A syringe is filled with the Pfizer COVID-19 vaccine for the first immunizations offered to UCI Health frontline caregivers on Wednesday, Dec. 16, 2020.

COVID-19 Vaccine FAQ

We all want this pandemic to end. By early February 2021, the coronavirus has caused 100 million confirmed infections and 2.2 million deaths worldwide. More than 500,000 Americans have died due to COVID-19-related illnesses, which now exceeds heart disease as the leading cause of U.S. deaths. 

During the current winter surge, the virus claimed about 3,300 U.S. lives every day. But safe and effective vaccines can end the pandemic if, as experts believe, at least 70% of people are vaccinated.

Two COVID-19 vaccines have received emergency approval for frontline healthcare workers and residents of long-term care homes. UCI Health infectious disease experts answer questions about these vaccines. (View the FAQ in Spanish ›)

Q. Why should I get the COVID-19 vaccine?
A. In addition to preventing infection and death by reducing your chances of getting sick, the COVID-19 vaccines also will prevent many long-lasting effects reported by COVID-19 patients. 

These include fatigue, shortness of breath, cough, muscle and joint pain, chest pain, difficulty thinking and concentrating (“brain fog”), depression, headache, and fever that comes and goes. Some people also reported heart, lung, kidney, skin, teeth and nervous system problems.

Q. Should I get the COVID-19 vaccine now or wait?
A. With 100 million cases of COVID-19 worldwide and 26 million cases in the U.S., we should not wait to receive the vaccine. Over 30 million doses of mRNA vaccine have already been given in the U.S. alone, and the safety data are excellent. For example, serious allergic reactions are rare (11 per 1 million people vaccinated). With safe and highly protective vaccines, there is no reason why another person (including ourselves, our family, or our friends) needs to die from COVID-19. We should be urgently vaccinating. Being vaccinated enables us to protect our workplace and our close circle of friends and family. The sooner we can reach 70-85% vaccinated, the sooner the pandemic can come to an end. 

Q. What COVID-19 vaccines are now available?
A. Several companies are developing vaccines that work against SARS-CoV-2, the virus that causes COVID-19. Two have been tested in large-scale clinical trials and have received emergency authorization by the FDA (Food and Drug Administration). They are:

  • Pfizer-BioNTech mRNA vaccine
    • Granted Emergency Use Authorization (EUA) on 12/11/2020
    • Large-scale trial (44,000 participants) showed 95% efficacy
    • Two-dose vaccine, requires ultra-cold storage (–70 Celsius)
    • First shipments to hospitals that can handle ultra-cold storage
    • 50 million doses to the world by end of 2020 (6.5 million to U.S.)
    • 1.3 billion doses to the world in 2021
  • Moderna mRNA vaccine
    • Emergency Use Authorization (EUA) status granted 12/18/2020
    • Large-scale trial (30,000 participants) showed 94% efficacy
    • Two-dose vaccine, requires standard cold storage (–20 Celsius)
    • First shipments to hospitals and pharmacies serving long-term care facilities
    • 20 million doses to the world by end of 2020
    • 500 million to 1 billion doses to the world in 2021

Q. What is in the vaccine? What is an mRNA vaccine?
A. The two vaccines authorized for use in the U.S. are both mRNA vaccines. mRNA stands for “messenger ribonucleic acid,” and it is an instruction set to make proteins. Every cell in our bodies has mRNA in it because we need proteins to survive. The mRNA in the Pfizer and Moderna COVID-19 vaccines provide instructions for your body to make a specific protein (Spike protein) on the surface of the SARS-CoV-2 virus. When your body makes this viral protein, it is recognized as not human, and your body develops antibodies to it. These antibodies protect you if you later encounter the virus. Some vaccines inject the protein itself, but mRNA vaccines inject the instructions needed for your body to make the protein. 

After making the protein, your body will destroy the mRNA. The mRNA does not stay in your body. It is temporary and does not mix into your genetic code. The COVID-19 vaccines are not the first mRNA vaccines. mRNA vaccines have been made for flu, rabies, CMV (cytomegalovirus), and Zika viruses.

Q. Can the COVID-19 vaccines give me COVID?
A. None of the currently developed COVID-19 vaccines have the live SARS-CoV-2 virus. These vaccines cannot give you or anyone else COVID-19, nor do they make you contagious.

