Vaccines: Frequently Asked Questions

New medicines and vaccines may bring hope but they also bring lots of questions.

In this section:


Vaccine Basics & Info

Stopping a pandemic requires using all the tools available. Vaccines work with your immune system so your body will be ready to fight the virus if you are exposed. This is important because:

  • it decreases the burden on the stretched health care system.
  • it enables us time to find better treatments.
  • it helps to protect you so you can protect others.

Other steps, like wearing masks and social distancing, help reduce your chance of being exposed to the virus or spreading it to others.

Put together, these efforts will offer the best protection from COVID-19 and bring the pandemic to an end.

Two vaccines have received Emergency Use Authorization from the US Food and Drug Administration (FDA).

Both Pfizer and Moderna vaccines are currently authorized and being distributed throughout the country. 

There are phases of the vaccine distribution to help make sure the vaccines that are available are being given to the higher risk people first. 

  • The first groups of people to receive the vaccination include health care workers, first responders, and people in nursing homes.
  • Then the vaccine will be given to essential workers like those who work in food services, manufacturing, law enforcement, education, transportation, corrections, and emergency response, as well as people over the age of 75.
  • Adults with underlying medical conditions and people over 65 are the third group to get the vaccine.

To get a full view of the timeline for when vaccines will be released, visit Maryland's COVID page here.

Yes, eventually. We don't have a timeline on when Chase Brexton will have vaccines for our patients. Once we do, we will get the information to you.

With both Pfizer and Moderna vaccines, you will need two doses. 

  • Pfizer's second injection must be 21 days after the first.
  • Moderna's second injection must be 28 days after the first.

Two doses help your body to learn how to defend itself against the virus so you can build up immunity to it. 

Yes. Your body will not build up immunity against the virus with just one shot. It will temporarily build up immunity, but the second dose will bring that immunity up to about 95%.

The first dose starts teaching your body how to defend itself. The second dose, when you get it as prescribed, will finish teaching your body how to defend itself.


Herd immunity can be created by:

  • Enough people surviving an illness to create immunity to it, or
  • Vaccination which doesn't cause illness but create immunity to it.

Vaccine-created herd immunity has helped us control many deadly and contagious diseases like smallpox, polio, diphtheria, rubella, and many others.

Natural herd immunity against COVID-19 would mean about 70% of our population would have to get, and recover from, COVID-19. That's at least 200 million Americans who would need to get sick AND fully recover. 

The problem is, at this point, after having COVID-19 you still are able to get it again.


Getting COVID-19 has many drawbacks that getting a vaccine doesn't have.

  • If you get COVID-19 you risk giving it to loved ones who may get very sick.
  • Right now, COVID-19 is the third cause of death in the US. Getting sick with COVID-19 can cause serious illness and death.
  • Immunity after recovering from COVID-19 only lasts for about three months. After that, the antibodies seem to go away.

The vaccines do not cause COVID-19 and likely protect you for about a year.

Yes. Though COVID-19 will give you some antibodies (the immunity you get after being sick), they do not last longer than three months.

You will still be at risk for getting infected with COVID-19 if you do not get the vaccine, continue wearing mask, maintain 6 feet of distance from others, and wash your hands well. 

There are two big reasons for this. 

First, you will not become completely immune to COVID-19; though both vaccines provide around 95% protection, there is still a minor risk of infection.

Second, both the virus and vaccines are new to us. While the vaccines create immunity safely, we do not yet know if they will prevent you from carrying the virus and giving it to others.

About mRNA & Vaccines

mRNA is a natural part of most organisms and has an important job in our body. It is a messenger for DNA. It tells our cells what to make in order to fix, build, or maintain things in our bodies.

For example, mRNA may tell your cells how to heal a wound or it may tell your cells what to make to grow your hair. 

Most vaccines are made with real virus. 

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To make a vaccine using a virus is a long, tough process. Normally scientists have to: 

  • Separate the virus from genetic material
  • Clean it and try to duplicate enough of it to use for research
  • Determine the safest way to use it in a vaccine so it won't cause illness, and
  • Once the vaccine is tested, proven safe and effective, figure out how to grow the vaccine so they can make enough to give everyone who needs it.

mRNA is a nice alternative because it is something natural and safe for our bodies. But, REAL mRNA is not something we can use for vaccines.

