Is the COVID-19 vaccine safe?


by Tresa McNeal, MD, FACP, SFHM

Jan 5, 2021

Updated March 3, 2021

As the COVID-19 vaccines are being distributed, it’s normal to have questions. Getting the vaccine is the best way to protect yourself and your loved ones and help stop the spread of the coronavirus. But, as with any medical decision, it is important that you feel confident making an informed decision for your health.

So, let’s talk vaccine safety…

How were the COVID-19 vaccines studied?

The first vaccine approved for use by the Food and Drug Administration (FDA) was the Pfizer vaccine. We know that it was studied in close to 44,000 different people with around 21,000 people getting the active vaccine compared to others who received a placebo. The Moderna vaccine was similarly studied in more than 30,000 people with around 15,000 getting the active vaccine. The Johnson and Johnson vaccine was studied in about 40,000 people.

These types of studies are monitored by an independent review board. For approval, the vaccine also has to be reviewed by the Centers for Disease Control and Prevention (CDC) and FDA before being approved.

At Baylor Scott & White, we have also had our own task force working on the vaccines. Side effects from the vaccine were similar among vaccine recipients and those who got placebo. Also, keep in mind that while these vaccines were developed quickly, the science behind the vaccine has been extensively studied for more than a decade.

Is the COVID-19 vaccine a live vaccine?

None of the COVID-19 vaccines currently in development in the U.S. use the live virus that causes COVID-19. The goal for each of them is to teach our immune systems how to recognize and fight the virus that causes COVID-19. The belief that the vaccine can actually give you the virus is a myth. Learn more about how COVID-19 vaccines work.

Are there any side effects?

As with any vaccine, there are a few side effects to be aware of. The most commonly reported side effect is soreness at the injection site similar to other vaccines you have received for the flu or measles. Mild fatigue, chills or headache may also occur.

Remember, sides effects can occur with any vaccine — and are a positive sign that your body is building immunity against the virus. Any side effects that you experience should go away in a few days. Side effects may be stronger after the second dose of the vaccine.

How does an mRNA vaccine work?

You’ve likely heard a lot of talk about mRNA lately, but what is it? mRNA is just a small fragment of RNA that tells your cell to make a portion of the spike protein of the COVID-19 virus. Once the cell makes this tiny portion of the virus, your own body’s immune system sees this and recognizes it as something that it needs to learn to fight.

And that’s the point of the vaccine — to help your body make antibodies that learn to fight this small portion of the virus without getting truly sick. Then, when you do encounter COVID-19 and it tries to infect you, your body will be quick to respond with its own lifesaving antibodies. Both the Pfizer and Moderna vaccines are mRNA vaccines.

How do viral vector vaccines work?

While the Pfizer and Moderna vaccines are mRNA vaccines, the Johnson & Johnson vaccine is a viral vector vaccine.

“Viral vector vaccines use a modified version of a different virus (the vector) to deliver important instructions to our cells. For COVID-19 viral vector vaccines, the vector (not the virus that causes COVID-19, but a different, harmless virus) will enter a cell in our body and then use the cell’s machinery to produce a harmless piece of the virus that causes COVID-19. This piece is known as a spike protein and it is only found on the surface of the virus that causes COVID-19. The cell displays the spike protein on its surface, and our immune system recognizes it doesn’t belong there. This triggers our immune system to begin producing antibodies and activating other immune cells to fight off what it thinks is an infection.”

CDC: Understanding Viral Vector COVID-19 Vaccines

Are the COVID-19 vaccines effective?

Yes, these vaccines have proven effective against the COVID-19 virus. After one dose of the Pfizer vaccine, you are able to prevent 50 percent of infections that you may encounter due to COVID-19. After two doses, that effectiveness jumps to 95 percent. The Moderna vaccine has proven 94 percent effective at preventing COVID-19 illness in people who received two doses who had no evidence of being previously infected. The Johnson & Johnson vaccine has proven 72 percent effective at preventing overall COVID-19 illness in the U.S. but 86 percent effective at preventing serious COVID-19 illness, hospitalization and death.

What about long-term side effects?

While it is too early to know the full extent of long-term side effects, the vaccine study followed participants for two months and documented symptoms. Any symptoms reported were similar in both the vaccine recipients and the placebo groups. Keep in mind that while these specific vaccines is new because this is a new version of coronavirus, the technology behind them has been studied for more than 10 years. So, you can feel confident knowing that this vaccine is backed by years of scientific research.

Who should not get the vaccine?

Right now, the Pfizer vaccine is approved for people over 16 years of age. The Moderna and Johnson & Johnson vaccines are approved for people over 18 years of age. If you are actively infected with COVID-19, you should wait until you recover and then get the vaccine because it helps you learn how to fight the virus more reliably. If you had COVID-19 and were hospitalized and received either convalescent plasma or monoclonal antibodies, you should wait 90 days to receive the vaccine. Keep in mind that these recommendations are subject to change.

Can you get the vaccine if you are pregnant or breastfeeding?

The American College of Gynecology (ACOG) has recommended that the vaccine not be withheld from pregnant and nursing women, particularly if they are in a high-risk group. The best advice is to talk to your own doctor about your personal health situation to determine what is best for you. Refer to the ACOG for updates. Learn more about vaccines during pregnancy here.

How long will it take to get back to normal?

We must remember that getting a large portion of the population vaccinated takes time. During this time, we all still need to wear masks and continue other safety measures even if we are immunized — we don’t yet know whether a vaccinated person could be exposed to the virus and still spread it to others while in the process of fighting it. That’s why it is best to look at the vaccine as another layer of personal protective equipment and continue all the other safeguards for now. We must keep learning, immunizing and caring for each other as we get life back to normal.

To learn more about the COVID-19 vaccine, visit

Please note: Due to the fluid nature of the COVID-19 vaccine situation, information may change frequently — please refer to the Centers for Disease Control and Prevention (CDC) and Texas Department of State Health Services (or your local state authorities) for the most up-to-date vaccine information.

About the Author

Tresa McNeal, MD, FACP, SFHM, is an internal medicine physician on the medical staff at Baylor Scott & White Medical Center — Temple.

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