Q. Should I worry that the vaccine was made so quickly? Were steps skipped?
A. No steps were skipped. All COVID-19 vaccines being submitted for approval must meet high U.S. safety standards. All vaccines to be distributed in the U.S. were helped by funds from the government (e.g., Operation Warp Speed), large companies or both. These funds helped speed three processes:

  • Trial enrollment — If you increase the number of staff members who are recruiting patients, you can enroll a lot of people into a clinical trial in a shorter time period. The funds helped the trials quickly enroll tens of thousands of participants.
  • Manufacturing — Funds help increase the number of available manufacturing plants, warehouses and employees. The molecular-based mRNA vaccines also can be manufactured faster because they do not require growing the virus to produce virus proteins.
  • Distribution — Funding enables the vaccines to be shipped rapidly around the nation and the world on a regular basis.

Q. What is the difference between Emergency Use Authorization (EUA) status and full FDA (Food and Drug Administration) approval for a vaccine?
A. When an effective vaccine has been demonstrated in a trial, it can apply for EUA status with two months of post-vaccine safety data. To apply for full approval, six months of post-vaccine safety data must be provided.

The FDA is encouraging companies who receive EUA status to apply for full approval as soon as possible. Both mRNA vaccines have reported outstanding safety data with no serious side effects.

Q. Who pays for the vaccine?
A. At this time, the two mRNA vaccines are free because the U.S. government has purchased millions of doses. In the future, this may change: The government may purchase more doses, your insurance may cover the cost or you may be able to pay out of pocket.

Q. How well does the vaccine work? Should I get Pfizer or Moderna?
A. The Pfizer and Moderna COVID-19 vaccines have both been tested in large vaccine trials involving tens of thousands of participants. Participants were randomized to receive the vaccine or a placebo injection. Then, they were allowed to live their lives and mix with their communities as they normally would. Since the trial is randomized, large numbers should ensure that the type of human interactions in one group are similar in the other. The trials reported a remarkable 94-95% efficacy in preventing COVID-19 cases. 95% efficacy means that the vaccine group had only 5% of the cases seen in the placebo (non-vaccine) group. For example, if the placebo (non-vaccine) group had 100 cases of COVID-19, the vaccine group would only have 5. Importantly, the vaccine not only prevented COVID cases overall, but it prevented severe COVID-19 disease.

Protection was measured after the second dose for both vaccines. Pfizer studied the amount of protection 7 days after the second dose, and Moderna studied the amount of protection 14 days after the second dose.

  • Pfizer COVID-19 vaccine Phase 3 trial (~44,000 participants)
    • 95% efficacy (protection)
    • All COVID-19 cases: 162 in placebo group vs. 8 in vaccine group
    • Severe COVID-19 cases: 9 in placebo group vs. 1 in vaccine group
  • Moderna COVID-19 vaccine Phase 3 trial (~30,000 participants)
    • 94% efficacy (protection)
    • All COVID-19 cases: 185 in placebo group vs. 11 in vaccine group
    • Severe COVID-19 cases: 30 in placebo group vs. 0 in vaccine group

Q. Which vaccine is better?
A. These trials show that these vaccines are twin vaccines. They are both mRNA vaccines, they were made by two different companies which tested them in two large clinical trials, and both were found to be ~95% protective. This is the best result that scientists could hope to see. Nearly identical results from two completely different large trials.

Both vaccines performed well across the age spectrum. Note that they used different age groupings when providing summary data to the FDA. It is likely that if they used the same age groupings, that the results would be very similar.

  • Pfizer
    • 16-55 years old: 96% efficacy
    • >55 years old: 94% efficacy
  • Moderna
    • 18-<65 years old: 96% efficacy
    • 65+: 86% efficacy

The results of these vaccine trials were submitted in full to the FDA, shared with the CDC’s Advisory Committee on Immunization Practices (ACIP), and published in the New England Journal of Medicine (https://www.nejm.org/doi/full/10.1056/NEJMoa2034577; https://www.nejm.org/doi/full/10.1056/NEJMoa2035389).

Q. Am I protected as soon as I receive the vaccine? Can I stop wearing a mask?
A. No. The protection was measured starting 7 days after the second dose for the COVID-19 Pfizer vaccine and 14 days after the second dose for the COVID-19 Moderna vaccine. Until that time, you should assume you have no proven benefit from the vaccine. In addition, even after you are vaccinated, all policies, protocols, and public health orders related to COVID-19 will remain in place until you are notified otherwise. This is a contagious disease and we are all in this together. In addition, there are still cases of COVID-19 in the community. With 95% protection, you can still get COVID, especially if there are lot of people around you who may have COVID. Experts believe that 70-85% of the population will need to be vaccinated before the pandemic will be over. 