Luckily, more than 30 years ago, scientists discovered how to make SYNTHETIC mRNA. Synthetic means fake. 

Synthetic mRNA is made in a lab. It is built with the instructions to tell our bodies how to stop a virus or treat an illness. Then it is put in a liquid made from ingredients already found in humans - salt, sugars, and oils.  Because it is made in a lab and not biological, it is quick, fairly inexpensive, and easy to reproduce so enough is available for everyone who needs it.

Both Pfizer and Moderna vaccines have very similar ingredients in their vaccines:

  • Synthetic mRNA
  • Lipids (oils)
  • Salts (including sodium and saline)
  • Sucrose (sugar)

All of the ingredients will not stay in your body. Once the synthetic mRNA is delivered, they leave your body naturally.

Both vaccines contain polyethylene glycol-2000 (PEG-2000 for short). PEG-2000 is a lipid (or oil) that helps to protect the synthetic mRNA so it can get to our cells and do its job.

There are many types of PEGs and they are commonly used a variety of products. PEG-2000 is an ingredient used in products, like toothpaste, shampoo, make-up, and other medications.

Some people may have hypersensitivity to this ingredient. If you do, talk with your provider about whether the vaccines are right for you.

There a many ongoing studies for mRNA vaccines and disease treatments, including for cancers, genetic disorders, and infectious diseases. 

Several mRNA vaccines are in use in veterinary medicine.

mRNA is a messenger. Once the vaccine is injected, the mRNA travels to our cells. It gives our cells instructions to build a mimic of the virus' spike protein.

Our immune system sees the spike protein as an invader and fights it.

By fighting and destroying these fake spike proteins, our immune system learns what to do if the REAL virus ever enters our body. Instead of getting sick, our immune system is prepared to defend us against the virus.

Learn more here.

About FDA Authorization & Safety Oversight

The Emergency Use Authorization (EUA) authority allows the FDA to help strengthen the nation’s public health protections against public health crises and other threats by making new medical counter measures available for use during public health emergencies.

An EUA is not an FDA approval, but unlike herbal supplements and vitamins, the medication has been verified through major and extensive clinical studies. These medications are also scrutinized by public and private health practitioners and researchers independent of the pharmaceutical company.

The vaccines were studied with nearly 74,000 people as a part of the clinical trials for safety and effectiveness.

These participants were from all walks of life, races, ethnicities, ages, health conditions, and birth sexes.

Studies found no serious safety concerns for those who received it and the studies continue to be ongoing for at least the next year or so. 

Additionally, the FDA has monitored the vaccine development process from the beginning for these vaccines, and continues to monitor for safety:

  • Through random spot checks in which they do a surprise visit and take a bottle of vaccine and test it.
  • Through the Centers for Disease Control and Prevention's (CDC) and FDA's Vaccine Adverse Event Reporting System (VAERS). Anyone who experiences an unexpected side effect should report these using VAERS so the FDA and CDC can investigate and fix the problem.
  • Through the CDC's v-safe health app. After getting your first vaccine dose, you will be able to download the app to provide feedback to the CDC about the vaccine and how you are feeling. This information will help to make sure the vaccines are safe, any issues are addressed, and can help you to know more about your vaccination.

Anaphylaxis is a type of allergic reaction. It has occurred for a small number of people, most with the Pfizer vaccine. For ALL COVID-19 vaccinations, you will be asked to remain for 15 to 30 minutes after the injection to monitor you. The medical personnel will have epinephrine and other life-saving items nearby to be able to care for you should an allergic reaction occur. 

Anaphylaxis has occurred at a rate of 11 out of 1 million vaccinations. 

Vaccine Side Effects & Other Concerns

Every medication - from a vaccine to aspirin to a multivitamin - can have side effects. The side effects are important to know. 


Most common side effects - which could last a couple days and were more noticeable after the second dose of the vaccine - include:

  • pain at the injection site,
  • tiredness,
  • headache,
  • muscle pain,
  • chills,
  • joint pain, and
  • fever.


