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COVID-19 vaccine FAQ

Back to vaccines

Last updated March 15, 2024

Available languages: Español

 

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Top 10 most frequently asked questions

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#1 Where can I get a COVID-19 vaccine? 
#2 How do we know that the vaccines are safe?
  • COVID-19 vaccines have gone through the most intense safety monitoring in U.S. history. 
  • The 2023-2024 COVID-19 vaccines use the same proven, Nobel prize-winning technology as the vaccines that hundreds of millions of people have already safely received. Like the seasonal flu vaccine, the COVID-19 vaccine gets updated to protect against common strains of the virus.
  • Tens of thousands of people volunteered to help test the vaccines in clinical trials. These clinical trials showed that the vaccines are safe and work well. The vaccines met the Food and Drug Administration’s (FDA) rigorous scientific standards for safety, effectiveness, and quality.
  • Learn more about vaccine safety.
#3 Do I need more than one dose of a 2023-2024 COVID-19 vaccine?
#4 Can I get a COVID-19 vaccine at the same time as my annual flu vaccine?
#5 Is it safe to get the vaccine if I am pregnant, breastfeeding, or planning a pregnancy?
  • Yes. Getting a COVID-19 vaccine is the best way to protect yourself.
  • Pregnant people are more likely to get very sick if they become infected with COVID-19. Getting sick with COVID-19 can lead to serious pregnancy complications, including premature birth and complications that can result in death.
  • COVID-19 vaccines are safe for pregnant people and people who are trying to become pregnant, as well as breast/chest feeding people and their children. The vaccines help keep you from getting sick. They are not associated with an increased risk of miscarriage, preterm delivery, stillbirth, or birth defects.
  • Learn more about COVID-19 vaccines during pregnancy and vaccines in general during pregnancy.

#6 Is the vaccine still free?
  • Coloradans can get the COVID-19 vaccine for low or no cost through their health insurance or a federal vaccine program.
  • Most insurance providers cover COVID-19 vaccines at no cost to you.
  • If your health insurance plan does not cover COVID-19 vaccines completely, you are considered underinsured. 
  • If you are underinsured or do not have health insurance, you qualify for a federal vaccine access program. You can go to a provider enrolled in a federal vaccine access program to get a COVID-19 vaccine at low or no cost. Federal vaccine access programs include Vaccines for Children and the Bridge Access Program.
    • While these providers may ask you for the following, you do not need to provide them in order to receive a publicly funded vaccine: 
      • Health insurance. 
      • A government-issued identification card. 
      • A social security card or number. 
      • An out-of-pocket fee for the administration of the vaccine.
    • It is illegal for the clinic to deny you a publicly funded vaccine for not showing documents or paying a fee.
    • Learn more about your right to get a publicly funded vaccine at low or no cost.
#7 Do I need to be a U.S. citizen to get a vaccine? 
#8 How were the 2023-2024 vaccines developed so quickly? 
  • Just like the virus evolves, so does the vaccine. It is common practice to adapt vaccines to target new strains of a virus, as we do every year with the flu vaccine. 
  • The FDA worked closely with the vaccine manufacturers to ensure the development of these newly updated vaccines was done safely and efficiently.
  • The 2023-2024 vaccines run on the same trusted technology as the earlier formulations of Pfizer and Moderna’s COVID-19 vaccines. 
  • Similar to the yearly flu vaccine, Pfizer and Moderna’s vaccines were updated to target the strains of COVID-19 that are currently circulating in the United States.
  • Updating an existing vaccine takes much less time than developing a new vaccine. Scientists already knew a lot about how mRNA vaccines work in the real world, and could apply that knowledge to making vaccines that better protect against current variants.
#9 Can children get a COVID-19 vaccine?
#10 What should I do if I lose my vaccine record?
  • If you got the COVID-19 vaccine in Colorado, you have two options:
  • If you got your COVID-19 vaccination(s) outside of Colorado, please contact your vaccination provider or the immunization information system of the state in which you received your COVID-19 to request a copy of your records.
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Getting a COVID-19 vaccine

