COVID-19 Vaccines
It's completely normal to have questions about COVID-19 vaccines. While medical and public health experts are still learning about COVID-19, there is a lot we do know about the vaccines that prevent it. Find answers to your questions in the Children's Hospital Colorado video series and list of frequently asked questions (FAQ) below.
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COVID-19 Vaccine FAQs (Frequently Asked Questions)
How Do COVID-19 Vaccines Work?
The current COVID-19 vaccines used in the United States are Pfizer, Moderna, Johnson & Johnson, and Novavax. The Moderna and Pfizer vaccines are mRNA vaccines and require two doses. The J&J vaccine is an adenovirus viral vector vaccine and requires only one dose. The Novavax vaccine is a protein subunit vaccine and requires two doses.
On May 5, 2022, the FDA limited the use of the J&J vaccine to individuals 18 and up for whom other vaccines are not accessible or appropriate and to those who would otherwise not receive a COVID-19 vaccination. This action was taken due to the risk of thrombosis with thrombocytopenia syndrome, or TTS. Though this side effect is very rare, TTS can cause blood clots which can be dangerous.
mRNA vaccines provide a set of instructions that teach our cells how to make a piece of a spike protein that triggers an immune response in our bodies. This causes our bodies to begin making protective antibodies, just like it would if we encountered COVID-19 virus. These antibodies are then prepped and ready to fight off the virus if we are ever exposed to it, before it causes infection. mRNA vaccines cannot make you sick with COVID-19 because they do not use the live virus that causes COVID-19. mRNA vaccines do not change or alter your DNA. Once the vaccine is done triggering our cells to create the spike protein, our cells break down the mRNA and expel it. Watch this video to learn more.
Viral vector vaccines work by using a different virus (in the J&J/Janssen COVID-19 vaccine, this virus is called an "adenovirus") as a vector to deliver important instructions in the form of a gene to our cells. In the COVID-19 vaccine, this gene instructs our cells to make the SARS-CoV-2 spike protein, which triggers production of antibodies and results in a strong immune response. The vaccine cannot cause infection with either COVID-19 or the virus vector (adenovirus). Viral vector vaccines have been well-studied and have even been used to respond to recent Ebola outbreaks. Watch this video to learn more.
The Novavax protein subunit vaccine teaches the body to fight the coronavirus by delivering copies of the virus’ spike protein (the spikes on the outer sphere of the virus) to the body. The immune system recognizes these proteins as dangerous and creates antibodies, which provide protection against future COVID infection. The proteins are grown in insect cells and purified. Like other vaccines, the Novavax vaccine cannot cause COVID infection. The Novavax vaccine was developed in a way that is similar to other widely used vaccines, such as the Human Papillomavirus vaccine and the Hepatitis B vaccine.
The number of doses varies based on the type of vaccine administered, a person’s age, and their immunocompromised status. The CDC’s COVID-19 Vaccination Schedule provides a useful visual representation of the dosing schedule. For best protection, individuals should stay up to date with both an initial vaccine series and booster doses. Use the CDC's Booster Calculator to determine if and when you should receive a booster based on your age and immunocompromised status.
People who get the COVID-19 vaccine may experience no side effects at all. Others may experience mild side effects, which may include pain, swelling or redness at the injection site, fatigue, low-grade fever, chills, or headache. These side effects are common and a sign that the vaccine is doing its job and your body is mounting a robust immune response against future infections. Experiencing these side effects does not mean you have COVID-19. Remember, the vaccine cannot give you COVID-19. If you are able, do not take pain or cold medication as this might affect your body's future immune response to a COVID-19 infection.
Additionally, the COVID-19 vaccine has been shown to be safe for the pediatric population 6 months of age and over. There were no serious safety concerns found for this age group in clinical trials. COVID-19 vaccines are also safe to give along with other essential routine vaccinations. It is also important to note that there is more data on COVID-19 vaccine safety than there is for most medications, supplements, and vitamins.
On May 5, 2022, the FDA limited the use of the J&J vaccine to individuals 18 and up for whom other vaccines are not accessible or appropriate and to those who would otherwise not receive a COVID-19 vaccination. This action was taken due to the risk of thrombosis with thrombocytopenia syndrome, or TTS. It can cause blood clots which can be dangerous. The Pfizer, Moderna, and Novavax vaccines are preferred over the use of the J&J vaccine due to the very rare occurrence of TTS. Additionally, Moderna, Pfizer, and Novavax offer increased protection from COVID-19 over J&J. Those who got the J&J vaccine initially should receive a booster dose of Pfizer or Moderna vaccine; Novavax is not currently authorized as a booster.