Q. After vaccination, can I still spread COVID-19 to my friends and family?
A. Although the vaccine is 95% protective, there is a 5% risk of breakthrough disease despite being vaccinated. This 5% risk can be important when there are a lot of people in the community with COVID-19. If you develop symptoms of COVID-19, you should be tested, and if you test positive, you are likely contagious to others. Fortunately, there is evidence from other vaccines (for example, measles) that vaccination may make you less contagious to others if you are infected.

Q. Will vaccination make me more likely to have asymptomatic disease and pass COVID-19 to others without knowing it?
A. There are several reasons why this is unlikely to happen. First, both Pfizer and Moderna trials are evaluating the likelihood of asymptomatic disease and more data will be known over time. Moderna already reported that asymptomatic disease was greatly reduced at the time of the second vaccine dose. At UCI Health, our healthcare providers are routinely offered asymptomatic testing for COVID-19, and we have similarly found a marked reduction in both symptomatic and asymptomatic disease after vaccination. Second, there is no carrier state for COVID-19. The virus does not sit in the throat or nose waiting to infect someone. Third, there is no precedent for a highly effective vaccine against a virus that prevents symptomatic, but not asymptomatic, disease. This has not been shown to occur. 

Q. How long will the vaccine protect me?
A. Participants in the Pfizer and Moderna trials will be followed for two years, including having blood drawn periodically to determine if protective levels of antibody are still present. Thus, more will be known as time goes by. Since immunity to other coronaviruses is known to last one to three years, it is widely anticipated that the COVID-19 vaccine will be an annual vaccine, possibly every other year at best. An annual vaccine may also help address variants, since the vaccines can be modified each year, similar to what is currently done for the flu vaccine. Although the first series of the vaccine is a two-dose series, it is likely that an annual vaccine would be a single dose.

Q. What is important to know about COVID-19 variants?
A. When the SARS-CoV-2 virus causes infection, it enters the body and starts to grow. Each time the virus doubles, it can form mutations in its genetic code. This causes slightly different variants of the virus, and over time, many different variants now exist in the world. Finding these variants is made possible because we can sequence the virus’ genetic code. There are several concerns related to variants, including whether some will be better at infecting people, spreading between people, or causing severe disease and death. One of the most important concerns about variants is whether the current vaccines will work on all of them.

Q. What kind of information is most helpful about deciding if a variant will cause a vaccine to fail? 
A. Lots of media attention has been given to whether a variant might evade (or escape) a vaccine. Certain information is more helpful than others to decide whether that is likely to happen. So far, studies using blood from fully vaccinated people have shown that the Pfizer and Moderna vaccines are protective against the UK and South African variants.

Usefulness of Information on whether a Variant can Cause a Vaccine to Fail 

  • Can cause outbreaks
    •  Low
  • Has mutations in spike protein
    • Low unless mutations proven to cause vaccine failure
  • Blood from recovered persons (convalescent sera) doesn’t work
    • Low. Infection is known not to protect well
  • Blood from fully vaccinated persons doesn’t work
    • High. Be attentive to these type of data which is the most valuable for showing that a vaccine may fail
  • Variant COVID cases continue to occur in vaccinated people
    • High. If cases due to a variant keep occurring in fully vaccinated people, this would suggest vaccine failure.

Q. What can we do to stop variants?
A. Variants appear as more and more people become infected and the virus keeps growing in many people. The best solution is for as many people as possible to get vaccinated quickly to stop the spread and growth of the virus.

Q. Were different races and ethnicities included in the vaccine trials?
A. The distribution of race and ethnicity for the mRNA vaccine trials is found below.

  • Pfizer
    • Non-White  Race: 10% African American, 4% Asian, 3% Other racial groups
    • Hispanic/Latinx: 26%
  • Moderna
    • Non-White  Race: 10% African American, 5% Asian, <3% Other racial groups
    • Hispanic/Latinx: 20%

All vaccines are meant to get rid of germs and diseases that infect humans. These vaccines are meant to help humans fight off non-human pathogens. Thus, we do not expect a difference by race or ethnicity. In fact, there is no example of a vaccine where different ones are recommended based upon race or ethnicity.

