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COVID-19 vaccine FAQ

Back to vaccines

Last updated Oct. 24, 2025

Available languages: Español

 

 

Top 10 most frequently asked questions

#1 Where can I get a COVID-19 vaccine? 
  • COVID-19 vaccines are available at  many doctor’s offices, local public health agencies, community health centers, and pharmacies.
  • Ask your regular health care provider or pharmacy if they have COVID-19 vaccines.
#2 How do we know that the vaccines are safe?
  • COVID-19 vaccines went through the most intense safety monitoring in U.S. history.
  • The 2025-2026 COVID-19 vaccines use the same proven, Nobel prize-winning technology as the vaccines that hundreds of millions of people have safely received. Like the seasonal flu vaccine, the COVID-19 vaccine gets updated to protect against newer 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.
  • Over the past five years, hundreds of millions of people in the United States received COVID-19 vaccines under the most intense safety monitoring in U.S. history.
  • Learn more about vaccine safety.
#3 Do I need more than one dose of a 2025-2026 COVID-19 vaccine?
  • Most people need only one dose of an updated 2025-2026 COVID-19 vaccine. However, the COVID-19 vaccine formulation and number of doses recommended for you are based on your age and vaccination history. Talk to your health care provider or pharmacist about the number of doses recommended for you.
#4 Can I get a COVID-19 vaccine at the same time as my annual flu vaccine?
  • Yes. It’s safe to get COVID-19 and flu vaccines at the same appointment.
  • If you or your child are due for other childhood or adult vaccines, ask your provider about adding them to your appointment as well.
#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 and vaccination during pregnancy builds antibodies that can help protect your baby.
  • 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 those who are pregnant and those 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?
  • Most insurance providers cover COVID-19 vaccines at no cost to you.
  • If your health insurance plan does not cover COVID-19 vaccines completely with no out of pocket costs, you are considered underinsured.
  • Uninsured and underinsured people qualify for federal vaccine programs. The Vaccines for Children program provides no and low-cost COVID-19 vaccines for children who are uninsured, underinsured, on Medicaid or Medicaid eligible, and/or Alaskan Native/American Indian. Some Vaccines for Children providers may also have low- and no-cost vaccines for uninsured and underinsured adults aged 19 years and older.
    • While these providers may ask you for the following, you are not required to provide them in order to receive a publicly funded vaccine:

#7 Do I need to be a U.S. citizen to get a vaccine? 
#8 How were the vaccines developed so quickly? 
  • The FDA worked closely with the vaccine manufacturers to ensure the development of these newly updated COVID-19 vaccines was done safely and efficiently.
  • The 2025-2026 vaccines run on the same trusted technology as the earlier formulations of COVID-19 vaccines.
  • Similar to the yearly flu vaccine, COVID-19 vaccines are updated to target the newer 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 and protein-based 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 How do if I find my vaccine record?

  • Use the table below for tips on how to find your immunization record.

    Where vaccines were received

    Where to find the vaccine record

    If vaccines were received in Colorado

    Request your/your child’s immunization record from the Colorado Immunization Information System (CIIS) public portal. CIIS is the quickest and easiest way to access vaccine records.

    If vaccines were received in a state other than Colorado 

    Some states have a public immunization record request portal similar to Colorado. Contact the Immunization Information System in the city, state, or territory where you/your child received their last vaccines. Colorado has an interjurisdictional data exchange set up with Kansas, Nevada, New Mexico, Oklahoma, and Pennsylvania. Information from those states may be available in CIIS.

    If vaccines are not documented in a state’s immunization information system

    Contact your/your child’s health care provider or clinic.

     

    Use CDC’s Keep Track of Records webpage for more resources. 

    If vaccines were received outside of the United States or your health care provider does not have an immunization record for you/your child

    Use this tip sheet for locating old immunization records or make an appointment with your/your child’s primary care provider.