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What types of COVID-19 vaccines are available? 
  • Vaccines made by Pfizer, Moderna, and Novavax are currently available in the United States. All three types of COVID-19 vaccines have been updated for the 2023-2024 respiratory season.
  • The Pfizer and Moderna vaccines are available for people aged 6 months and older. The Novavax vaccine is available for people aged 12 years and older. 
  • None of the updated 2023-2024 COVID-19 vaccines is preferred over another.
  • A vaccine made by Johnson & Johnson was available for some adults age 18 and older, but is no longer available in the United States now that all remaining doses have expired.
  • CDC has detailed information about each vaccine on their Overview of COVID-19 Vaccines page.  
How many doses of the COVID-19 vaccine do I need?
  • Most people need just one dose of an updated 2023-2024 COVID-19 vaccine to be up to date. It doesn’t matter how many doses of previous COVID-19 vaccines you received.
  • Adults aged 65 years and older should receive one additional dose of a 2023-2024 COVID-19 vaccine at least four months after their first dose of a 2023-2024 COVID-19 vaccine. 
  • People with weakened immune systems and children aged 6 months through 4 years may also need more than one dose of the updated vaccine depending on their vaccination history.
  • People aged 12 years and older who have not been previously vaccinated and choose Novavax need two doses to be up to date.
  • Talking with a health care provider can help you learn more about how many doses you or your child need and when to schedule them, but it’s not required. 
  • Learn more on CDC’s Stay Up to Date with COVID-19 Vaccines webpage.
How do I know what kind of vaccine I’ve received in the past?
Does my updated vaccine need to be the same brand as my previous vaccines?
  • Most people aged 12 years and older can get any updated 2023-2024 COVID-19 vaccine. It doesn’t matter what kind of vaccines you received in the past.
  • Children aged 5 through 11 years can get either Pfizer or Moderna’s 2023-2024 COVID-19 vaccine. It doesn’t matter what kind of vaccines they received in the past.
  • Children aged 6 months through 4 years should receive the same brand of vaccine for all their doses when possible. Talking with your child’s health care provider can help you learn more about which vaccine they should get, but it’s not required.
Why do I need another COVID-19 vaccine if I have already been vaccinated?
  • Staying up to date with your COVID-19 vaccines gives you the highest level of protection from severe illness, hospitalization, Long COVID, and death. 
  • Just like the virus evolves, so does the vaccine. All viruses mutate over time, including COVID-19. The spike-shaped proteins that cover the COVID-19 virus have changed since the original and omicron COVID-19 vaccines became available. These proteins were the original target of the COVID-19 vaccines, which is one reason why immunity from the original and omicron vaccines doesn’t protect as well against currently circulating variants. 
  • Getting an updated 2023-2024 vaccine gives targeted protection from the COVID-19 variants circulating right now. The newly updated vaccines teach your body to recognize the spike proteins that cover the XBB sub-variants of the virus. Studies show that the 2023-2024 vaccines help the immune system better fight these current variants compared to previous COVID-19 vaccines.
Can I get an updated COVID-19 vaccine if I was first vaccinated outside of the United States?
  • Yes. Everyone aged 6 months and older should receive at least one dose of an updated 2023-2024 COVID-19 vaccine regardless of past COVID-19 vaccination history.
  • You should get your updated vaccine at least two months after your most recent dose.
Should I get vaccinated if I’ve already had COVID-19?
  • Yes. COVID-19 vaccination is recommended for everyone 6 months of age and older, even if you’ve already had COVID-19, as long as it’s been at least two months since your most recent dose of an earlier COVID-19 vaccine. 
  • People who recently had COVID-19 and are not immunocompromised or at high risk may consider waiting up to three months after they tested positive or first started feeling symptoms to receive their next dose. Talking with a health care provider can help you learn more about the best time to schedule your next dose, but it’s not required.
  • While recovering from COVID-19 may give you some immunity to the virus, the immunity might not last more than a few months. It’s possible to get COVID-19 again even if you have already recovered from the illness. You should plan to get vaccinated with all recommended doses to make sure you have the best possible protection from COVID-19.
  • Data show that people who previously had COVID-19 and also got vaccinated were better protected from hospitalization than people who only had immunity from a previous infection.
  • It is safe to get a vaccine as soon as you feel better. 
Should I get vaccinated if I recently received plasma treatment for COVID-19?
  • Yes, people who previously received convalescent plasma as part of COVID-19 treatment can be vaccinated at any time. COVID-19 vaccination does not need to be delayed following receipt of convalescent plasma.
Is it safe to take my prescription medications on the same day I get vaccinated? 
  • Yes, it is fine to take all prescription drugs as usual. 

