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  • May 13, 2021
  • 68°

Penn State Health doctors answer your questions about the COVID-19 vaccine

Presented by Penn State Health

  • 3 min to read
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Dr. Stephen Henderson with Penn State Health Cocoa Outpatient Center puts a bandage on Lynn Davis from Cleona after giving her a COVID-19 vaccination.

By now, everyone has seen countless images of people receiving the COVID-19 vaccine. But many people still have questions.

Dr. M. Fahad Khalid, chief of the Division of Hospital Medicine at Penn State Health Milton S. Hershey Medical Center, and Dr. Mohammad Ali, an infectious diseases physician at Penn State Health Holy Spirit Medical Center, say while the vaccine doesn’t contain any live COVID-19 virus, it teaches the human immune system to protect against it.

Both vaccines that received Emergency Use Authorization from the U.S. Food and Drug Administration (FDA)—the Pfizer-BioNTech and Moderna vaccines—are messenger RNA (mRNA) vaccines. They are not live viruses, which means the vaccine does not actually give you COVID-19. Instead, they work by carrying a message to your cells to make a spike protein. The spike protein the vaccines create is the same one found on the surface of the virus that causes COVID-19.

This harmless spike protein is then displayed on the cell surface, where your immune system sees it. Your immune system knows it doesn’t belong there, so it begins to make antibodies to fight the virus. When the process is complete, your body knows how to protect itself from future COVID-19 infections. While mRNA is a type of genetic code, it never enters the center (nucleus) of your cells. “That means it never converts into DNA,” Khalid said. “The mRNA itself is destroyed by the cells after they produce the spike protein.”

“The spike protein itself cannot cause an infection,” Ali said.

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mRNA vaccines prompt cells to make a spike protein, like those found on the surface of the COVID-19 virus.

Here, Khalid and Ali answer many common questions people have about both vaccines:

Why should I get a COVID-19 vaccine? In ongoing clinical trials, both the Pfizer-BioNTech  and Moderna COVID-19 vaccines have been shown to prevent COVID-19 following two doses. They may also prevent hospitalizations and death from COVID-19, but this is still being studied. “Their effectiveness is tremendous,” Ali said. “The seasonal flu vaccine is typically 40% to 60% effective, and the COVID-19 vaccines are 94% to 95% effective.”

The vaccines were approved quickly. Are they safe? Keep in mind that scientists had already been developing vaccines for other coronaviruses, like SARS and MERS, but stopped when they weren’t needed. This paved the way for pharmaceutical companies to use advances in vaccine research and production to create vaccines in months. However, both vaccines still followed rigorous FDA guidelines, including the normal regimen of clinical trials and Phase 1, 2 and 3 trials. 

Do people get severe allergic reactions to the vaccine? The Centers for Disease Control and Prevention (CDC) reports a limited number of cases where people experienced a severe allergic reaction (anaphylaxis) or reaction such as hives, swelling or wheezing. The CDC does not recommend the vaccine for people who had a prior severe allergic reaction to any ingredient in the COVID-19 vaccine. People who have had allergic reactions to other vaccines should ask their doctor about taking the COVID-19 vaccine. People with non-vaccine-related allergies—food allergies, pet allergies, seasonal allergies—are safe to get vaccinated, says the CDC.

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Kelsey Overfield, a pharmacist with Penn State Health St. Joseph Medical Center, prepares to give the first COVID-19 vaccination to a staff member in December 2020.

Will the vaccine side effects be worse than getting COVID-19? You may experience some swelling or pain at the injection site. Some people report fever, chills, headache or muscle pain after the second shot. These side effects are temporary and not as severe as actually having COVID-19. They also mean your immune system is working to create antibodies.

Do I need a vaccine if I already had COVID-19? Yes. Currently, the CDC recommends vaccination even in people who have had COVID-19 in the past. This is because we do not know how long immunity to the virus lasts after someone is infected.

Do I need to wear a mask after getting the COVID-19 vaccine? Yes, you must continue to wear a mask, practice social distancing and wash your hands frequently. The vaccine protects you from getting sick with COVID-19, but researchers still don’t know if individuals can still get infected and transmit the virus to others.

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How are vaccinations being prioritized? The Pennsylvania Department of Health (DOH) has established four phases for distribution, which can be found on the DOH website. Pennsylvania is currently in Phase 1A, for those who are most at risk. You can also get up-to-date information on COVID-19 at

What should I do before and after my vaccine? Currently, the CDC is not recommending that you take an over-the-counter (OTC) medicine, such as aspirin, ibuprofen, acetaminophen or antihistamines, to prevent side effects before getting the vaccine. It is not yet known if these medications can affect how well the vaccine works. If you have pain or other side effects after getting the vaccine, talk to your doctor about whether it is OK for you to take OTC medications.

More vaccines may be approved soon. Can I choose which one I get? You should get the first vaccine you can register for because all approved vaccines will give you protection against COVID-19. “The sooner people get vaccinated, the sooner we can begin to put this pandemic behind us,” said Dr. Peter Dillon, chief clinical officer of Penn State Health.

For more information about Penn State Health, please visit

Presented by Penn State Health

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