Q. Will getting the COVID-19 vaccine make me test positive for COVID-19 if am tested after being vaccinated?
A. No. The vaccine will not cause you to test positive on viral tests for COVID-19, such as PCR tests or antigen tests. However, the vaccine will cause you to test positive for certain antibody tests (also called serology) that look for antibodies against the spike protein since the vaccine helps build these antibodies to COVID-19.

Q. Who should get the COVID-19 vaccine? Who should not?
A. All eligible adults should receive the vaccine to protect themselves and their loved ones from COVID-19. The only contraindications are if you have had a serious allergic reaction to the vaccine or its ingredients, or if you have a serious bleeding disorder and your doctor has told you that you cannot get shots into the arm. Because the vaccine provides outstanding protection against COVID-19, including protection from hospitalization and death, if you think you cannot get the vaccine, please discuss with your doctor to confirm whether or not you are truly unable to receive these vaccines. There are special circumstances that will affect the timing of when to get the vaccines (see next several questions). At this time, the vaccines are not authorized for children, but this is expected to change in the future.

Q. I already had COVID-19. Am I supposed to get the vaccine? If so, when?
A. Yes. Anyone who has had COVID-19 should still receive the vaccine. Unfortunately, having been infected with COVID-19 does not guarantee strong immunity to the virus. Usually protection only lasts 3 months after infection. Getting the vaccine will ensure you are protected with the 95% protection found in the trials. You should not receive the vaccine while you are actively infected, but after you return to normal activities, you can and should receive the vaccine when you are eligible. This can be as early as 10 days after your COVID-19 symptoms began. If you are eligible and there is a vaccine shortage, you can wait up to 90 days after infection to receive your vaccine. During that period, you should still be protected from repeat COVID-19 infection. However, remember that full protection from vaccination only occurs after both doses are received, which takes several weeks.

Since the vaccine does not work immediately, some people will become infected with COVID-19 between the first and second doses of the vaccine, or even shortly after receiving the second dose. If this happens, there is no reason to worry that the first dose of the vaccine won’t work. In fact, it is likely that the combination of the vaccine and the infection will cause a strong immune response. However, it is still important to receive the second dose to ensure that immunity is locked in and the full 95% protection is achieved. The second dose can be received on time if you are no longer infectious, have not had a fever for at least 24 hours, and feel up to receiving the vaccine.  If not, you should delay the second dose until those criteria are met. Even with a few weeks’ delay, you should still expect to receive full benefit from the two doses.

Some people who have COVID-19 have received monoclonal antibodies or convalescent sera to help prevent severe disease. If so, you should not receive the vaccine for 90 days from the time you received the antibody therapy since those antibodies can bind the spike protein produced by the vaccine and prevent your body from making its own protective antibody. 


Q. Are pregnant, breastfeeding, or immunocompromised persons supposed to get the vaccine?
A. Persons who were pregnant, attempting to become pregnant, breastfeeding, living with an immunocompromising condition, or taking medication that compromises the immune system are often not enrolled into initial vaccine trials. However, even though these persons were not enrolled in the mRNA trials, we know that pregnant or immunocompromised persons are at higher risk for serious COVID-19 disease. For this reason, persons with these conditions may want to make a personal choice to receive the vaccine. 

For those who are pregnant, breastfeeding, or trying to become pregnant, there are several factors to consider in your personal choice. First, consider your personal risk for becoming infected with COVID-19 because of the number of cases in your community, and your usual level of interaction with family, friends, and others in the community. Second, in general, concerns for any potential medication effects to a developing fetus are usually related to the first trimester when organs are forming. Third, the mRNA in the vaccines do not cross the placental barrier and will not reach the fetus. On the contrary, protective antibodies do pass to your baby through the placental barrier and through breastfeeding. Even though no trial data can be used to provide a recommendation for protection or safety, there are at least 36 participants in the mRNA trials who became pregnant during the trials, including 18 in the vaccine group. They are being monitored for any effects. Discuss your desires and concerns with your doctor.

The American College of Obstetricians and Gynecologists has released the following recommendation, suggesting that vaccine be offered to pregnant and breastfeeding women, and recommending against requiring women of childbearing age to have a pregnancy test before receiving the vaccine.


