Frequently Asked Questions (FAQs) About the COVID-19 Vaccines

Based on research, it is likely that COVID-19 vaccines will prevent people from getting and spreading the virus. The research studies for the Moderna vaccine showed the vaccine prevented COVID-19 in about 95 out of 100 people and severe COVID-19 in 100 out of 100 people.  

The research so far shows that the vaccine is safe and effective.

We think that having COVID-19 may protect you from getting it again, but we are unsure how long. Some patients have had COVID-19 more than once.  It is recommended that people who have had COVID-19 still get the vaccine. 

It is too soon to know how long a vaccine will last. It is currently being researched.  Of the people who have received the vaccine, we know that they have been protected from COVID-19 for at least 4 months.

It is impossible for the Pfizer-BioNTech and Moderna vaccines to give you COVID-19. Neither vaccine contains any live virus.

Both vaccines use tiny parts called messenger RNA (mRNA) carried in very tiny lipid parts.  The two vaccines differ in the way the mRNA is built or the way the lipids are used. The two vaccines are also stored in different ways.

The COVID-19 vaccines prevent or lessen illness from the coronavirus. Both the Pfizer-BioNTech and Moderna vaccines have mRNA, which make the virus’ spike protein. This protein lets the virus attach to cells in our body. When we get the vaccine, we develop antibodies to the spike protein. This stops the virus from attaching to cells when exposed to the virus. Other parts of the body that prevent infection are made active by the vaccines to protect against future COVID-19 infection.

Vaccines for COVID-19 will start out being used under an Emergency Use Authorization (EUA) by the FDA. An EUA makes the vaccine available for public health emergencies. It means that the vaccine is available outside of a research study but is not yet approved. This is the usual first step for a new vaccine. The vaccine can continue to be used as long as people benefit from it. The research continues as it moves toward full approval.

The studies of vaccines included people ages 18 through 85 years old. It worked well for all ages. Studies are needed for people younger than 18 and pregnant women. More studies are going on or being planned. 

Yes, it is especially important for older adults to get the vaccine because they have the highest risk of being very sick or dying from COVID-19. 

Studies show that both vaccines are likely safe and will work for almost everyone. However, they cannot yet be used for children because those studies are not done.

If you are planning to become pregnant, you can receive the vaccine. The FDA also allows pregnant women to receive the vaccine. However, pregnant women were not studied in the vaccine trials, so there is not much information about the use of the vaccine among this group. If you are pregnant, we and the Society for Maternal-Fetal Medicine (SMFM) recommend that you discuss getting the vaccines with your provider. If you are breastfeeding, you can still get the vaccine and do not need to stop breastfeeding.

Yes, some people can get COVID-19 again. It is also not known how long someone is protected from getting the virus again.

Yes, you should continue wearing masks, handwashing, and social distancing after getting the vaccine. This will help bring the pandemic under control. 

We know that the great majority of people, even those with severe allergies, have tolerated the COVID-19 vaccine. People with allergies to environmental allergens (such as pollen), foods, latex, oral medications and stinging insects can receive the COVID-19 vaccine. The vaccine does not contain egg, gelatin or latex.

CDC recommends not to receive mRNA vaccine if you had a severe or immediate allergic reaction to any of the ingredients in the vaccine or anaphylaxis (a severe allergic reaction) to the first dose of the vaccine. If you have a history of an immediate allergic reaction to polyethylene glycol (also known as PEG), or to polysorbate, you should not receive the vaccine.

If you have questions about if you should receive the vaccine, please talk to your health care provider.

Polyethylene glycol (PEG) is a common ingredient in a wide variety of vaccines and FDA-approved medications. It is found in the colonoscopy preparation, Golytely, in the constipation treatment, MiraLax, as well as in IV medications such as PEGylated medications. It is also in a steroid injection, Depo Medrol (methylprednisolone acetate). Reactions to PEG are rare, but anaphylaxis has been reported. Polysorbate is not an ingredient in either mRNA COVID-19 vaccines, but it is closely related to PEG.

According to CDC guidelines, you may not be eligible to get the mRNA vaccine (or a second dose of the vaccine) if you have experienced any of the following allergic reactions.

• Severe allergic reaction (e.g., anaphylaxis) after a previous dose of an mRNA COVID-19 vaccine or any of its components
• Immediate allergic reaction of any severity to a previous dose of an mRNA COVID-19 vaccine or any of its components
• Immediate allergic reaction of any severity to polysorbate
• A history of an allergic reaction to an injectable medication

If you have experienced any of these reactions, please talk to your health care provider before getting a first or second dose of the vaccine.

If you decide to get the vaccine at a Penn Medicine vaccination site, you will be asked some questions about your allergy history before the vaccination. If you have had anaphylaxis (a severe allergic reaction) due to any cause, the vaccination team will decide if you need longer monitoring, or if you need to see your primary provider or allergy doctor before vaccination particularly if you report a history of an allergy to an injectable medication.

There are safeguards in place at Penn Medicine in case anyone experiences an allergic reaction to the vaccine. Everyone is monitored immediately after they receive the shot:

• At least 30 minutes for people who have a history of severe allergic reactions
• At least 15 minutes for all other individuals

We have a virtual urgent care service, called Penn Medicine OnDemand, which you can use as a resource at any time if you develop a reaction that concerns you.

If you received the COVID-19 vaccine and developed a reaction within 4 hours of being vaccinated, you should call Penn Medicine OnDemand at 215-615-2222. Not all reactions are truly allergic reactions; a provider will first get information about your reaction and decide how to best manage it.

If you have severe symptoms with wheezing, throat tightness, nausea and hives, seek emergency care.

It is common to experience a reaction (or, side effect that is not considered allergic) to the vaccine. Side effects include fever, chills, muscle aches, headache and soreness at the injection site. These symptoms commonly begin happening at any time point after receiving the shot and typically last 2 to 3 days. If symptoms persist longer or you develop a high fever, please call Penn Medicine OnDemand.