Most common side effects - which could last a couple days and were more noticeable after the second dose of the vaccine - include:

  • pain at the injection site,
  • tiredness,
  • headache,
  • muscle pain,
  • chills,
  • joint pain,
  • swollen lymph nodes in the same arm as the injection,
  • nausea and vomiting, and

Side effects are actually pretty important signs that your immune system is learning how to fight a virus. This means its working harder and may cause some aches and pains as your immune system learns.

Neither vaccine from Pfizer or Moderna contain ANY virus - there is no chance of getting COVID-19 from the vaccine.

There have been relatively few cases of anaphylactic shock and the majority of those have been after the Pfizer-Biotechnic vaccine. The FDA and Centers for Disease Control and Prevention (CDC) are researching what the cause of these cases has been.

However, as precaution anyone getting the vaccine is monitored for 15-30 minutes after vaccination. 71% of anaphylaxis cases from the vaccination have occurred within 15 minutes of getting vaccinated. 

All vaccine administration sites are screening individuals for past allergic reactions to vaccinations and are stocked with epi-pens and other treatments to ensure swift response. The risk of anaphylactic shock is much lower than the risk of getting or dying from COVID-19.

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The rumor that the vaccine impacts fertility is driven by social media and without any clinical evidence. There are no scientific concerns even suggest issues of fertility. The same holds true to the DNA rumor, which has been driven by social media and not scientific fact.

The mRNA in the vaccines is designed to teach our bodies how to fight the Sars-COV-2, the virus that causes COVID-19. It cannot do anything else. Once the mRNA is delivered, it disappears. The rest of the ingredients—lipids, salts, and sugars—have been frequently used in many things and are closer to our own body's natural ingredients. None of the ingredients in these vaccines have any impact on fertility or our DNA.

You may experience side effects for a few days after the vaccine. If you are concerned, call your provider.

The Vaccines & Health Conditions

The vaccines haven't been approved for pregnant or nursing individuals.

Studies for new vaccines and medications start with healthy individuals over 18 who aren't pregnant or nursing. Later in the studies, individuals with health conditions are added. Babies, children, and pregnant people are generally the last to be studied, after safety has been proven for everyone else. 

Both the Pfizer and Moderna vaccines are currently being studied to see if they are safe during pregnancy and for those nursing.

Not yet. Children as young as 12 have been added to the vaccine studies. However, there is a bit more research to do before either vaccine is available for babies and children.

Right now, the Pfizer vaccine is authorized for use those aged 16 and up and the Moderna vaccine is authorized for use in those aged 18 and up.

Yes, absolutely. Both the Pfizer and Moderna trials included HIV-positive individuals, and no specific side effects related to their HIV status were reported. Remember, the vaccines do not include any virus material, living or dead, so there is no chance that someone can contract COVID-19 from taking the vaccine.

In fact, there’s good reason for those living with HIV to take the vaccines. Data is showing that people living with HIV who contract COVID-19 often have worse outcomes and are at higher risk of serious complications. Getting the vaccine is important for everyone, but may be particularly important for those living with HIV.

Yes! Both vaccine studies had people with a variety of health conditions - many serious - and these vaccines were safe for them. Learn more about the study participants here.

If you have a chronic health condition, you are more at risk for developing complications if you get COVID-19. When you are able, you should get the vaccine.

There are three answers to this question.

First: If you have had an allergic reaction to other types of vaccines

If you have had an immediate allergic reaction—even if it was not severe—to a vaccine or injectable therapy for another disease, ask your provider if you should get a COVID-19 vaccine. Your primary care provider will help you decide if it is safe for you to get vaccinated.

Second: If you have allergies not related to vaccines

CDC recommends that people with a history of severe allergic reactions not related to vaccines or injectable medications - such as food, pet, venom, environmental, or latex allergies - get vaccinated. People with a history of allergies to oral medications - like sulfa drugs, NSAIDs - or a family history of severe allergic reactions may also get vaccinated.

Third: If you have had an allergic reaction to polyethylene glycol (PEG) or polysorbate

Polysorbate is not an ingredient in either mRNA COVID-19 vaccine but is closely related to PEG, which is in the vaccines. People who are allergic to PEG or polysorbate should not get an mRNA COVID-19 vaccine.

Learn more at the CDC.

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