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 February 2021, the COVID-19 pandemic caused 100 million confirmed infections and 2.2 million deaths worldwide. In the United States, 26 million people have been infected with COVID-19 and nearly 500,000 people have died. This winter, 3,300 U.S. lives were lost every day to a surge of COVID-19 infections. These striking numbers underestimate the actual spread of the virus because only people who have been tested are counted.

Widespread use of safe and effective COVID-19 vaccines will end the pandemic when 70% to 85% of people are vaccinated, experts believe. The fact that we have safe and highly protective vaccines should lead us all to want to be vaccinated.

UCI Health infectious disease experts provide answers to the following questions people have asked about the vaccines.

Download our COVID-19 vaccine FAQ ›

View the FAQ in Spanish ›


Why Vaccinate? Which Vaccine? What’s in the Vaccine?

Q-1. Why should I get a COVID-19 vaccination?
A. By preventing infection, COVID-19 vaccines not only saves lives, they also also prevent long-lasting health problems reported after infection. They include fatigue, shortness of breath, cough, joint pain, chest pain, difficulty thinking and concentrating ("brain fog"), depression, muscle pain, headache and intermittent fever. Some COVID-19 patients also have reported problems with their heart, lungs, kidneys, skin, teeth and nervous system.

Q-2. Should I get the vaccine now or wait?
A. With 100 million cases of COVID-19 worldwide and 26 million U.S. cases reported, we cannot wait to be vaccinated. More than 30 million U.S. doses of the Pfizer and Moderna mRNA vaccines already been given 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 families and friends — should die from COVID-19.

In fact, we should be urgently vaccinating as many people as possible because being vaccinated enables us to protect our workplaces and our close circle of friends and family. The sooner 70% to 85% of us are vaccinated, the sooner the pandemic will come to an end.

Q-3. What COVID-19 vaccines are currently available?
A. Vaccines can only be licensed in the United States if they have strong safety and effectiveness data from clinical trials. Several COVID-19 vaccines do have such data from well-designed large clinical trials. The table below lists COVID-19 vaccines that are already authorized for U.S. use or are likely to seek U.S. authorization in the future. The Pfizer and Moderna vaccines, which have both demonstrated an incredibly high level of protection (up to 95%) in large clinical trials, are now being given to millions of Americans.

None of the other vaccines have yet proven to give better protection than these mRNA vaccines. All vaccines listed in the table require two doses for full effect, except for the single-dose Johnson & Johnson vaccine, which has been shown to provide 72% protection.

COVID-19 Vaccines Authorized or Likely to Seek U.S. Authorization (as of February 2021)





Trial Size






95% 1


Yes (16+)




94% 2


Yes (18+)




89% 3



Johnson &

Adenovirus vector (DNA)






Adenovirus vector (DNA)





Green = authorized for U.S. use
1 Polack FP et al NEJM 2020; 383(27): 2603-15
2 Baden LR et al. NEJM Dec 30, 2020 (online)
3 30,000 patient trial pending

Q-4. What is in the vaccine? What is an mRNA vaccine?
A. The two vaccines authorized for U.S. use are both mRNA vaccines — mRNA stands for "messenger ribonucleic acid," which instructs the body to make proteins. Every cell in our bodies has mRNA in it because we need proteins to survive. The mRNA in the Pfizer-BioNTech and Moderna COVID-19 vaccines instruct your body to make a specific protein — the spike protein — found on the surface of SARS-CoV-2, the virus that causes COVID-19. When your body makes this viral protein, it is recognized as not human, triggering your body to develop antibodies to fight it. These antibodies protect you if you encounter the virus later.

Some vaccines for other diseases inject the viral protein itself, but mRNA vaccines inject only the instructions needed for your body to make the protein. After making the protein, your body eliminates mRNA. The messenger RNA is temporary and cannot mix into your genetic code. The COVID-19 vaccines are not the first successful mRNA vaccines. Many have been made to combat the flu, rabies, CMV (cytomegalovirus) and Zika viruses. (See Question 30 to learn the complete ingredients of the mRNA vaccines.)