In general, the concern for immunocompromised persons is not due to safety concerns, but rather that the vaccine may not generate as strong a protective response as in persons with a normal immune system. Nevertheless, a partial response may be an important benefit. Discuss your preferences and options with your doctor. For example, the American Society of Transplantation makes the recommendation that all transplant patients and their household members receive the COVID-19 vaccine when it becomes available.


Q. When will children be able to be vaccinated?
A. Currently, the Moderna and Pfizer vaccines are only authorized for adults (18 years and older for Moderna, and 16 years and older for Pfizer). Trials are underway in children 12 years and older, which are expected to complete this summer. If successful, that could lead to authorization for those age groups by this summer or fall. Trials for children under 12 years old are expected to begin this summer, and would take several months to complete. Thus, vaccination is unlikely to be available to school-aged children before school begins this fall. For this reason, it is even more important for parents and other adults to be vaccinated to provide protection for children. It also means that infection prevention strategies will still be important for school-aged children until a safe and effective vaccine becomes available to those age groups. 

Q. Who is prioritized to get the vaccine?
A. As of early February 2021, the following are eligible to receive the vaccine in Orange County.

  • Healthcare personnel (e.g. hospitals, nursing homes)
  • Residents of long-term care facilities
  • Persons 65 years or older

We anticipate that essential workers in education, childcare, food services and agriculture will soon be added. In addition, an age-based progression will also follow with younger and younger adults being added. In addition, vaccines are now being deployed to major pharmacies across the U.S.. It is likely that vaccine will be widely available to any adult who wants it by mid-April. 

Q. How many doses are arriving in 2021? Where can I get vaccinated?
A. The vaccine supply to the U.S. will be greatly increased in the coming months. Pfizer provided 29 million doses to the U.S. in 2020, and will provide 200 million more by May 2021. Moderna will provide 100 million doses by end March 2021, and another 100 million doses by end June.

This will enable vaccines to become increasingly available, including at local pharmacies. Those eligible for the vaccine can obtain it through their medical provider or through public health Super Pods by registering through the Othena app (https://occovid19.ochealthinfo.com/covid-19-vaccine-resources). 

Q. Will the COVID-19 vaccine be required?
A. Currently, a variety of vaccines, such as measles-mumps-rubella, chickenpox, and polio are required in certain settings – for school, college, and in healthcare settings. This past year, the University of California required the flu vaccine on all its campuses. The ability to require the COVID-19 vaccine would be dependent on several factors, including obtaining full FDA approval (instead of Emergency Use Authorization), determination of safety and need, and legality of employer or public health authority to make that determination. The requirement is likely to depend on whether the vaccine uptake in the population has reached sufficient levels (70-85%) for herd immunity to be assured, and the risk of disease, outbreaks, hospitalization, and death if this level of vaccination is not reached by next winter, when seasonal effects are likely to cause a resurgence of COVID-19.

Q. How many doses is the vaccine and how far apart?
A. Both the Pfizer and Moderna vaccines are two-doses. This means that you must receive both doses to achieve the 94-95% protection that was seen in the trials.

  • The Pfizer vaccine is two doses given 21 days apart
  • The Moderna vaccine is two doses given 28 days apart

Q. What if I get the first dose and then don’t want the next dose?
A. It is important to remember that the two large Pfizer and Moderna trials were not designed to assess the benefit from a single shot. For example, everyone in the Pfizer vaccine group received two shots, 21 days apart. Thus, for each vaccine participant, there were only 21 days between doses that provided any information about the effect of the first dose alone. 21 days is barely enough time for that dose to have its full immune effect. Thus, even though the overall data suggest that benefit may have started to be seen after the first dose, there is insufficient data in that time to make any conclusions. In addition, it is not known whether any benefit after the first dose will last without the second dose to lock in protection.

All that can be known from the scientific evidence is that two doses are needed to see the 94-95% protection. This is the reason why you should not start the vaccine series unless you intend to complete it. It is also important to anticipate that the COVID-19 vaccine often causes a mild flu-like illness after each dose. These symptoms do not mean that you have an infection or are sick with COVID-19. Instead, these vaccine-related symptoms are a sign that your body is working hard to build an immune response to protect you from future infection. Thus, developing these symptoms after the first dose does not mean you shouldn’t receive the second dose. You should expect similar symptoms after each dose. 