Should I take over-the-counter medication like Tylenol or Advil before getting vaccinated to help with the side effects? 
  • Avoid taking over-the-counter pain or fever medications before getting vaccinated. There is a theoretical possibility that doing so might reduce vaccine effectiveness. 
  • If it is normally safe for you to do so, you can take over-the-counter pain or fever medication after you receive the vaccine if you start to feel side effects.  
Can I get the COVID-19 vaccine at the same time as other vaccines?
  • Yes. COVID-19 vaccines and other vaccines may now be given at the same time, if needed, or close together. 
  • Your doctor may consider the types of vaccine, whether you are behind on recommended vaccines, and what kind of side effects the vaccines may have before deciding whether or not to give them together. Talk to your doctor about additional concerns you might have about getting more than one vaccine at the same time. 
Can I get the vaccine at my doctor’s office or local pharmacy? 
  • Many pharmacies, doctor’s offices, and other locations offer COVID-19 vaccines. Contact your health care provider for more information. 
  • Visit vaccines.gov or call 1-800-232-0233 to find vaccine appointments near you.
I need a ride to my vaccine appointment. What are my options?

Mile High United Way’s Ride United program provides access to free rides (up to 25 miles each way) to vaccination sites across Colorado. Dial 2-1-1 or visit 211colorado.org to learn more.

What should I do if I’m asked to pay for the vaccine?
  • Most health insurance plans cover COVID-19 vaccines with no copay or coinsurance. If your health insurance plan does not cover COVID-19 vaccines completely at no cost to you, you are considered underinsured. 
  • Underinsured and uninsured Coloradans can go to a provider enrolled in a federal vaccine access program to get an updated COVID-19 vaccine at low or no cost. These include the Vaccines for Children and Bridge Access programs.
    • People with insurance plans that do not cover the entire cost of the COVID-19 vaccine must present at an in-network Bridge Access provider to be eligible for a low or no cost COVID-19 vaccine.
  • Colorado law makes sure that uninsured and underinsured people can receive publicly funded vaccines even if they cannot pay an administration fee. 
  • A provider enrolled in one of these programs may ask you for an out-of-pocket fee for the administration of the vaccine, but cannot deny you a vaccine if you cannot afford to pay the fee.
  • Learn more about your right to get a publicly funded vaccine at no cost.
How much of my personal information will I need to share to get the vaccine? 
  • Like other routine vaccinations, you will need to share some personal information with your vaccine provider when you get a COVID-19 vaccine. This may include your name, date of birth, and contact information. Your privacy is a top priority, and your information will not be used for anything other than vaccine administration and follow-up information about the vaccine. 
  • Sharing your identity and some of your medical history ensures that the vaccine is administered safely, effectively, and responsibly. Your individual immunization records are confidential, personal medical information, and public health will never share them publicly. 
  • The state health department maintains the Colorado Immunization Information System (CIIS), a confidential, population-based, secure computerized system that collects and consolidates individual-level vaccine and exemption data for Coloradans of all ages from a variety of sources. Health care providers have limited access to CIIS based on their need to input and access data for their patients. 
  • Under Colorado law, you can choose to remove your immunization information from CIIS at any time. This is called an opt-out. 
  • Read the Colorado Immunization Information System privacy policy.
  • The state health department submits monthly, anonymous COVID-19 vaccine administration data to the CDC as required. The state works to ensure that no personally identifiable information like your name or full address will be shared with CDC.  
Do I need government-issued identification to prove my age, address, or name?
  • It depends on where you get vaccinated.
  • COVID-19 vaccine providers who get their vaccines from the commercial market can require identification from you.
  • Some COVID-19 vaccine providers get their vaccines from the federal government through the Vaccines for Children and Bridge Access programs. Underinsured and uninsured Coloradans can get COVID-19 vaccines at low or no cost from these providers. 
    • These providers may ask you for identification, but they cannot deny you a vaccine for not showing it.
  • Learn more about your right to get a publicly funded vaccine without needing to show identification.
Do I have to be a resident of Colorado to get vaccinated?
  • No. You do not need to be a resident of Colorado, nor of a particular Colorado county, to be vaccinated in Colorado. 
Should I take a test to see if I am infected before getting the vaccine?
  • No. The CDC does not recommend getting tested before getting the vaccine. If you do not have any symptoms and have not been recently exposed to COVID-19, there is no need to get a test before your vaccine appointment.
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Vaccine side effects

