in technology that was developed and worked on prior to the pandemic.

“There’s a lot of concern because of the speed of development and it’s a brand new platform,” she says, “but it’s not brand new technology. This platform has been under development for this kind of real-time distribution for a while.”

A great deal of experimentation had already taken place, she notes, so that when the COVID-19 pandemic unfolded, it was a well-tested platform ready for implementation: “It’s safe, effective and potentially life-changing.”

This article is from Cleveland Clinic and was legally licensed through the Industry Dive publisher network. Please direct all licensing questions to legal@industrydive.com.

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