Q. What if I missed my second dose? Can I get it late?
A. Ideally, you should try to be on time with your second dose because the data on vaccine benefit from the clinical trials were based upon a fixed number of weeks between doses (3 weeks between Pfizer doses; 4 weeks between Moderna doses).  However, in real life, there may be reasons that prevent you from getting your second dose on time. All recommended vaccines have a window of 4-6 weeks that a dose can be given late without being considered delayed. Even beyond that time, you should still receive the second dose.

Q. Can I get my second dose a day or two early?
A. In both Pfizer and Moderna trials, participants were allowed to get their second dose up to two days early. Earlier than that is not recommended given the time needed for the first dose to take effect. In general, it is preferable for the second dose to be given on time or later. 

Q. What if I have been exposed to someone with COVID-19 close to the time of my scheduled dose? Should I reschedule?
A. If you have had a known exposure to someone with COVID-19 within 10-14 days of your scheduled dose, you should consider rescheduling to avoid being infected at the time of your dose. The risk of this is likely to be greatest with a household exposure or other conditions of prolonged close contact without masking. If this is the case and you are able to reschedule, it would be advisable to do so. If you are unable to reschedule, you can go ahead and receive your vaccine as long as you have no symptoms at the time of the vaccine. Just be aware that you may still develop COVID-19 around that same time and would need to be tested, and if tested, you will need to be quarantined. 

Q. What side effects do the vaccines have? Do I have to do any planning?
A. So far, clinical trials have shown that COVID-19 mRNA vaccines are highly protective and generate a strong immune response. Sometimes when vaccines produce an immune response, there may be side effects that feel like the flu, but do not mean you are infected or contagious. Instead, these symptoms are simply a sign that your body is successfully generating an immune response to provide you protection.

  • Expect some symptoms after vaccination. Both mRNA COVID-19 vaccines commonly cause mild-to-moderate non-infectious “flu-like” symptoms.
  • Pick a good time
    • Get your vaccine when you do not have anything important planned in the next day or two, including work shifts. This is more important after the second dose since symptoms are more common after the second dose.
    • If you can, have staff who have highly specialized skill sets separate their vaccines by at least 3 days in case one needs to miss work for vaccine-related side effects
  • Pfizer mRNA vaccine
    • Percent of people with any symptoms: 59% after 1st dose, 70% after 2nd dose

                  Note: in placebo (no vaccine) group: 47% symptoms after 1st dose, 34% after 2nd

    • Types of symptoms: fatigue 63%, headache 55%, muscle aches 38%, chills 32%, joint pain 24%, fever 14%
    • Percent of people with severe side effects: fatigue 4%, headache 2%
  • Moderna mRNA vaccine
    • Percent of people with any symptoms: 55% after 1st dose, 79% after 2nd dose

      Note: in placebo (no vaccine) group: 42% symptoms after 1st dose, 37% after 2nd

    • Types of symptoms: fatigue 69%, headache 63%, muscle aches 60%, joint pain 45%, chills 43%
    • Percent of people with severe side effects:
      • First dose: fatigue 1%, muscle aches 1%, joint pain <1%, headache 2%, chills <1%, fever <1%
      • Second dose: fatigue 11%, muscle aches 10%, joint pain 6%, headache 5%, chills 2%, fever 2%

Q. Should I plan to take Tylenol or Motrin before my vaccine dose?
A. If you regularly take aspirin, acetaminophen (e.g. Tylenol) or ibuprofen (e.g. Motrin, Advil) for other medical conditions, please continue to do so as directed by your physician or as needed. Otherwise, do not pre-medicate. In general, pre-medicating with over-the-counter medications that reduce fever or inflammation such as acetaminophen (e.g. Tylenol) and ibuprofen (e.g. Motrin, Advil) before receiving a vaccine may reduce its ability to work and can blunt your immune response to the vaccine. The time to take these over-the-counter medications is after you have symptoms that make you uncomfortable after vaccination. If you are uncomfortable, don’t hesitate to take an over-the-counter medication to help you feel better. If you usually take these medications for other medical reasons, continue to take them per your normal routine. 

Q. What ingredients are in the vaccines?
A. The Pfizer BioNTech COVID-19 vaccine includes the following ingredients: mRNA, lipids ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 2 [(polyethylene glycol)-2000]-N,N-ditetradecylacetamide, 1,2-Distearoyl-sn-glycero-3-phosphocholine, and cholesterol), potassium chloride, monobasic potassium phosphate, sodium chloride, dibasic sodium phosphate dihydrate, and sucrose.

