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

People who have severely weakened or compromised immune systems are eligible to receive third doses of the Pfizer or Moderna vaccine as long as at least 28 days have passed since their second dose.

The CDC has also made Pfizer COVID-19 booster doses available under an Emergency Use Authorization (EUA) to anyone who:

• is age 65 years and older and residents in long-term care settings or, 
• is age 18-64 with certain underlying medical conditions, or, 
• is 18-64 and at increased risk of COVID-19 exposure and transmission due to institutional living setting or occupation, including healthcare workers, AND 
• received the 2-dose Pfizer vaccine at least 6-months ago.

Patients who do not have severely weakened or compromised immune systems and who received the Moderna or the Johnson & Johnson vaccines are not eligible for the booster shot at this time. If you are fully vaccinated (completed the primary series of the 2-dose Pfizer or Moderna vaccines, or the single dose Johnson and Johnson vaccine, you continue to have a strong level of protection against severe effects of COVID-19, including against the Delta variant. That protection is far greater than you had without the vaccine. 

If you would like to know more about the FDA and CDC’s recommendations about booster doses, visit the FDA or CDC. 

The FDA authorizes immunocompromised individuals to receive the third dose at least 28 days following the second dose of the same vaccine. If you are immunocompromised and received your second dose more than 28 days ago, you can get a third dose. If you are not immunocompromised, but you do meet the CDC’s qualifications for a booster shot, you can get a booster shot of Pfizer if you received your second shot of Pfizer at least 6-months ago. 

You can get the booster either at a Penn Medicine facility or at a local facility or pharmacy. Right now, Penn Medicine is providing third doses of the Pfizer COVID-19 vaccine to severely immunocompromised patients ages 16 and older and the Moderna COVID-19 vaccine to severely immunocompromised patients ages 18 and older.  In addition, we providing a limited amount of booster shots of the Pfizer vaccine to patients ages 65 and older who received their second dose of the Pfizer vaccine at least six months ago.

Currently, there is not data to support the use of an additional vaccine dose after a primary Johnson & Johnson vaccine in immunocompromised people. The FDA and CDC are working to provide guidance on this issue.

An antibody test is not necessary. It would not change the decision to give you an additional dose.

Based on preliminary studies, the side effects appear to be similar to the initial vaccine reactions, although they may be more pronounced. These include pain, redness and swelling at the injection site, as well as tiredness, headache, muscle pain, chills, fever and nausea. So far, there have not been serious side effects to additional dosing, but we will monitor patients closely.

Yes, please let your care team know if you get an additional dose of the vaccine, so we have an accurate report of your vaccination status in your health records.

Based on research, it is likely that COVID-19 vaccines will prevent people from getting and spreading the virus.

Both the Pfizer-BioNtech and Moderna vaccines are showing about 95 percent efficacy in their preliminary reviews. This means people who received these vaccines in clinical trials had a 95 percent lower risk of getting COVID than people in the trial’s control group who did not receive a vaccine. The Johnson & Johnson vaccine showed 72 percent efficacy in U.S. clinical trials.

The clinical trials showed that all three vaccines were 100 percent effective at preventing hospitalizations and deaths from COVID.

The research so far shows that the vaccines are 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 more than once. It is recommended that people who have had COVID 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, Moderna or Johnson & Johnson vaccines to give you COVID-19. None of the vaccines contain any live virus. Vaccines prime your immune system to recognize and fight off a disease, but they don’t actually cause an infection.

Learn about the types of COVID vaccines that are available or are in development

No, the COVID vaccines do not change or interact with your DNA in any way. The mRNA never goes into the nucleus – the part of the cell contains all of your own DNA and instructions – so it is impossible for it to alter your DNA.

Read more myths and facts about the COVID vaccine

The Moderna and Pfizer-BioNTech are mRNA vaccines that use tiny parts called messenger RNA (mRNA) carried in very tiny lipid particles. The Moderna and Pfizer-BioNTech 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, but each requires two doses.

The Johnson & Johnson vaccine is a vector vaccine, which places genetic material from the COVID-19 virus inside a weakened version of the adenovirus that cannot cause illness. Adenoviruses are very common viruses that usually cause colds. The Johnson & Johnson vaccine requires a single dose.

Learn more about the types of COVID vaccines that are available or are in development

The COVID 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.

The Johnson & Johnson COVID-19 vaccine is a vector vaccine. Vector vaccines use genetic material from the COVID-19 virus that is placed inside a weakened version of another virus, such as the virus that causes the common cold.

The weakened virus is then injected into your body, delivering information from the COVID virus. That information instructs your cells to copy the spike protein that is unique to COVID-19 and create antibodies against the virus.

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 COVID 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 pregnant, breastfeeding, or planning to become pregnant, you can receive the vaccine. The Society for Maternal-Fetal Medicine and other pregnancy experts recommend COVID-19 vaccination for pregnant and lactating people. Vaccination during pregnancy may help transfer protective antibodies to the baby through the placenta and breastmilk. These antibodies may lower the chance of the baby getting the COVID-19 disease.

Learn more about COVID and pregnancy

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

Recently, the CDC released new masking recommendations that state that fully vaccinated people no longer need to wear a mask or physically distance. However, CDC explicitly states that these new recommendations are NOT intended for healthcare settings. In all Penn Medicine locations, we require staff, patients and visitors to continue to wear masks, regardless of their vaccination status..

We recommend continuing to wear masks, wash hands, and socially distance as much as possible, even after getting the vaccine, to help bring the pandemic under control.