Dr. Meghan Lane-Fall explaining the vaccine consent form to female patient at the West Philly community vaccine clinic

Get the answers to common questions about the COVID-19 vaccines, including vaccine safety, who made the COVID vaccine, who should get the vaccine and when the vaccine will be available. 

Booster Shots (Third Dose of mRNA Vaccines)

Who can or should get an additional dose of the COVID-19 vaccine ("booster shot")?

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

How soon should I get the booster? How long should I wait after my second dose?

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. 

Where should I get the booster?

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.

Can I get a booster if I'm immunocompromised and got the Johnson & Johnson COVID-19 vaccine?

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.

Should I have antibody test before I get the booster?

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

What kind of side effects should I anticipate if I get an additional dose of vaccine?

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.

Should I let my care team know if I get the booster outside of Penn Medicine?

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.

COVID-19 Vaccine Prevention and Safety

Will a vaccine prevent COVID?

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.

How will we know if the COVID vaccines are safe and effective?

The research so far shows that the vaccines are safe and effective.

Is it possible to achieve immunity without a vaccine?

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.

How long will a vaccine protect people?

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.

Can someone get COVID from the vaccines?

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.

Can the COVID vaccine alter your DNA?

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.

COVID-19 Vaccine Development

What is the difference among the Pfizer-BioNTech, Moderna and Johnson & Johnson vaccines?

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.

How do mRNA vaccines work?

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.

How do vector vaccines work?

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.

Are these vaccines fully approved by the FDA for use?

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.

Getting Vaccinated

Who does the COVID vaccine protect?

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. 

Should older adults get the vaccine?

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. 

Who is the vaccine good for?

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.

What if I am pregnant or breastfeeding, or plan to become pregnant?

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

If I already had COVID-19, should I still get the COVID vaccine?

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

If I complete the vaccine series, will I still need to wear a mask and social distance?

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. 

Can I choose which vaccine to get?

At this time, our supply of COVID-19 vaccine doses is limited, so we will offer you whichever vaccine we have available at the time of your appointment. It is not possible to choose one vaccine over another.

If you receive an mRNA vaccine (Moderna or Pfizer-BioNTech) that is delivered in two doses, your second dose will need to be from the same manufacturer as your first dose.

The Moderna, Pfizer-BioNTech and Johnson & Johnson vaccines all were 100 percent effective at preventing hospitalizations and deaths from COVID-19 during clinical trials.

Can I get other vaccines, like the flu shot, at the same time as a COVID-19 vaccine?

Yes, it is safe for you to receive a COVID-19 vaccine at the same time as another vaccine, such as a flu shot. You do not need to space out or wait a period of time between receiving a COVID vaccine and your flu shot. The COVID vaccine and the other vaccine will be just as effective if you receive them at the same time as they will at different times.

Additionally, if you had COVID-19, you do not need to wait before getting a flu shot.

Allergies and Reactions to the COVID-19 Vaccine

Is the vaccine safe for me if I have allergies?

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

CDC recommends not to receive a COVID 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 an mRNA 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.

What is polyethylene glycol?

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 of the mRNA COVID-19 vaccines (Pfizer and Moderna), but it is closely related to PEG. The Johnson & Johnson vaccine contains polysorbate.

Who may not be eligible or may need further evaluation for the mRNA COVID vaccine?

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 I have allergies, what happens when I receive the COVID 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

What should I do if I had an allergic reaction to the first mRNA vaccine shot?

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 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.

What should I do if I have an unusual reaction to the Johnson & Johnson vaccine?

It is common for people to have mild symptoms – such as tiredness, headache, muscle pain, chills, fever, nausea, and redness or soreness around the injection site – between 24 and 48 hours after receiving the Johnson & Johnson COVID vaccine.

If you recently received the J&J vaccine, you will most likely not experience any serious, adverse effects. If you develop severe headache, abdominal pain, leg pain or shortness of breath within three weeks of being vaccinated with the J&J vaccine, you should contact your doctor immediately or go to the nearest hospital emergency department. Make sure you tell the health care provider that you received the J&J vaccine.

Health care providers are asked to report adverse events to the Vaccine Adverse Event Reporting System

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