The Moderna vaccine contains the following ingredients: mRNA, lipids (SM-102, 1,2-dimyristoyl-rac-glycero-3-methoxypolyethylene glycol-2000 [PEG2000-DMG], cholesterol, and 1,2-distearoyl-sn-glycero-3-phosphocholine [DSPC]), tromethamine, tromethamine hydrochloride, acetic acid, sodium acetate, and sucrose.

Q. If I have allergies to food or medication, should I worry about having an allergic reaction to the vaccine?
A. Allergies are generally linked to specific items. Having a significant allergy to a food or different medication does not necessarily mean that you are at higher risk for an allergic reaction to the COVID vaccine. The only definite reason to not give the COVID-19 vaccine to someone is if that person has a known allergy to the COVID vaccine (from prior doses) or an ingredient in the vaccine. For example, mRNA vaccines are not made in chicken eggs and there should not be any additional risk for people with allergies to eggs. For individuals who have a lot of serious allergies, please consult with your doctor. If you have been told to carry epinephrine (Epipen) for any reason, we recommend that you continue to do so, including when you receive the vaccination. All vaccination distribution centers are required to have emergency allergy medications on site, and the CDC is recommending that everyone who receives the vaccine be observed for 15 minutes, or 30 minutes if you have any history of anaphylaxis for any reason. If you are unable to wait that duration of time, we recommend that you remain around other people for the 15 minutes immediately after receiving the vaccine, or are on the phone with someone who is aware that you have just been vaccinated and knows your location. 

Q. Will my medication interfere with the vaccine?
A. There are no medications that are contraindications to the COVID-19 vaccine. In fact, we recommend that you take all your medications as prescribed to ensure your health is in the best condition before vaccination. Nevertheless, there are some special circumstances to consider:

  • If you are taking a blood thinner, check with your doctor if you are able to get a vaccine shot without a bleeding risk
  •  If you are on immunosuppressant medication or chemotherapy, check with your doctor about the best timing for you to receive your vaccine. If medication is taken in a periodic fashion, there may be better times in the cycle to be vaccinated than others.  

Q. What if I get COVID-19 after receiving my first dose? Is that dangerous?
A. As millions are vaccinated across the United States, some persons happen to become sick with COVID-19 before their two-dose vaccination sequence is complete. Remember, you do not reach the 95% protection seen in the clinical trials until 7 days after the second dose of the Pfizer vaccine, and 14 days after the second dose of the Moderna vaccine. Some people have been exposed to persons who have COVID-19 before or shortly after receiving the vaccine. If you become infected and have been vaccinated at the same time, your body will work to both fight the infection and respond to the vaccine by making more antibodies. You will likely experience the symptoms related to both, but the vaccine will still be working to help you make the right antibodies to prevent future infection. If your infection is close to your second dose, you will need to delay your dose if your symptoms started within 10 days of your appointment or if you have a fever within 24 hours of your appointment. After you are no longer infectious, you are able to receive your second dose. 

Some have suggested that a second dose may not be necessary in those who have been infected. However, it has not been proven that infection plus a single dose is equivalent to two doses of an effective vaccine in the long run. While it may be true for some select individuals, it is unlikely to be true for most or all individuals. Because it is not possible to know, the recommendation is that people who have had COVID-19 should still receive two vaccine doses. Two things are well understood at this time. First, that infection does not provide trustworthy immunity beyond 3 months. Second, two doses of the vaccine results in 95% protection in two large trials. 

Q. If I have had COVID-19, should I delay getting the vaccine? When is it safe to get it?
A. If you have had COVID-19, you can and should receive the vaccine when you are eligible. This can be as early as 10 days after your COVID-19 symptoms began if you have not had a fever for the past 24 hours. In general, if you have an opportunity to receive the vaccine, you should take advantage of the opportunity. However, you may choose to delay your vaccine for up to several weeks for the following reasons:

  • If you still don’t feel well enough to get a vaccine because you are still recovering from the effects of COVID-19
  • If there is vaccine shortage and you are certain you can schedule a dose within 2 months of your infection. Remember, it takes over a month to become protected by the two-dose vaccine series, and your infection only generates protection for about 3 months.

