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

COVID-19 Vaccine Prevention and Safety

Will a vaccine prevent COVID-19?

Yes.  The COVID-19 vaccines work by teaching your immune system how to recognize and fight the virus that causes COVID-19.  This helps protect you from getting sick with COVID-19.

How do we know that the COVID-19 vaccines are safe and effective?

The U.S. vaccine safety system ensures that all vaccines are as safe as possible. The COVID-19 vaccines that are available in the U.S. have been tested in research studies with many thousands of people. These studies have shown that the vaccines are safe and effective.

How long will a vaccine protect people?

It is too soon to know how long a vaccine will last. We do not know yet if people will need to get the vaccine one time, every once in a while, or every year like a flu shot. It is currently being researched. 

COVID-19 Vaccine Development

What are the differences 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. Learn more about the types of vaccines available.

What ingredients are in the COVID-19 vaccines?

  • The full ingredient list for the Pfizer vaccine is available here on page 2
  • The full ingredient list for the Moderna vaccine is available here on page 2
  • The full ingredient list for the Johnson & Johnson (Janssen) vaccine is available here on page 2

How do mRNA vaccines work?

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.

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..

Will the mRNA vaccine alter my 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.

Getting Vaccinated

Who should get the vaccine?

The Pfizer vaccine is approved for people 12 years and older, and Moderna and Johnson & Johnson vaccines are approved for 18 and older.

These people can get the vaccine, but they should talk to their doctor first:

  • People with a history of severe allergy to any vaccine or injectable medication
  • People who are pregnant or breastfeeding
  • People with immune-compromising or autoimmune conditions
  • People on blood thinners.

If you have any questions about your health and the risks or benefits of the vaccine, please ask your healthcare provider before you schedule your vaccine appointment.

Who should not get the vaccine?

These people should not get the COVID-19 vaccine:

  • Anyone with a severe allergy to any ingredients in the mRNA vaccines.
  • Those younger than 12 years of age.
  • People currently isolating or experiencing symptoms of COVID-19. These people can get vaccinated after they have finished isolation.

If you have any concerns about a health condition, please ask your healthcare provider before you schedule your vaccine appointment.

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. 

Can pregnant and breastfeeding women get the COVID-19 mRNA vaccine?

Yes. The Society for Maternal Fetal Medicine, the CDC, and the American College of Obstetricians and Gynecologists (ACOG) have said that pregnant women may be vaccinated if they choose to do so. If you are pregnant or breastfeeding, please discuss the vaccine with your doctor. Pregnant women were not included in the early COVID-19 vaccine studies, but a few participants became pregnant during the studies. As a result, we only have a small amount of data regarding the safety of these vaccines in pregnant women.

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

Yes, you should get vaccinated. Some people can get COVID-19 again, and we do not know how long someone is protected from getting the virus again.

If you were treated for COVID-19 symptoms with monoclonal antibodies or convalescent plasma, you should wait 90 days before getting a COVID-19 vaccine. Talk to your doctor if you are unsure what treatments you received or if you have more questions about getting a COVID-19 vaccine.

Can I get other vaccines while I get the COVID vaccine?

No. You should not get any other vaccines for 14 days before and after you get the COVID vaccine.

What are the side effects of the vaccine?

The most common side effects of the vaccine are pain at the site of the shot, tiredness, headache, muscle aches, chills, joint pain, and fever.  These side effects are more common after the second dose and may last a few days.


The risk of a serious reaction to the COVID-19 vaccine is very low.  The CDC and FDA are closely monitoring the safety of all approved vaccines. As of early January, cases of anaphylaxis (a serious allergic reaction) were occurring about 5.5 times for every 1 million COVID-19 vaccine doses.


The risk of COVID-19 is much greater than the risk of a serious reaction from the vaccine. As of January 18, there have been 1,515 COVID-19 deaths for every 1 million people in Pennsylvania.

Can someone get COVID-19 from the vaccines?

No.  It is not possible to get COVID-19 from the vaccines because they do not contain the live virus that causes COVID-19.


Should I wait to schedule a screening mammogram following my vaccination?

