COVID-19 Vaccine Frequently Asked Questions (FAQ)

Scheduling and Administration


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What do we know so far about this new variant of the novel coronavirus?

Genomic data in the UK identified a new variant called B.1.1.7 or VUI-202012/01. It has acquired 17 mutations located on the gene that encodes for the Spike protein on the surface of SARS-CoV-2, which is how the virus binds and enters cells. We don’t yet know the full effect of these mutations, but over the past several weeks there has been a rapid increase in the number of COVID-19 cases in parts of England. Although more information is being learned regarding its full effect, it appears this new variant is more transmissible and there is concern that it will become the dominant global variant over time.

Are coronaviruses known to change like this, and if so, could there be other undetected variants out there?

Yes, the coronavirus is an RNA virus, and this type of virus is known to develop mutations over time. There could be other variants out there, but there are programs in place that look at the genetic sequence of a percentage of positive coronavirus samples to detect things like this. We have also seen other variants throughout this epidemic.

Is there any evidence that the COVID-19 vaccines that have already been developed and authorized will be less effective against the new variant?

Not at this time. The vaccines should continue to be effective against coronavirus. It is possible that over time and with the development of many other mutations in the coronavirus that the vaccine could be less effective. One of the benefits of the mRNA vaccine is that it would be easy for scientists to alter the vaccine if this were to happen.

Will the variant alter our current approach to reduce transmission?

Since we know that the new variant can be more easily transmitted, it is important that we reinforce and adhere to our public health approaches to reduce transmission of COVID-19. Every person should wear face masks, use good hand hygiene, maintain at least 6 feet of physical distance from others, and avoid crowds. The way we prevent other mutations from developing is by decreasing the overall levels of coronavirus circulating in the community.

What should providers tell their patients about the variant?

While the development of this variant is concerning and there is much we need to learn, we do know it is more easily transmissible. This can increase the number of cases in the population, which is why it is important for individuals to double down on public health measures and to get vaccinated when it is their chance. We are all in this together, and everyone has a role to play in helping to get this pandemic under control.

MUSC Health is utilizing every FDA-approved vaccine, which currently includes those by Pfizer/BioNTech, Moderna, and Janssen (Johnson & Johnson).

Vaccine Basics

  • The Pfizer/BioNTech vaccine is two shots separated by 21 days.
  • The Moderna vaccine is two shots separated by 28 days.

Note: The CDC has stated that if it is not feasible to adhere to the recommended 19-23 day interval, the second dose of Pfizer-BioNTech and Moderna vaccines may be scheduled for administration up to 6 weeks (42 days) after the first dose.

If it has been greater than the recommended time frame to get the second shot, the CDC advises to get it at the earliest opportunity. It is important to note that you do not need to restart the vaccination series. Note: The CDC has stated that if it is not feasible to adhere to the recommended 19-23 day interval, the second dose of Pfizer-BioNTech and Moderna vaccines may be scheduled for administration up to 6 weeks (42 days) after the first dose.

Yes, you need to get both shots of the vaccine. Efficacy of a single dose has not been evaluated.

Vaccine record cardYou will receive a COVID-19 Vaccination Record Card that looks like this:

Vaccines decrease the risk of a person getting a disease by working with the body’s natural defenses (immune system) to build protection. A vaccine is a safe way for your body to develop an immune response to a dangerous germ without making you sick and is a preventative measure that helps protect us from getting sick.

When you get vaccinated, the following occurs:

  • Your body recognizes the invading germ (virus or bacteria).
  • Proteins (antibodies) are produced which are naturally made by the immune system to fight disease.
  • The antibodies are trained to remember the disease and how to fight it, so if you are exposed to the germ again your immune system can quickly destroy it before you become sick.

The Pfizer/BioNTech and Moderna vaccines are both mRNA vaccines and give instructions to our cells to make a harmless piece of the coronavirus spike protein. The spike protein is found on the surface of the coronavirus and is responsible for entry into human cells. The vaccine is administered to humans in the upper arm; once given, the mRNA enters the cell and our body’s normal protein-making machinery “translates” those instructions to make the spike protein. After this occurs the cell breaks down the mRNA and displays the protein piece on its surface. Since the protein is not supposed to be there, the immune system recognizes it as “foreign” and mounts an immune response by developing antibodies that are specific to this spike protein.