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What are the side effects of the vaccines? 
  • You may experience mild to moderate side effects after receiving the vaccine. Side effects typically go away on their own after a few days. The most commonly reported side effects are: 
    • Pain, swelling, and redness at the injection site.
    • Pain, tenderness and swelling of the lymph nodes in the same arm of the injection.
    • Fatigue.
    • Headache.
    • Muscle pain.
    • Chills.
    • Joint pain.
    • Nausea/vomiting.
    • Fever.
  • Different people may experience different side effects, even if they receive the same vaccine. 
  • These symptoms are normal and show that your body’s immune system is responding to a vaccine. Other routine vaccines, like the flu vaccine, have similar side effects.
  • For in-depth information about the side effects of the vaccines, see the CDC’s report on the Pfizer vaccine, the Moderna vaccine, and the Novavax vaccine
When should I seek medical care because of side effects?
  • If you get a COVID-19 vaccine and you think you might be having a severe allergic reaction after leaving the vaccination site, seek immediate medical care by calling 911.
  • In most cases, discomfort from fever or pain after getting the vaccine is normal. Contact your doctor or health care provider:
    • If the redness or tenderness where you got the shot increases after 24 hours.
    • If your side effects are worrying you or do not seem to be going away after a few days.
If I have side effects like fever and chills after getting the vaccine, does that mean I am contagious?
  • Side effects happen one to two days after receiving the vaccine. They can include fever, chills, headache, and fatigue. If you experience the expected side effects within one or two days of receiving a vaccine, it likely means that you are not contagious. 
  • The vaccines do not contain the live virus that causes COVID-19 disease. A COVID-19 vaccine can’t give you COVID-19. 
  • Cough, shortness of breath, nasal congestion, sore throat, or loss of taste or smell are not recognized side effects of the vaccine. These may be signs of COVID-19 infection (or another infection). If you feel any of these symptoms, get tested for COVID-19 as soon as you can.
Will getting vaccinated cause me to test positive for COVID-19?
  • No. Getting vaccinated won’t give you a positive test result. If you test positive shortly after being vaccinated, it means you have a COVID-19 infection unrelated to the vaccine. Stay home until your symptoms improve and you have been fever free (without medication) for 24 hours.
If I don't have side effects after getting a vaccine, is it still working?
  • Yes. Different people will respond differently to the vaccines. While many people will have side effects, some people will not. Even if you do not get side effects, the vaccine is likely working.
Can the vaccine cause an allergic reaction?

Should I get vaccinated if I’ve had an allergic reaction to a vaccine in the past?
  • People with a history of severe allergic reactions to any ingredient of a COVID-19 vaccine should not receive that vaccine. For a full list of ingredients, please see each vaccine’s fact sheet (Moderna, Pfizer, or Novavax). None of the vaccines contain eggs, preservatives, or latex. 
  • Additionally, people who have had an immediate allergic reaction (within seconds or minutes) of any severity to previous doses of a COVID-19 vaccine, its components, or to polysorbate should not receive additional doses of the same vaccine.  
  • People who have had severe allergic reactions to other vaccines or injectable therapies in the past should use caution and talk with their health care provider before deciding whether to get vaccinated. 
  • People with a history of severe allergic reactions which are not related to any vaccine or injectable therapy should get the COVID-19 vaccine. 
What if I am injured by the vaccine? Will I have to pay my own medical bills? 
  • If you or a member of your family get a serious physical injury as a direct result of the COVID-19 vaccine, you can file a claim for medical expenses, lost employment income, and survivor death benefits with the Countermeasure Injury Compensation Program (CICP).
  • You do not need to be a U.S. citizen to file a claim or receive benefits from the Countermeasure Injury Compensation Program (CICP) if you qualify. 
What can I do if I can’t afford to take off work to get the vaccine or recover from side effects? 
  • Under Colorado’s Healthy Families and Workplaces Act (HFWA), you are entitled to paid sick leave from your employer. Among other situations, the law requires employers to provide paid leave for employees who have an illness, injury, or health condition that prevents them from working. Paid sick leave must also be available for getting preventive care such as vaccination. 
  • For more information about HFWA, please visit the Colorado Department of Labor and Employment’s website
Are there any serious side effects of receiving the COVID-19 vaccine?
  • Serious side effects (also known as adverse events) are extremely rare. The federal government takes all reports of vaccine adverse events seriously. 
  • CDC uses many vaccine safety monitoring systems, including the Vaccine Adverse Event Reporting System (VAERS), to watch for adverse events after vaccination. VAERS is useful for quickly detecting unusual or unexpected patterns of adverse event reporting that might signal a possible safety problem with a vaccine. 
  • VAERS accepts reports of any adverse event following vaccination, even if it is not clear that the vaccine caused a serious side effect. 
What serious side effects have been reported for the Johnson & Johnson COVID-19 vaccine?
  • The Johnson & Johnson vaccine is safe and effective in preventing COVID-19, and the benefits greatly outweigh the risks.
  • Serious side effects are extremely rare. There may be increased, but still rare, risks of an abnormal blood clotting disorder called thrombosis with thrombocytopenia syndrome (TTS) in women under age 50 or a nerve disorder called Guillain-Barre syndrome (GBS) in men over age 50.
  • CDPHE has sent information to health care providers to inform them about how to identify and treat TTS and GBS in the very rare case they were to occur. 
  • Health care providers administering the vaccine and vaccine recipients or caregivers should review the Janssen COVID-19 Vaccine Fact Sheet for Healthcare Providers Administering Vaccine (Vaccination Providers) and Fact Sheet for Recipients and Caregivers, which have been revised to include information about the risk of these extremely rare syndromes.
  • People who have received the Janssen vaccine who develop severe headache, abdominal pain, leg pain, or shortness of breath within three weeks after vaccination should contact their health care provider.
Can someone else who received a COVID-19 vaccine shed any of the vaccine components and affect my menstrual cycle?
  • No. Your menstrual cycle cannot be affected by being near someone who received a COVID-19 vaccine. Individuals who have received a COVID-19 vaccine cannot shed any parts of the vaccine. 
  • Many things can affect menstrual cycles, including stress, changes in monthly schedule, problems with sleep, and changes in diet or exercise. Infections may also affect the menstrual cycle.
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Pregnancy, fertility, and COVID-19 vaccines