The COVID-19 vaccines can cause swollen lymph nodes after the vaccine is administered. This is a natural response and means your immune system is doing its job. However, the enlarged lymph nodes can show up in a screening mammogram leading to a false positive or confusing result, requiring additional and unnecessary diagnostic testing. Therefore, we recommend you schedule your screening mammogram either before receiving your first dose of the COVID-19 vaccine or 4 weeks after your second (final) dose. If you would like to reschedule your screening mammogram, please call Centralized Scheduling at 717-544-5941.


Is it OK to take pain medication before and after getting the COVID-19 vaccine?

You may have some side effects after getting a COVID-19 vaccine. Pain on the arm where you got the shot, fever, chills, tiredness, and headache are normal signs that your body is building protection.

The CDC says you can take over-the-counter pain medicine, such as ibuprofen (like Advil), aspirin, antihistamines, or acetaminophen (like Tylenol) to relieve these symptoms. Taking pain medication ahead of your shot to try and decrease symptoms is not recommended because it is not clear if it could affect the vaccine’s effectiveness. As with any medication, the CDC recommends talking to your doctor first. Learn more on the CDC website.

COVID-19 Vaccine and Allergies

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-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 primary 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 mRNA COVID-19 vaccines, but it is closely related to PEG.

Who may not be eligible or may need further evaluation for the mRNA COVID-19 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 primary care provider before getting a first or second dose of the vaccine.

If I have allergies, what happens when I receive the COVID-19 vaccine?

If you decide to get the vaccine at a Penn Medicine Lancaster General Health 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 Lancaster General Health 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 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-19 vaccine and developed a reaction within 4 hours of being vaccinated, you should call Penn Medicine OnDemand at 717-544-2222. 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.

After Getting the Vaccine

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

At this time, fully vaccinated people can gather indoors without physical distancing or wearing masks with:

  • Other people who are fully vaccinated
  • Unvaccinated people from one other household, unless any of those people or anyone they live with has an increased risk for severe illness from COVID-19

Until more is known, fully vaccinated people should continue to wear masks and stay 6 feet apart from other people in public or when visiting with unvaccinated people from multiple households or unvaccinated people who are at higher risk for severe COVID-19.

Workplaces and schools may also have special policies and procedures for safety. Check with your employer or school if you have questions about their policies.

If I complete the vaccine series, will I still need to quarantine?

  • If you were in close contact with someone who has COVID-19, you do not have to quarantine if:
  • You have completed the second dose in a 2-dose series or one dose of a single-dose vaccine
  • It has been at least 2 weeks since your last vaccine dose
  • Your last dose in the vaccine series was within the past 3 months
  • You do not have COVID-19 symptoms
  • If you travel out of state, you should follow state guidance about quarantine during or after travel.

Can I still spread the virus to others even if I am vaccinated?

We do not know yet whether vaccinated people can still be carriers of the virus and if they can pass it to others. The safest thing to do while everyone is still getting vaccinated is to continue to practice physical distancing and wearing a mask in all encounters with people outside of your immediate household.

What do I do if I get COVID -19 between my first and second doses?

You should still get the second dose of the vaccine if your symptoms have resolved and your quarantine has ended. If you were treated for COVID-19 with monoclonal antibodies or convalescent plasma, you should wait 90 days before getting a COVID-19 vaccine.

How soon will the vaccine start to work?

The body needs time to create the cells that help fight the virus. This usually takes a few weeks (at least 10 days to 2 weeks after your vaccine, based on the research that is currently available).

Vaccine Availability and Distribution

When will the COVID-19 vaccine be available?

The vaccine is available to all in the community that meet the eligibility requirements.  Please check for options to get the vaccine. 

Will the COVID-19 vaccine be mandatory?

The COVID-19 vaccine is not mandatory.

How is LG Health helping to get the vaccine to everyone who wants it?

The vaccine is available to all in the community that meet the eligibility requirements.  Please check for options to get the vaccine. 

Is there a cost for the vaccine?

Vaccines are provided free of charge.

Facts about the COVID-19 Vaccine

Information about the vaccine is available in many languages at the PA Department of Health website. Click “Translate” in the upper right corner to choose your language.

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