Getting a COVID-19 vaccine

What types of COVID-19 vaccines are available? 
  • Vaccines made by Pfizer, Moderna, and Novavax are currently available in the United States. All COVID-19 vaccines have been updated for the 2025-2026 respiratory season.
  • None of the updated 2025-2026 COVID-19 vaccines is preferred over another.
  • CDC has detailed information about each vaccine on its COVID-19 Vaccine Basics page.  
How many doses of the COVID-19 vaccine do I need?
How do I know what kind of vaccine I’ve received in the past?
  • The vaccine card you received at your very first COVID-19 vaccine appointment should list the COVID-19 vaccines you’ve received. If you no longer have your vaccine card, or your vaccine card is incomplete, you can find your immunization record in the Colorado Immunization Information System Public Portal. If you have difficulty finding your record, review this guidance document. Email cdphe.ciis@state.co.us for additional assistance.
  • If you got your COVID-19 vaccination(s) outside of Colorado, or your vaccine is not recorded in the Colorado Immunization Information System, 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.
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 2025-2026 COVID-19 vaccine (Novavax’s Nuvaxovid, Pfizer’s Comirnaty, Moderna’s Spikevax, or Moderna’s Mnexspike). It doesn’t matter what kind of vaccines you received in the past.
  • Children aged 5 through 11 years can get either Pfizer's Comirnaty or Moderna’s Spikevax 2025-2026 COVID-19 vaccine. It doesn’t matter what kind of vaccines you received in the past.
  • Moderna’s Spikevax is the only COVID-19 vaccine available for children aged 6 months through 4 years.
  • Children aged 6 months through 4 years and people of any age who are moderately or severely immunocompromised should receive the same brand of vaccine for all their doses when possible. Talking with your/your child’s health care provider can help you learn more about which vaccine they should get, but it’s not required.
Why should I get 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.
  • All viruses mutate over time, including COVID-19. Similar to the yearly flu vaccine, COVID-19 vaccines are updated to target the newer strains of COVID-19 that are circulating in the United States.
  • Getting an updated 2025-2026 vaccine gives targeted protection from the newer COVID-19 variants circulating right now. The 2025-2026 vaccines are designed to help the immune system better fight these current variants compared to previous COVID-19 vaccines.
Should I get vaccinated if I’ve already had COVID-19?
  • Yes. COVID-19 vaccination is recommended even if you’ve already had COVID-19.
  • It is safe to get a vaccine as soon as you feel better, and as long as it’s been at least two months since your most recent dose of an earlier COVID-19 vaccine (or three months if you get Moderna's mNexspike 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.
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 be given at the same time, if needed, or close together.
  • Your health care provider 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 health care provider about additional concerns you might have about getting more than one vaccine at the same time. 
Can I get the vaccine at my health care provider’s office or local pharmacy? 
  • Many pharmacies, health care provider’s offices, community health centers, and other locations offer COVID-19 vaccines. Contact your health care provider for more information.
  • Hundreds of provider offices, community health centers and local public health agencies have free or low-cost COVID-19 vaccines for children eligible for the federal Vaccines for Children (VFC) program. Use CDPHE’s VFC provider map to locate an immunization provider near you.
  • Retail pharmacies no longer have free or low-cost doses of COVID-19 vaccines for uninsured or underinsured adults. If you are uninsured or underinsured, use CDPHE’s Find a COVID-19 vaccine webpage to locate an immunizing provider near you.
  • Call 1-800-232-0233 to find vaccine appointments near you.
  • Visit vaccinefinder.org to find a pharmacy near you.
I need a ride to my vaccine appointment. What are my options?

Through a partnership with Lyft, Mile High United Way’s 211 program connects qualifying individuals and families with rides to get to medical appointments. Dial 2-1-1 to learn more and to find out if you are eligible.

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 program, like the Vaccines for Children program, to get an updated COVID-19 vaccine at low or no cost.
  • 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 when receiving other vaccines and health services, 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, 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.
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, like through the Vaccines for Children program. Underinsured and uninsured people 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, there is no need to get a test before your vaccine appointment.