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Can I get a COVID-19 vaccine if I would like to have a baby one day?
Can I get the vaccine if I am pregnant?

Can I get the vaccine if I am breastfeeding?
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Vaccines for children and teens

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Can children get the vaccine?
How can I make a vaccine appointment for my child?
Is it safe for children to get a COVID-19 vaccine?
How well does the vaccine work for children? 
  • The vaccine works well to prevent serious illness, hospitalization, and death in children.
  • Both Pfizer and Moderna’s vaccines for younger children offered protection from infection in clinical trials, even during the omicron surge. This protection was as good as or better than the vaccines for older children and adults during omicron.
  • Both Pfizer and Moderna’s vaccines for younger children triggered the immune system to make antibodies in clinical trials. This immune response was similar to the response produced by COVID-19 vaccines in young adults. This immune response means it’s very likely the vaccines prevent severe illness, hospitalization, and death in young children.

Do children get the same type of vaccine as adults?
  • It depends on their age. Children age 12 to 17 years get the same kind and dose of vaccines as adults. 
  • Children aged 6 months through 11 years get smaller doses of the vaccines. These doses are tailored to make sure they are safe and effective for each age group.
Do children need to be accompanied by a parent or guardian at their vaccine appointments?
  • The state of Colorado does not require minors to be accompanied as long as parental consent is collected and shared prior to the appointment. This can be done through a paper form or through the vaccine provider’s online scheduling system. The provider may also obtain consent by phone and document it in the patient’s record.
  • Some vaccine providers may require children to have a parent or guardian with them at their appointment. We recommend calling your provider ahead of time to check whether they require parental accompaniment.
What are the side effects of the vaccine for children? 
  • The side effects in children are similar to the side effects experienced by adults. They can include pain, swelling, and redness in the arm where the vaccine was given; tiredness; headache; soreness; chills; and fever. 
  • For children aged 3 years and younger, the most common side effects include pain where the vaccine was given, swollen lymph nodes, irritability or crying, sleepiness, and loss of appetite.
  • Side effects may be more common after the second dose, especially for children aged 4 years and older.
  • In clinical trials, children under 12 years tended to have milder side effects than teens and adults. 
  • Most side effects are mild and go away on their own after a day or two.
Will my child need multiple doses of the vaccine? 
  • It depends on their age, vaccination history, and whether they are immunocompromised.
  • Children aged 6 months through 4 years and immunocompromised children may need multiple doses of the 2023-2024 vaccine to get up to date.
  • Talking with your child’s health care provider can help you learn more about how many doses your child should receive, but it’s not required.
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Health concerns and the vaccine

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Can I get the vaccine if I am immunocompromised?
  • Yes. Immunocompromised people should receive a COVID-19 vaccine if they have no contraindications or reason to believe that getting the vaccine would be harmful to them. Talk with your health care provider if you have additional questions.
  • More information can be found at CDC’s COVID-19 Vaccines for Moderately to Severely Immunocompromised People
  • None of the currently available vaccines contains the virus that causes COVID-19. A COVID-19 vaccine cannot give you COVID-19.
Can I donate blood if I’ve received a COVID-19 vaccine?
  • Yes. According to the American Red Cross and Vitalant, you can donate blood if you’ve received a COVID-19 vaccine manufactured by Pfizer, Modern, Johnson & Johnson, Novavax, or AstraZeneca. You must be symptom-free and fever-free to donate blood. 
  • Check with your local blood center for additional information.