Q-5. Can the COVID-19 vaccine give me COVID? Is there live virus in the vaccine?
A. None of the currently developed COVID-19 vaccines involve live SARS-CoV-2 virus. The mRNA vaccines are not alive and cannot give you or anyone else COVID-19. The vaccine does not make you contagious.

Q-6. Should I worry that the vaccine was made so quickly? Were steps skipped?
A. No steps were skipped. All the COVID-19 vaccines being distributed in the United States were either helped by government funds (e.g., Operation Warp Speed) or were funded by large companies, or both. These funds helped speed the process in three ways:

  • Trial enrollment: By increasing the number of people recruiting patients, more people can be enrolled in a trial in a shorter time period. For example, one person can recruit 1,000 people into a trial, but 1,000 recruiters can recruit 1,000 trial participants. The funds helped the vaccine trials quickly enroll tens of thousands of participants.
  • Manufacturing: Funding helped increase the number of manufacturing plants, warehouses and employees. In addition, mRNA vaccines are fast to manufacturer because they don’t involve the need to grow a virus to produce virus proteins needed for the vaccine. For example, some flu vaccines require a step require the vaccine protein to be made from live virus grown in chicken eggs. The COVID-19 vaccines do not involve any live virus. They are created with molecular techniques and can be rapidly manufactured.
  • Distribution: Once produced, funding enables vaccines to be shipped rapidly around the nation and the world on a regular basis.

Q-7. What is the difference between Emergency Use Authorization (EUA) status for a vaccine and full Food and Drug Administration (FDA) approva?
A. When an vaccine has demonstrated effectiveness in a clinical trial, its maker can apply for EUA status two months after the publication of trial safety data. Six months of post-vaccine safety data must be provided to apply for full FDA approval. The agency is encouraging the companies that have receive EUA status to apply for full approval as soon as possible. To date, both mRNA vaccines have reported outstanding safety data with no serious side effects.

Q-8. Who pays for the vaccinations?
A. The mRNA vaccines are free because the U.S. government has purchased millions of doses. Your health insurance may be charged an administrative fee to cover the cost of the people who give you the vaccine. If you do not have insurance, the administration fee will be covered by the federal government.

How Well Do the Vaccines Work?

Q-9. How well does the vaccine work? Should I get Pfizer or Moderna?
A. The Pfizer and Moderna COVID-19 vaccines were both tested in large trials involving tens of thousands of participants who were randomized to receive the vaccine or a placebo injection. They were allowed to live their lives and mix with their communities as they normally would. Since the trial is randomized, large numbers help ensure that the type of human interactions in one group are similar in the other. The trials reported a remarkable 94% to 95% efficacy in preventing COVID-19 cases among those who received the vaccines. A 95% efficacy rate means the vaccinated group had only 5% of cases seen in the placebo group. For example, if the non-vaccine group had 100 cases of COVID-19, the vaccine group would only have five. As important, the vaccine not only prevented COVID-19 infections overall, it also prevented severe COVID-19 cases.

Protection was measured after the second dose for both vaccines. Pfizer studied the amount of protection seven (7) days after the second dose, while 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

Which vaccine is better? The trials show that both mRNA vaccines are extremely effective. Made by two different companies and tested in separate large clinical trials, both were found to be 95% protective. Nearly identical results from two completely different large trials is the best result scientists could hope to see.

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


  • Ages 16-55: 96% efficacy
  • Over age 55: 94% efficacy


  • Ages 18-64: 96% efficacy
  • Ages 65 and older: 86% efficacy

Trial results were submitted in full to the FDA, shared with the Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP), and published in the New England Journal of Medicine for the Pfizer and the Moderna vaccines.

Q-10. Am I protected as soon as I receive the vaccine? Can I stop wearing a mask?
A. No. The protection was measured starting seven (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. Even after that period, 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. COVID-19 cases are still widespread in our community. With 95% protection, you can still get COVID-19, especially if many people around have the virus. Experts believe that 70% to 85% of the population must be vaccinated before the pandemic will be over.