Vaccine side effects

What are possible side effects of the vaccines? 
  • You may experience mild to moderate side effects after receiving the COVID-19 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 show that your body’s immune system is responding to a vaccine. Other routine vaccines, like the flu vaccine, may have similar side effects.
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 working.
Can the vaccine cause an allergic reaction?
  • Although it is rare, the COVID-19 vaccines may cause mild allergic reactions in some people, like itching or rash. In extremely rare cases, some people may have a severe allergic reaction (e.g. anaphylaxis). If this occurs, vaccination providers will immediately treat the reaction.
  • 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.
  • If you had a reaction following a vaccination, contact your health care provider. You can also submit a report to the Vaccine Adverse Event Reporting System (VAERS).
  • For more information, see CDC's What to Do If You Have an Allergic Reaction after Getting a COVID-19 Vaccine.

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 package insert (Moderna's Spikevax, Moderna's mNexspike, Pfizer's Comirnaty, or Novavax's Nuvaxovid). 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. 
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.
  • More information is available on the CDC Vaccine Safety Systems webpage.
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.
  • People who menstruate who do get a COVID-19 vaccine may not observe any changes or they may observe small and temporary changes in their periods including:
    • Longer-lasting menstrual periods.
    • Shorter intervals between periods.
    • Heavier bleeding than usual.

Pregnancy, fertility, and COVID-19 vaccines

Can I get a COVID-19 vaccine if I would like to have a baby one day?
  • Yes. If you or your partner are trying to become pregnant now or want to have a child in the future, you should get a COVID-19 vaccine.
    There is currently no evidence that any vaccines, including COVID-19 vaccines, cause fertility problems in women or men. 
    Many people have become pregnant after receiving a COVID-19 vaccine, including some who got vaccinated during COVID-19 vaccine clinical trials.
    Studies have found no differences in pregnancy success rates among women who had antibodies from COVID-19 vaccines or from recent COVID-19 infection and women who had no antibodies.
    Studies have also found no significant changes in sperm characteristics, like quantity and movement, after vaccination.
  • Please talk with your doctor for more information if you have any concerns.
    For more information, visit the CDC’s COVID-19 Vaccines for People Who Would Like to Have a Baby webpage. 
Can I get the vaccine if I am pregnant?
  • Yes. The best way to protect yourself and your baby from COVID-19 is to get vaccinated. COVID-19 can make you very sick during pregnancy. Additionally, if you have COVID-19 during pregnancy, you are at increased risk of complications that can affect your pregnancy and developing baby.
  • There is now more evidence than ever to show that COVID-19 vaccines are safe for those who are pregnant.
  • Additional actions you can take to protect yourself include wearing a mask in public, keeping your distance from people who don’t live with you, washing your hands frequently, and limiting gatherings. These precautions are especially important if you live in an area where COVID-19 is spreading widely.

Can I get the vaccine if I am breastfeeding?

Vaccines for children and teens

Can children get the vaccine?
  • Yes, children as young as 6 months old can get a COVID-19 vaccine.
  • FDA approved Moderna’s Spikevax COVID-19 vaccine for people aged 6 months and older. Pfizer's Comirnaty is approved for people 5 years and older. The Novavax vaccine (Nuvaxovid) and Moderna's mNexspike are approved for people aged 12 years and older. 
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. Data shows that the COVID-19 vaccine protects children against serious COVID-19 outcomes.

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. Call 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 with other vaccines. They can include pain, swelling, and redness in the arm where the vaccine was given, tiredness, headache, soreness, chills, and fever.
  • 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? 
  • The number of recommended COVID-19 vaccine doses depends on their age, vaccination history, and whether they are immunocompromised.
  • 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.