Do younger people get heart symptoms after getting vaccinated?
  • It’s possible, but extremely rare, for people to get conditions called myocarditis and pericarditis after COVID-19 vaccination. 
  • Myocarditis is inflammation of the heart muscle, and pericarditis is inflammation of the outer lining of the heart. In both cases, the body’s immune system causes inflammation in response to an infection or another trigger.
  • Very few people get myocarditis or pericarditis after vaccination, and most cases of these conditions are mild. People often recover on their own or with minimal treatment. 
  • These cases have occurred after vaccination with Pfizer and Moderna, and, more rarely, Novavax, especially in male adolescents and young adults. 
  • Compared to the very low risks of myocarditis and pericarditis after vaccination, people who are infected with COVID-19 are much more likely to develop these conditions. The conditions may be more severe in people who get infected as well. 
  • Scientists have reviewed reports of these conditions and decided that the benefits of the vaccine are greater than the risks. CDPHE and CDC continue to recommend COVID-19 vaccination for everyone aged 6 months and older.
  • For more information about heart symptoms after vaccination, visit CDC’s website.
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How COVID-19 vaccines work

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Can a COVID-19 vaccine make me sick with COVID-19?
  • No. None of the currently authorized vaccines contain the live virus that causes COVID-19 
  • The Novavax vaccine contains small pieces of the COVID-19 virus, but these pieces on their own cannot replicate themselves or make you sick.
What’s the difference between an mRNA vaccine and a protein-based vaccine?
  • Pfizer and Moderna’s vaccines are mRNA vaccines. Novavax’s vaccine is a protein-based vaccine. 
  • All COVID-19 vaccines teach your body how to fight spike proteins like the ones that cover the COVID-19 virus. If you are exposed to COVID-19 after vaccination, your body will recognize the spike proteins and remember how to fight them before the virus makes you sick.
  • mRNA vaccines, like the Pfizer and Moderna vaccines, use single-stranded mRNA to teach your body how to make and fight spike proteins. 
  • The Novavax vaccine contains a very small amount of spike protein taken directly from the COVID-19 virus. It also contains an ingredient called an adjuvant, which boosts the immune system’s response to the protein. The protein and the adjuvant work together to teach your immune system how to recognize and fight COVID-19. The Novavax vaccine does not use any genetic material.
  • The goal of every COVID-19 vaccine is the same. They just use different strategies to achieve that goal.
How do mRNA vaccines work? 
  • The Pfizer and Moderna vaccines are both mRNA vaccines. These vaccines help our bodies build an immune response to the COVID-19 virus. The mRNA vaccines use temporary genetic instructions called mRNA to use your own cells to make a harmless spike protein that is unique to the virus that causes COVID-19. After our cells make copies of the protein, our immune system recognizes that the protein should not be in our body and builds antibodies to remember how to fight the virus if we are infected in the future. 
  • An antibody is a protein produced by your immune system that can recognize a specific type of virus in your body. When you get exposed to the actual COVID-19 virus, your body’s antibodies are able to recognize proteins on the surface of the virus to attack and stop it from replicating in your body.
  • For a visual explanation of how mRNA vaccines work, watch Stat’s video “What are mRNA vaccines?
  • To learn more, visit CDC’s Understanding How COVID-19 Vaccines Work
How do protein-based vaccines work?
  • The Novavax vaccine is a protein-based vaccine. It contains a very small amount of spike protein taken directly from the COVID-19 virus. It also contains an ingredient called an adjuvant, which boosts the immune system’s response to the protein. The protein and the adjuvant work together to teach your immune system how to recognize and fight COVID-19.
  • FDA-approved protein-based vaccines have been used widely for decades to prevent other diseases. The hepatitis B and shingles vaccines are both protein-based.