Q-11. After I'm vaccinated, can I still spread COVID-19 to my friends and family? Or be an asymptomatic carrier passing the virus to others?
A. Although the vaccine is 95% protective, there is a 5% risk of infection. This 5% risk can be important when many people in a community have COVID-19. If you develop symptoms of COVID-19, you should get tested. If you test positive, you are likely contagious to others. Fortunately, we have evidence from other vaccines (measles, for example) to indicate that vaccination may make you less contagious to others if you do become infected.

It is unlikely that a person who has been vaccinated would be an asymptomatic carrier. First, both Pfizer and Moderna are continuing to track trial participants and evaluate the likelihood of asymptomatic disease. More data will be available over time. However, Moderna already has 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.

Q-12. 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 whether protective levels of antibody are still present. This means more will be known over time. Since we know that immunity to other coronaviruses lasts one to three years, we anticipate that the COVID-19 vaccine will be needed annually, possibly every other year at best. Annual vaccinations may also help address any variants of the virus because the vaccines can be modified each year, as is done now for the influenza vaccine. The Pfizer and Moderna vaccines require two doses, but it is likely that an annual vaccine would be a single dose.

Q-13. What do I need to know about variants to the virus that causes COVID-19?
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 that now have spread throughout the world. We are able to find these variants because we can sequence the virus’ genetic code. There are several concerns about the variants, including whether some are better at infecting people, spreading between people or causing severe disease and death. One of the most important concerns about these variants is whether the current vaccines will work on all of them.

Much media attention has been given to whether a variant might evade a vaccine. Certain information is more helpful in determining 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 variants that have emerged in the United Kingdom and South Africa.

Evaluating the usefulness of information about variants and vaccine failure

Type of Information

Value for Proving Vaccine Failure

Can cause outbreaks


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.

Variants of the SARS-CoV-2 virus appear as more and more people become infected and the virus creates mutations. The best way to stop the spread of variants is to vaccinate as many people as quickly possible to stop the spread and growth of the virus.

Q-14. Were different ethnic and racial groups included in the vaccine trials?
A. Both mRNA vaccine trials reported the distribution of race and ethnicity:


  • Non-white racial groups: 10% Black; 4% Asian; 3% other
  • Hispanic/Latinx: 26%


  • Non-white racial groups: 10% Black; 5% Asian, under 3% other
  • Hispanic/Latinx: 20%

All vaccines are designed 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 known vaccine for which different ones are recommended based upon race or ethnicity.

Q-15. 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. The vaccine will, however, cause you to test positive on certain antibody tests (also called serology) that look for antibodies against the spike protein since the COVID-19 vaccines help build these antibodies to the virus.

Who Should Get Vaccinated?

Q-16. 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-17. I already had COVID-19. Do I need 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 had COVID-19 received monoclonal antibodies or convalescent sera to help prevent severe disease. If you have had this antibody therapy, you should not receive the vaccine until at least 90 days from the time you received the treatment because those antibodies can bind the spike protein produced by the vaccine and prevent your body from making its own protective antibody.

Q-18. Should pregnant, breastfeeding or immunocompromised persons get the vaccine?
A. Initial vaccine trials usually do not enroll women who are pregnant, attempting to become pregnant or breastfeeding, or immunocompromising people and those taking medications that depress the immune system. However, even though these groups of people were not enrolled in the Pfizer or Moderna mRNA trials, we do know that pregnant or immunocompromised persons are at higher risk for developing serious COVID-19 disease. That is why people with these conditions may want to receive the vaccine.

Women who are pregnant, breastfeeding or trying to become pregnant, should consider the following factors in deciding whether to get vaccinated:

  • Consider your personal risk for becoming infected with COVID-19 given the number of cases in your community, as well as your usual level of interaction with family, friends and others in that community.
  • Second, in general, concern for the effects of any potential medication on a developing fetus usually are related to the first trimester when organs are forming.
  • 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 vaccine trial data can be used to provide a recommendation for protection or safety, at least 36 participants in the mRNA trials became pregnant during the trials, including 18 in the vaccine group. These women are being monitored for any effects.
  • The American College of Obstetricians and Gynecologists has recommended that COVID-19 vaccines be offered to pregnant and breastfeeding women, and opposed requiring women of childbearing age to have a pregnancy test before receiving the vaccine.