Health concerns and the vaccine

Can I get the vaccine if I am immunocompromised?
  • Yes. Immunocompromised people should receive a COVID-19 vaccine. Talk to your health care provider if you have additional questions.
    • In addition to vaccination, a preventive monoclonal antibody called Pemgarda may provide another layer of protection for immunocompromised people aged 12 years and older. Pemgarda can be given at least two weeks after receiving a COVID-19 vaccine. Talk with your health care provider for more information.
  • More information can be found at CDC’s COVID-19 Vaccines for Moderately to Severely Immunocompromised People and the Infectious Disease Society of America's Guidelines on COVID-19 vaccination.
  • 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, you can donate blood if you’ve received a COVID-19 vaccine. 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?
  • While it’s possible for people to get conditions called myocarditis and pericarditis after COVID-19 vaccination, myocarditis is more common after COVID-19 infection. Myocarditis is inflammation of the heart muscle, and pericarditis is inflammation of the outer lining of the heart.
  • Myocarditis and pericarditis have occurred more often after vaccination with mRNA COVID-19 vaccines, and more often in male adolescents and young adults.
  • 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 COVID-19 Vaccine Safety webpage.

How COVID-19 vaccines work

Can a COVID-19 vaccine make me sick with COVID-19?
  • No. None of the currently licensed 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?
  • All COVID-19 vaccines teach your body how to recognize spike proteins like the ones that cover the COVID-19 virus. If you are exposed to COVID-19 after vaccination, your body will see the spike proteins and remember how to fight the virus before it makes you very sick.
  • Pfizer and Moderna's vaccines are mRNA vaccines that use mRNA genetic instructions to teach your body how to recognize spike proteins in the future and fight the COVID-19 virus.
  • Novavax's vaccine is a protein-based vaccine that uses pre-made spike proteins to teach your body to recognize spike proteins in the future and fight the COVID-19 virus. It also contains an ingredient called an adjuvant to boost the immune system’s response to the spike protein. There is no genetic material in the Novavax vaccine.
  • 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 your body build an immune response to the COVID-19 virus. The mRNA vaccines use temporary genetic instructions called mRNA that your own cells use to make harmless spike protein that is unique to the virus that causes COVID-19. After your cells make copies of the spike protein, your immune system recognizes that the protein should not be in our body and builds antibodies to remember how to fight the virus 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 COVID-19 Vaccine Basics.
How do protein-based vaccines work?
  • The Novavax vaccine is a protein-based vaccine, which means it contains a very small amount of pre-made spike protein. 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 with adjuvant have been used widely for decades to prevent other diseases. The hepatitis B and shingles vaccines are both protein-based and contain an adjuvant.

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. Your body already knows how to get rid of mRNA after it has been used.
Do any of the vaccines contain harmful ingredients?
  • Today’s vaccines use only the ingredients they need to give the best protection 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 package insert (Moderna's Spikevax, Moderna's mNexspike, Pfizer's Comirnaty, or Novavax's Nuvaxovid). 
Do any of the vaccines contain human cells or tissue?
  • None of the currently approved 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 the Novavax vaccine.
  • For a full list of ingredients, please see each vaccine’s package insert (Moderna's Spikevax, Moderna's mNexspike, Pfizer's Comirnaty, or Novavax's Nuvaxovid).  
  • If you have ethical concerns about the vaccines, we encourage you to talk to your faith leaders about them.

Vaccine safety

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 2025-2026 vaccines go through the same regulatory 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 use their existing knowledge of mRNA vaccines to make slight adjustments to improve the vaccines’ effectiveness against the current COVID-19 variants.
  • Because the 2025-2026 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? 
  • 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 eight 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 COVID-19 Vaccine Safety webpage.

COVID-19 immunity and protecting others after getting the vaccine

When will I be protected after I get the vaccine?
  • It can take up to two weeks after you’ve received a vaccine 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. People who are vaccinated against COVID-19 can 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. 
  • If you test positive for COVID-19, you may be able to get medicine to help you recover. Talk to your doctor to see if treatment is right for you.