Can COVID-19 vaccines change my genes? 
  • No. None of the COVID-19 vaccines can change your body’s genes, which are made of DNA (deoxyribonucleic acid).
  • While mRNA (messenger ribonucleic acid) COVID-19 vaccines use temporary genetic code to teach your body how to fight COVID-19, that genetic code does not stay in your body after your immune system has learned how to protect you from the virus.
Do any of the vaccines contain harmful ingredients?
  • Today’s vaccines use only the ingredients they need to be as safe and effective as possible. Each ingredient in a vaccine serves a specific purpose: provide immunity (protection) and keep the vaccine safe and long-lasting.
  • All vaccines contain antigens or elements that trigger the production of antigens. Antigens make vaccines work. They help the body create the immune response needed to protect against infection. Antigens come in several forms. The form used in a vaccine is chosen because studies show it is the best way to protect against a particular infection. 
  • Other ingredients in vaccines may include preservatives, to keep germs out; adjuvants, to help boost the immune response to the vaccine; and additives, which help the vaccine stay effective while being stored. Each ingredient has a specific function and has been rigorously studied. These ingredients are safe for humans in the amounts used in vaccines.
  • For a full list of ingredients, please see each vaccine’s fact sheet (Moderna, Pfizer, or Novavax). 
Do any of the vaccines contain human cells or tissue?
  • None of the currently authorized vaccines contain human cells or tissue. However, Pfizer and Moderna used human cell lines to test their vaccines.
    • Human cell lines are sometimes used in the early stages of vaccine development because viruses from which those vaccines are made need living cells to reproduce. These cell lines originally came from fetal tissue more than 30 years ago. None of the original tissue remains today: all descended cells are grown in labs. No new fetal tissue is required in the ongoing development and production of vaccines.
    • Multiple purification steps ensure that cells are not in the final vaccine product.
    • For more information about human cell lines, please see the College of Physicians of Philadelphia’s webpage Human Cell Strains in Vaccine Development.
  • No human cell lines were used in the development, manufacture, or production of Novavax.
  • For a full list of ingredients, please see each vaccine’s fact sheet (Moderna, Pfizer, or Novavax). 
  • If you have ethical concerns about the vaccines, we encourage you to talk to your faith leaders about them.
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Vaccine safety

For additional information, visit CDC’s Ensuring COVID-19 Vaccine Safety in the US webpage.

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How do we know that the vaccines are safe?
  • COVID-19 vaccines have gone through the most intense safety monitoring in U.S. history. 
  • Hundreds of millions of people in the U.S. have safely received a COVID-19 vaccine.
  • The FDA requires vaccines to go through a rigorous scientific process before they become available to the public. The COVID-19 vaccines are held to the same safety standards as other vaccines. 
  • Read more about how we know COVID-19 vaccines are safe.
How were the original COVID-19 vaccines developed so quickly? 
  • Because COVID-19 was a global emergency, medical researchers around the world worked as hard as they could to create vaccines that would save people’s lives.
  • In developing a vaccine for COVID-19, researchers had to work quickly, but not at the risk of anyone’s safety. Researchers did not cut any corners or skip any steps. Safety and effectiveness were the top priorities. 
  • The timeline for developing COVID-19 vaccines was possible for several reasons: 
    • Researchers relied on years of previous research in other viruses and vaccines to help develop COVID-19 vaccines. COVID-19 is similar in some ways to other viruses, so scientists already had some information about how the virus behaves and how to fight it. They didn’t have to start from scratch.
    • Everyone involved dedicated all their resources and time to developing a COVID-19 vaccine. This includes research institutions, government agencies, philanthropic organizations, and pharmaceutical companies. 
    • Many governments around the world, including the U.S. government, and private funders invested in the vaccine. This allowed pharmaceutical companies to focus on research right away. 
    • Because of the emergency presented by the pandemic, researchers developed the vaccines on parallel tracks, meaning that they completed the necessary steps at the same time or with some overlap. No steps were skipped in the process of developing the COVID-19 vaccines. 
    • Because so many people were exposed to COVID-19 during the pandemic, vaccine testing could be completed much faster than for diseases that are less common.
Did the 2023-2024 vaccines go through the same authorization process as the original COVID-19 vaccines?
  • The updated vaccines use the same technology as the mRNA vaccines that hundreds of millions of people have safely received. Researchers used their existing knowledge of mRNA vaccines to make slight adjustments that would improve the vaccines’ effectiveness against the current COVID-19 variants.
  • Because the 2023-2024 vaccines are slightly altered versions of previously approved vaccines, they did not have to go through the same clinical trials as the original formulations before becoming available to the public. 
  • This process is very similar to the process that the flu vaccine goes through every year to make sure it targets the most current version of the flu virus. Like flu vaccines, the updated COVID-19 vaccines are safe and work to protect you from the variants of the virus currently circulating in the United States.
Is it safe for children to get the COVID-19 vaccine?
 