When weighing whether immunocompromised individuals should be vaccinated, safety is not the concern but rather that the vaccine may not generate as strong a protective response as in someone with a healthy immune system. But even a partial response may be an important benefit, given that immunocompromised people are at greater risk from COVID-19. For example, the American Society of Transplantation recommends that all transplant patients and members of their household get the COVID-19 vaccine when it becomes available.

For both groups, it is important to discuss your preferences and options with your doctor.

Q-19. When will children be eligible for vaccination?
A. The Moderna and Pfizer vaccines are now authorized only for adults (age 18 and older for Moderna, age 16 and older for Pfizer). Trials for both vaccines are underway in children age 12 and older that are expected to be completed this summer. If successful, authorization to vaccinate those age groups could come by summer or fall 2021. This summer, trials for children under age 12 are expected to begin and would take several months to complete. Vaccination is unlikely to be available for most school-age children before school begins in the fall. For this reason, it is even more important that parents and other adults be vaccinated to provide protection for children. It also means that infection-prevention strategies will still be important for school-age children until a safe and effective vaccine is available for them.

Q-20. Who has priority to get the vaccine?
A. As of early February 2021, the following groups are eligible to receive COVID-19 vaccinations in Orange County:

  • Healthcare personnel (e.g., staff at hospitals, nursing homes and other care facilities)
  • Residents of long-term care facilities
  • People ages 65 and older

We anticipate that essential workers in education, childcare, food services and agriculture will soon be added to that list. We also expect that younger age groups will become eligible. With vaccines now being sent to major U.S. pharmacy chains, the COVID-19 vaccine is likely to be widely available to any adult who wants it by mid-April.

Q-21. How many doses are arriving in 2021? Where can I get vaccinated?
A. The U.S. supply of COVID-19 vaccines will increase greatly in coming months. Pfizer provided 29 million U.S. doses in 2020, and will provide 200 million more by May 2021. Moderna will provide 100 million doses by the end of March and another 100 million doses by the end of June.

This means vaccines will become increasingly available, including at local Orange County pharmacies. People in eligible groups will soon be able to obtain the vaccine through their medical provider or at Orange County public health super sites by registering through the Othena app.

Q-22. Will the COVID-19 vaccine be required?
A. A variety of vaccines for measles, mumps, rubella, chickenpox and polio are now required in certain settings — elementary and high school, college and many healthcare facilities. Last year, the University of California required the flu vaccine for all its campuses. Requiring COVID-19 vaccinations also depends on several factors, including obtaining full FDA approval, determination of safety and need, and the legality of employer or public health authority making such a determination. It may also be contingent on vaccine uptake in the population reaching sufficient levels (70% to 85%) for herd immunity to be assured, or weighing the risk of disease, outbreaks, hospitalization and death if that level of vaccination is not achieved by winter, when colder weather is likely to cause a resurgence of COVID-19.

Timing of Doses?

Q-23. How many vaccine doses are needed and how far apart?
A. Both the Pfizer and Moderna vaccines are a series of two doses and you must get both doses to achieve the 94% to 95% protection seen in clinical trials.

  • The Pfizer vaccine doses are given 21 days apart
  • The Moderna vaccine doses are given 28 days apart

Q-24. What if I get the first dose and then don’t want the next dose?
A. The scientific evidence indicates that two doses are needed to get 94% to 95% protection. You should not start the vaccine series unless you intend to complete it.

The two large trials were not designed to assess the benefit from a single shot. Everyone in the Pfizer vaccine group received two shots, 21 days apart. For each vaccine participant, there were only 21 days between doses to derive any information about the effect of the first dose alone, and 21 days is barely enough time for a single dose to provide its full immune effect. While the overall data suggest that participants may have seen a benefit after the first dose, data are insufficient to draw any conclusions. It also is is not known whether any benefit after the first dose will last without the second dose to lock in protection.