Since you have developed antibodies to the spike protein if you are exposed to the coronavirus in the future your body is able to mount an antibody response which protects you from getting sick.

There are various types of vaccines being developed against SARS-CoV-2, the virus which causes COVID-19.

  1. Inactivated or Attenuated: One of the most traditional methods for developing vaccines is to use inactivated (killed) virus so it can no longer multiply. When injected into the cells, the virus cannot multiply and the individual develops antibodies to the inactivated part of the virus. Other vaccines that work in this manner are influenza vaccine, inactivated polio vaccine, and hepatitis A vaccine.
  2. Viral Vector Vaccines: These are a newer type of vaccine where the SARS-CoV-2 gene for the spike protein (the protein found on the surface of the coronavirus and responsible for entry into the human cells) is inserted into a harmless virus (i.e., Adenovirus). It delivers the gene to human cells, where the spike protein is produced and then stimulates the immune response to produce antibodies. The most common viral vector is Adenovirus and there are several vector vaccines in advanced clinical trials (i.e., AstraZeneca).
  3. Genetic Vaccines: These deliver one or more of the coronavirus’s own genes into cells to stimulate an immune response. The Pfizer/BioNTech and Moderna vaccines are examples of genetic vaccines made from a molecule called messenger RNA (mRNA). The spike protein is found on the surface of the coronavirus and responsible for entry into the human cells. An mRNA vaccine contains genetic instructions that teaches our cells how to build a harmless piece of the coronavirus spike protein. When injected into cells, the vaccine causes cells to make these spike proteins and display a piece on its surface. Once the spike protein is made, the cell breaks down the instructions and gets rid of them.
    Simultaneously, our immune system recognizes the protein doesn’t belong there and triggers an immune response in our body to make antibodies which are stimulated to protect us from getting infected when our body is exposed to the real virus.
    Although there are currently no licensed mRNA vaccines in the United States, scientists having been studying and working with them for years. Interest in these types of vaccines has increased since they can be scaled up quickly and have been studied for various pathogens (Influenza, Zika, Rabies, Cytomegalovirus).
  4. Protein Based Vaccines: Vaccines that contain coronavirus proteins but no genetic material. Some contain whole proteins while some have fragments of them. They pack many of these molecules on nanoparticles.

It is an mRNA vaccine and is administered as 2 doses given 21 days apart. The Phase 3 clinical trial enrolled individuals who were > 12 years of age and non-pregnant/non-breastfeeding women. There were 43,661 participants with 41,135 individuals who received 2 doses of the vaccine.

Vaccine efficacy was based on 170 cases of COVID-19 that occurred 7 days after the second dose. Of the 170 cases, 162 cases of COVID-19 occurred in the placebo group, and 8 cases in the vaccine group. Since participants were randomly assigned to get vaccine or placebo, and were equally likely to get either, it is assumed that individuals in each group had the same likelihood of being exposed to the coronavirus during the study period. Since so many fewer people who got vaccine ended up being infected compared with those who got placebo (more than 20 times fewer), the overall efficacy is measured at 95%.

There were 10 cases of severe COVID-19, with 1 in the vaccine group and 9 in the placebo group.

The study had good representation globally with participants from 150 clinical trials sites including the United States, Germany, Turkey, South Africa, Brazil, and Argentina. Overall 42% of global participants and 30% of U.S. participants were from racially and ethnically diverse backgrounds.

On December 2, 2020 the United Kingdom gave emergency authorization to the Pfizer/BioNTech vaccine. The FDA reviewed the vaccine for Emergency Use Authorization on December 11, 2020.

Pfizer-BioNTech COVID-19 Vaccine EUA Fact Sheet for Recipients (PDF)

It is an mRNA vaccine and is administered to individuals as 2 doses given 28 days apart. The Phase 3 clinical trial was completed in collaboration with NIAID and enrolled over 30,000 participants who were > 18 years of age and non-pregnant/non-breastfeeding women.