Q. What is Bell’s palsy or Guillain Barré? Do the COVID vaccines cause this?
A. Bell’s palsy is a temporary facial nerve paralysis that occurs in 40,000 people in the U.S. every year (110 people every day). Its cause is often unknown, but it is linked to stress and infection, including COVID-19. There were cases of Bell’s palsy among participants in the large clinical Pfizer and Moderna trials with a few more in the vaccine versus placebo group in both trials. However, the FDA did not determine that the vaccines were a cause of Bell’s palsy because the number of cases in the trials was less than the expected number of cases that would normally occur in the number of people in the trials over the time period of the trials.

Guillain Barré is a rare disorder that involves weakness and paralysis. It usually requires hospitalization and slow recovery with treatment. While Guillain Barré is rarely associated with the flu vaccine, it has not been associated with the COVID-19 vaccines. 

Q. Does the COVID vaccine cause cancer?
A. The COVID mRNA vaccines do not cause cancer. In fact, these types of vaccines have been used to treat cancer. The way these vaccines work is to provide an instruction set to make a protein. When used to treat cancer, mRNA vaccines use an instruction set to mimic proteins on the surface of cancer cells so that the body learns to recognize them as non-human and fight against them. In a similar way, the COVID vaccines make the COVID-19 spike protein and help the body make antibodies and fight against the virus. The vaccine is not alive and cannot infect or change our cells. 

Q. Does the vaccine cause infertility or affect our genes?
A. The vaccines do not cause infertility or affect any of our genetic code. The mRNA vaccines do not enter the part of the cell where DNA is housed, and do not and cannot affect our genetic material. In addition, the mRNA in the vaccine only stays in the body very briefly and is taken up by the cells in our arm. It does not move from the arm to the reproductive organs. During the vaccine trials when participants were asked to refrain from becoming pregnant, over 20 people who received the vaccine became pregnant during the trials, suggesting the vaccine does not cause infertility. If you are pregnant when you receive the vaccine, the mRNA does not cross the placenta. The only thing that crosses to the baby are the protective antibodies that your body makes in response to the vaccine. Many pregnant healthcare providers have chosen to receive the vaccine with no evidence of harm to the baby. 

Q. Does the vaccine cause me to be tracked? Does it inject a microchip?
A. The COVID-19 vaccines do not contain any tracking or surveillance device. The vaccines only contain clear liquid, and the ingredients are known. There is no microchip in the vaccine, and there is no such device that could fit through the tiny needle that is used to inject the vaccine. 

Q. Does the vaccine cause me to shed COVID-19 due to asymptomatic infection?
A. This is unlikely to happen. First, both Pfizer and Moderna trials are evaluating the likelihood of asymptomatic disease and more data will be known over time. Moderna already reported that asymptomatic disease was greatly reduced at the time of the second vaccine dose. At UCI Health, our healthcare providers are routinely offered asymptomatic testing for COVID-19, and we have similarly found a marked reduction in both symptomatic and asymptomatic disease after vaccination. Second, there is no carrier state for COVID-19. The virus does not sit in the throat or nose waiting to infect someone. Third, there is no precedent for a highly effective vaccine against a virus that prevents symptomatic, but not asymptomatic, disease. This has not been shown to occur. Importantly, the opposite has been shown with viral vaccines where breakthrough disease results in less shedding, even when infected.

Q.Is it better to wait to get the vaccine? What does waiting tell me?
A. When a vaccine is authorized for use, it is understandable that people may want to wait to see how the vaccine performs in others before they agree to get the vaccine themselves. For the Pfizer and Moderna vaccines authorized in the U.S., there were over 35,000 individuals in the combined trials who received the vaccines. These large trials helped define common side effects expected from the vaccines. Post-authorization use in more people has helped confirm these side effects and define increasingly rare events. Due to the pandemic, the scale of vaccine production and use reflects in a few weeks what other vaccines experience in several years. By early February 2021, over 32 million people in the U.S. have received these mRNA vaccines, and vaccination is progressing at approximately a million doses a day. In addition, over 15 million Pfizer and Moderna COVID-19 vaccines have been given in other countries worldwide. This experience has confirmed that severe allergic reactions are very rare, and side effects are mild and temporary. In contrast, by early February 2021, there were still 120,000 COVID cases diagnosed every day in the U.S.. The risk of COVID-19 hospitalization, death, and post-infectious chronic fatigue, confusion, and pain far outweighs the minor side effects of the vaccine, with millions and millions of people experiencing safe and effective vaccination and the reassurance of 95% protection from COVID-19.