It is 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 building an immune response to protect you from future infection. Developing these symptoms after the first dose does not mean you should forego the second dose. You should expect similar symptoms after each dose.

Q-25. What if I missed my second dose? Can I get it late?
A. Ideally, you should get the second dose at the recommended interval. The data on vaccine benefit from the clinical trials were based on a fixed number of weeks between doses (three weeks between Pfizer doses; four weeks between Moderna doses). However, there may be reasons that prevent you from getting the second dose on time. All recommended vaccines have a window of four to six weeks for a dose to be given without being considered late. Even if you are delayed beyond that time, you should still receive the second dose.

Q-26. Can I get the second dose a day or two early?
A. Participants in both the Pfizer and Moderna trials 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 full effect. In general, it is preferable for the second dose to be given on time or later.

Q-27. 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 been exposed to someone with COVID-19 within 10 to 14 days of your scheduled dose, 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 prolonged close contact without masking. If this is the case and you are able to reschedule, it is advisable to do so. If you are unable to reschedule, get your vaccine as long as you have no symptoms at the time of vaccination. Be aware that you may still develop COVID-19 and would need to be tested and quarantined if you test positive.

Safety & Side Effects

Q-28. 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.

When scheduling your vaccine, consider that some symptoms are common after vaccination. Both mRNA COVID-19 vaccines can cause mild-to-moderate flu-like symptoms, so you may want to get your vaccine when you don't have important plans for the following day or two, including work shifts. This is more important after the second dose since symptoms are more common afterward. If you are scheduling vaccines for staff members, consider separating vaccinations for those with highly specialized skill sets by at least 3 days in case one person needs to miss work for vaccine-related side effects.

Here is what the trial data show:

Pfizer vaccine

  • Percent of people with any symptoms: 59% after 1st dose, 70% after 2nd dose
  • 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%
  • In placebo group: 47% symptoms after 1st dose, 34% after 2nd

Moderna mRNA vaccine

  • Percent of people with any symptoms: 55% after 1st dose, 79% after 2nd dose
  • 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%
  • In placebo group: 42% symptoms after 1st dose, 37% after 2nd

Q-29. Should I plan to take Tylenol or Motrin before my vaccine dose?
A. If you regularly take acetaminophen (e.g., Tylenol), ibuprofen (e.g., Motrin, Advil) or aspirin for other medical conditions, please continue to do so as directed by your physician or as needed. Otherwise, do not pre-medicate before getting the vaccine. In general, taking these over-the-counter medications that reduce fever or inflammation before receiving a vaccination may reduce its ability to work and blunt your immune response to the vaccine. The time to take these medications is after the vaccination when you have symptoms that make you uncomfortable. If you do have symptoms, don’t hesitate to take an over-the-counter medication to help you feel better. However, if you usually take these medications for other medical reasons, continue to take them per your normal routine.

Q-30. What ingredients are in the vaccines?
A. The Pfizer vaccine contains: 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: 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-31. 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 not to give the COVID-19 vaccine is when a person has a known allergy to the COVID-19 vaccine (from prior doses) or to an ingredient in the vaccine. For example, because mRNA vaccines are not made in chicken eggs, there should not be any additional risk to people with allergies to eggs. Individuals who have many serious allergies should consult their doctor. If you have been told to carry epinephrine (Epipen) for any reason, you should 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 recommends observing for 15 to 30 minutes anyone who has a history of anaphylaxis. If you are unable to wait that duration of time, you should remain around other people for 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-32. 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-33. What if I get COVID-19 after receiving my first dose? Is that dangerous?
A. As millions of people have been vaccinated across the United States, some have become infected with COVID-19 before their two-dose vaccination sequence was completed. Remember, you do not reach the 95% protection level seen in the clinical trials until seven (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 individuals with 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 both to fight the infection and respond to the vaccine by making more antibodies. You will likely experience symptoms related to both, but the vaccine still is working to help you make the right antibodies to prevent future infection. If you become infected within 10 days of your scheduled second dose or have a fever within 24 hours of your appointment, you will need to delay the second vaccination. Once you are no longer infectious, you may receive your second dose.