 

Who approves vaccines in the United States? 
  • The Food and Drug Administration (FDA) licenses and approves the use of vaccines. Before the FDA approves a vaccine, the manufacturer must do rigorous research and testing to ensure the vaccine’s safety and effectiveness. The FDA independently reviews and verifies the information from these tests. It then decides whether the vaccine can be authorized and given to the public. 
  • In certain emergency situations, the FDA may issue an Emergency Use Authorization (EUA) to provide more timely access to critical medical products when there are no other options available. 
How are the vaccines tested? 
How is vaccine safety monitored once the vaccine is approved or authorized? 
  • The FDA and CDC closely monitor vaccine safety after the public begins using the vaccine. Both agencies have systems in place to keep an eye on the safety of COVID-19 vaccines. Learn more about the different vaccine safety monitoring systems: 
    • Vaccine Adverse Event Reporting System (VAERS) collects and analyzes reports of any problems that happen after vaccination. Anyone can submit a report, including parents, patients, and health care professionals.
    • Vaccine Safety Datalink (VSD) is a collaboration between CDC and several health care organizations to monitor vaccine safety. The system analyzes healthcare information for over 24 million people to conduct studies about rare and serious adverse events after immunization. 
    • Post-licensure Rapid Immunization Safety Monitoring (PRISM) is the FDA’s immunization safety monitoring program. PRISM actively monitors the safety of medical products using electronic health information from over 190 million people. 
    • Clinical Immunization Safety Assessment Project (CISA) is a collaboration between CDC and seven medical research centers to answer complex safety questions. CISA conducts clinical research studies to further understand vaccine safety and recommend prevention strategies for adverse events following immunization.
  • Vaccine recommendations may change if safety monitoring reveals new information about vaccine risks, such as a new serious side effect. The CDC, with the help of the Colorado Department of Public Health and Environment, will send safety alerts to health care providers. If necessary, the federal government may remove a vaccine from the market.
Can the vaccines cause death? 
  • None of the COVID-19 vaccines currently available in the U.S. has been linked with an increased risk of death. FDA and CDC do not approve vaccines of any kind that have more risks than benefits.
  • CDC uses the Vaccine Adverse Event Reporting System (VAERS) to closely monitor reports of death following COVID-19 vaccination.
  • Reports of death after vaccination do not necessarily mean the vaccine caused the death. There are deaths every day from a variety of causes.
  • CDC follows up on any report of death to ask for more information. They use this information to learn more about what happened and to find out whether the death had something to do with the vaccine.Find out more on CDC’s Selected Adverse Events Reported after COVID-19 Vaccination
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COVID-19 immunity and protecting others after getting the vaccine

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When will I be protected after I get the vaccine?
  • It takes up to two weeks after you’ve received your last recommended dose for your body to fully protect itself.
Is natural immunity from having COVID-19 better than getting a vaccine?
  • In order to get natural immunity, you have to become infected with COVID-19, which can come with many serious risks and complications. Getting the vaccine gives you protection without the risks of illness.
  • Getting a COVID-19 vaccine after having a COVID-19 infection provides added protection. People who already had COVID-19 and do not get vaccinated after their recovery are more likely to get COVID-19 again than those who get vaccinated after their recovery.
If I get vaccinated, is it possible for me to still get COVID-19?

Yes. Some people who are vaccinated against COVID-19 still get sick. However, the risk of getting severely sick, dying, or developing Long COVID is lower if you are up to date on your vaccines.

Why should I get vaccinated if I might get sick anyway?
  • If you do get sick after being vaccinated, it is much less likely that your symptoms will be severe or that you will need to be hospitalized. Staying up to date with vaccines also greatly reduces the risk of death from COVID-19.
Do I need to isolate if I develop COVID-19-like symptoms after I have been vaccinated?
  • If you develop COVID-19 symptoms at any time, stay home until you feel better and have been fever free (without medication) for 24 hours. People most at risk for severe illness, including those older than 65 years and people with weakened immune systems, may want to consider more precautions.
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Emergency Use Authorization

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What is an Emergency Use Authorization? 
  • In certain emergency situations, the Food and Drug Administration (FDA) may issue an Emergency Use Authorization to provide more timely access to critical medicines when there are no other options available. An Emergency Use Authorization permits the FDA to allow medical products that have met certain criteria, to treat, diagnose, or prevent serious or life-threatening diseases to be used.
  • Watch this short video from the FDA about Emergency Use Authorization.