The primary endpoint was based on analysis of COVID-19 cases starting two weeks following the second dose of the vaccine. There were 95 cases of COVID-19; 90 cases in the placebo group and 5 cases in the vaccine group, for an overall vaccine efficacy of 94.5%.

Of the 95 cases of COVID-19, 15 occurred in adults >65 years old and 20 were in those from diverse communities.

There were 30 cases of severe COVID-19. All were in the placebo group.

Moderna has started a trial to test the vaccine in children between 12-18 years old.

The duration of protection from the vaccine is not yet known and continues to be studied. This is one of the reasons it is important to continue to wear your masks, practice physical distancing, use good hand hygiene, and avoid large crowds even after you get the COVID-19 vaccine.

Protection from the vaccine is not immediate and the vaccine is a 2-dose series. It will take 1 to 2 weeks following the second dose to be considered fully vaccinated.

Yes, you should receive the same vaccine product for your 2nd dose as you received for your 1st dose.

According to the CDC, in exceptional situations, in which the vaccine product given for the 1st dose cannot be determined or is no longer available, any mRNA vaccine (currently Moderna and Pfizer/BioNTech) may be administered at a minimum of 28 days between doses. It is preferable to delay the 2nd dose (up to six weeks) to receive the same product than to receive a mixed series using different products.

Side Effects & Safety

For both the Pfizer/BioNTech and Moderna vaccine the side effects were mild to moderate.

After the first injection the most common side effect was an injection site reaction.

Side effects were most common after the second dose and included fatigue, muscle aches, headaches, pain, fever, and redness/pain at the injection site.

View more information on side-effects of the Pfizer/BioNTech COVID-19 vaccine (PDF).

There is not enough information known about long-term natural immunity in people who have been infected with COVID-19. The protection a person develops after having an infection varies depending on the disease and most likely varies from each individual. Since this is still a new disease, we do not know how long natural immunity lasts. The Pfizer phase 2/3 trial included participants who had evidence of prior infection and it suggests that the vaccine is safe and efficacious in those who have had prior infection.

The CDC’s Advisory Committee for Immunization Practices (ACIP) recommends that the COVID-19 vaccine should be offered to those with a history of COVID-19. However since current evidence suggests that reinfection is uncommon in the 90 days after initial infection, those with a documented acute infection in the preceding 90 days may defer vaccination until this point.

Vaccination with the COVID-19 vaccine should be deferred until recovery from acute illness has occurred and criteria has been met to discontinue isolation. The ACIP does not recommend there be any minimal interval between infection or vaccination but does note that current evidence suggests that reinfection is uncommon in the 90 days after initial infection. Therefore, those with a documented acute infection in the preceding 90 days may defer vaccination until this point especially while there is a limited supply of vaccine.

There is currently no data on the safety or efficacy of the COVID-19 vaccine in persons who have received monoclonal antibodies or convalescent plasma for coronavirus therapy. Based on the ACIP recommendations, vaccination should be deferred for at least 90 days after treatment with a monoclonal antibody or convalescent plasma to avoid interference of the treatment or vaccine- induced immune responses. This is based on the estimated half-life of therapies and evidence suggesting that reinfection is uncommon in the 90 days after initial infection.

None of the vaccines uses the live coronavirus which causes COVID-19, so the vaccine cannot cause the disease. The goal of the vaccine is to teach our immune system how to recognize and “fight” the virus which causes COVID-19. Sometimes the process of getting vaccinated can cause mild fevers, muscle aches, soreness, and headaches as your body’s immune system starts producing the protective antibodies to help defend you in case you are exposed to the virus.

It takes a few weeks for the body to build immunity after it receives a vaccination. Thus a person could get sick with COVID-19 before or after they receive the vaccination and this means they have not had enough time to develop an appropriate antibody response.

There were two individuals with a history of significant allergic reactions in the United Kingdom who developed anaphylactoid reactions from the Pfizer vaccine. This type of reaction would likely occur immediately or very soon after receiving the vaccine.

The CDC’s ACIP is recommending that individuals with a history of severe allergic reaction (anaphylaxis) to any component of the Pfizer BioNTech vaccine should not be vaccinated at this time until more information is known.