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

Q-34. 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 two (2) months of your infection. It takes more than a month to become fully protected by the two-dose vaccine series, and your infection only generates protection for about three (3) months.

Q-35. What is Bell’s palsy or Guillain Barré? Do COVID vaccines cause this?
A. Bell’s palsy is a temporary facial nerve paralysis that occurs in 40,000 people in the United States every year (110 people a day). Its cause is often unknown, but it has been linked to stress and infection, including COVID-19. Cases of Bell’s palsy occurred among participants in the large clinical Pfizer and Moderna trials and 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 recovery is slow. While Guillain Barré is rarely associated with the flu vaccine, it has not been associated with the COVID-19 vaccines.

Vaccine Myth Busters

Q-36. Does the COVID vaccine cause cancer?
A. The COVID mRNA vaccines do not cause cancer. In fact, these types of mRNA vaccines have been used to treat cancer. When used to treat cancer, mRNA vaccines use an instruction set to create proteins that mimic those on the surface of cancer cells to teach the body to recognize them as non-human and attack them. In a similar way, the COVID-19 vaccines make the virus' spike protein to help the body make antibodies will fight the virus. The vaccine is not alive and cannot infect or change your cells.

Q-37. Does the vaccine cause infertility or affect our genes?
A. The mRNA vaccines do not cause infertility and cannot affect your genetic material because they do not enter the part of the cell where DNA is housed. In addition, the mRNA in the vaccine stays in the body very briefly. It is taken up by the cells in our arm but does not move from the arm to the reproductive organs. During the vaccine trials when participants were asked to refrain from becoming pregnant, more than 20 vaccinated people became pregnant, suggesting the vaccine does not cause infertility. If you are pregnant when you receive the vaccine, the mRNA cannot cross the placenta. The only thing that crosses to the baby are protective antibodies your body makes in response to the vaccine. Among many pregnant healthcare providers who have chosen to receive the vaccine, there has been no evidence of harm to the baby.

Q-38. 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 contain only clear liquid and the ingredients are known (see Question 30). 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-39. Does the vaccine cause me to shed COVID-19 due to asymptomatic infection?
A. This is unlikely to happen. Both Pfizer and Moderna trials are evaluating the likelihood of asymptomatic disease and more data will be known over time, but Moderna already has 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.

In addition, there is no carrier state for COVID-19. The virus does not sit in the throat or nose waiting to infect someone. There is no precedent in other highly effective vaccine that prevents symptoms of a disease but not asymptomatic disease. In fact the opposite has been shown with viral vaccines, where breakthrough disease results in less viral shedding, even when infected.

Q-40. Is it better to wait to get the vaccine? What can I learn by waiting?
A. When a vaccine is authorized for use, it is understandable that people may want to see how the vaccine performs in others before they agree to be vaccinated. In both the U.S. Pfizer and Moderna vaccine trials, a total of more than 35,000 participants received the vaccines. These large trials helped define common side effects expected from the vaccines. The vaccines' release and use in more people has helped confirm these side effects and define increasingly rare events. In this pandemic, the scale of vaccine production and usage in a few weeks provides data that takes several years to gather for other vaccines. By early February 2021, more than 32 million U.S. people have received these mRNA vaccines and vaccination is progressing at about one (1) million doses a day. In addition, more than 15 million Pfizer and Moderna vaccines have been given in other countries worldwide. This experience has confirmed that severe allergic reactions are very rare and that side effects are mild and temporary.

Yet in early February 2021, more than 120,000 U.S. COVID-19 cases were being diagnosed every day. The risk of COVID-19 hospitalization, death and post-infectious chronic fatigue, confusion and pain far outweighs the minor side effects of the vaccine for the many millions of people getting safe and effective vaccination and the reassurance of 95% protection from the virus.