Those with a history of severe allergic reaction (anaphylaxis) to another vaccine or history of severe allergic reaction (anaphylaxis) to an injectable medication do a risk assessment and may consider deferral of the vaccine at this time. If these individuals proceed with vaccination, they should be monitored for 30 minutes post-vaccination.

Those with a history of food, pet, insect, venom, environmental, latex allergies, history of allergy to oral medications (including oral equivalent of injectable medications), non-serious allergy to vaccine or other injectable (no anaphylaxis), or family history of anaphylaxis should proceed with vaccination. These individuals should be monitored for 15 minutes.

Please continue to monitor this information as it will be updated as needed. If you have questions regarding if you are a candidate for the Pfizer COVID-19 vaccine at this time please discuss it with your physician prior to proceeding.

Visual representation of the vaccination decisions outlined in the text above

If you get diagnosed between your first and second doses of the vaccine, finish your quarantine period before coming to your 2nd vaccine appointment. You can receive your 2nd vaccine dose after your quarantine period ends.

We currently have approximately 6 months of followup data on individuals who have received the vaccine and up to 9 months in individuals who were enrolled in the phase 1/2 clinical trials that enrolled many fewer patients.


Receiving the COVID-19 vaccine will not cause you to test positive for a test checking to see if you have a current infection for COVID-19. Once your body develops an immune response, which is the goal of vaccination, you may test positive on some antibody tests for COVID-19.

Antibody tests tell us you have protection against the virus. Scientists are currently working to understand how COVID-19 vaccination may affect antibody tests.

Persons with HIV infection, other immunocompromising conditions, and those who take immunosuppressive medications may be at increased risk for COVID-19. There is no data currently available to establish the safety and efficacy of the vaccine in these groups.

Based on what is known, the ACIP recommends that these individuals may still receive the COVID-19 vaccine unless otherwise contraindicated. They should be counseled about the unknown vaccine safety and efficacy profiles in immunocompromised persons, the potential for reduced immune responses, and the need to continue to follow current guidance to protect themselves against COVID-19 (good hand and respiratory hygiene, wearing facemasks, maintaining physical distance, and avoiding crowds).

Per the ACIP, the Pfizer or Moderna vaccines should not be administered within 14 days of another vaccine (influenza, for example). The CDC also discourages “mixing” COVID-19 vaccines, meaning if you get a Pfizer first dose, the CDC recommends also getting a Pfizer second dose. However, if it is not possible to get the same brand for your second dose, it is better to “mix” vaccine brands (e.g. first dose Pfizer and second dose Moderna) than to not get a second dose at all.

There is currently not enough evidence on the safety and efficacy of COVID-19 vaccines in patients with autoimmune disorders. The CDC recommends discussing with your physician whether you should take the vaccine.

The effectiveness of COVID-19 vaccines is still being studied in solid organ transplant recipients. In general, solid organ transplant recipients have lower antibody responses and waning antibody titers compared to those without transplants. Additionally, those vaccinated pre-transplant may have decreased protection post-transplant especially if they receive therapies which affect B-cell function.

Currently the immunogenicity and efficacy of the COVID-19 vaccines are unknown in transplant recipients.

Based on prior vaccination guidelines for SOT recipients 2020 12 08 COVID 19 VACCINE FAQS that all transplant candidates and their household members receive the vaccine when it becomes available to them.

General Questions

Updated advice on the most current recommendations for vaccinated people may be found on the CDC's website.

  • We would recommend contacting the clinical trial coordinator of the vaccine study you are currently enrolled in if you are considering dropping out.
  • Antibody testing is NOT satisfactory to determine if you got active vaccine or placebo. Please follow the instructions below to request unblinding.
  • If you have a scheduled appointment for the authorized Pfizer or Moderna vaccine, you can request to be unblinded to find out if you received the active vaccine or placebo. However, this may affect your continued participation in the study and you should speak to the clinical trial coordinator. If you would like to be unblinded please complete the AstraZeneca Unblinding Request Form, be prepared to upload documentation of your scheduled authorized vaccine appointment. There is no information available as to the risks or benefits of getting the authorized vaccines if you have already received the study vaccine.

This information is likely to change frequently.