No. Viral shedding occurs when small, whole viral particles are secreted from an infected person. In the case of the COVID-19 virus, this shedding might occur in saliva or mucus. With the COVID-19 vaccines, there is no live infection. Only a part of the virus–the spike protein–is produced in mRNA, adenovirus, and protein subunit vaccines, not a whole viral particle (and that viral part does not replicate in the body). It is impossible for any viral shedding to occur as a result of the vaccine.
Who Can Get a COVID-19 Vaccine?
COVID-19 vaccines are one of the best tools we have to fight the COVID-19 pandemic and help restore health and economic security for our families and communities. Getting the COVID-19 vaccine will help protect yourself, your family and your community from COVID-19. Together, we can help end the pandemic; it's up to all of us.
Everyone ages 6 months and older who wants a vaccine can and should receive one. Read on below for specific guidance for pregnant persons, immune-compromised people, people with allergies, and young children.
Yes. Some studies have shown that after getting vaccinated against COVID-19, the body's immune response protecting us against the virus may not be as strong over time, decreasing its ability to protect against infection. This lowered effectiveness is likely also due to the greater infectiousness of the Delta and Omicron variants. Because of this the CDC recommends everyone eligible stay up to date with the COVID-19 vaccine series and boosters. Boosters are currently available from Pfizer, Moderna, and Novavax. Use the CDC’s “Find Out When You Can Get Your Booster” tool to see when you’re eligible for a booster. Find a COVID-19 vaccine provider here.
New boosters are now available following CDC recommendation:
Bivalent boosters are available for individuals six months of age and older. These bivalent boosters from Pfizer and Moderna provide increased protection against Omicron variants as well as the original coronavirus strain. The monovalent booster from Novavax provides a booster option for people who cannot or will not get mRNA vaccines. Individuals can get either the Pfizer or Moderna booster regardless of whether their previous dose was Pfizer, Moderna, Novavax, or Johnson & Johnson. If you recently had a COVID-19 infection, you may wait 3 months from the onset of symptoms or positive test to get a booster. This link from the Colorado Department of Public Health and Environment (CDPHE) can help you find a vaccination clinic providing boosters.
Adults and children who are immunocompromised are at greater risk for severe illness and death from COVID-19 infection. This group of individuals has different recommendations for COVID-19 vaccines, including an additional dose. An additional dose is not the same as a booster dose. An additional dose is considered part of the initial vaccine series, whereas a booster is not. The CDC provides detailed information on additional and booster doses for immunocompromised individuals based on age, brand of vaccine, and length of time since last dose. Regardless of immunocompromised status, everyone should ensure they are up to date with COVID-19 doses and boosters.
While the CDC did announce that anyone who is eligible for a booster could get a different booster than their primary dose, mix and match is not required. However, those who received a primary dose of J&J vaccine should receive a Pfizer or Moderna booster, or a Novavax booster if they cannot or will not reveive mRNA vaccines. There is some early data that there is an elevated immune response to a different mRNA vaccine, but results are not conclusive and more data is needed.
You can get both the flu vaccine and a COVID-19 vaccine at the same time. Experts recommend that the vaccines be given in two separate locations–either one inch apart in the same arm or one in each arm.
Yes. People who have previously had COVID-19 infection can and should be vaccinated. Those currently infected should wait until their illness has resolved to get the vaccine. Because reinfection with the coronavirus is uncommon in the 90 days following initial infection, people who have had recent infection can still get vaccinated. They may choose to delay vaccination until the end of that 90-day period but are not required to do so. It is unclear how long natural immunity from COVID-19 disease lasts, or if it will protect from new variants. Getting vaccinated if you've already had COVID-19 adds an extra layer of protection against reinfection and severe illness.
People with severe allergies to a COVID-19 vaccine ingredient, a previous dose of COVID-19 vaccine, or to polysorbate should not get the COVID-19 vaccines. People who have had a severe allergic reaction to other vaccines in the past should consult their health care provider or an immunologist before receiving the vaccine. People with severe allergies to anything else (medications, foods, bees, etc.) are allowed to get the COVID-19 vaccine but should wait at the location the vaccine was given for 30 minutes, instead of the 15 minutes that the general population is recommended to wait. The Novavax protein subunit vaccine is now another option for people who are allergic to one of the components of the viral vector or mRNA vaccines.
The CDC has published information that shows over 2 million doses of the Pfizer COVID-19 vaccine, only 21 individuals had an allergic reaction. Most of those reactions occurred in the initial 15 minutes after the vaccine was administered.
Yes. People who are pregnant or breastfeeding are strongly recommended to get vaccinated for COVID-19. According to the CDC, pregnant people who become infected with COVID-19 are 15 times more likely to die and 22 times more likely to have pre-term births than pregnant people not infected. COVID-19 vaccines are safe for pregnant people and can drastically reduce the risk of adverse pregnancy and neonatal outcomes. Pregnant and breastfeeding persons can consult with their health care provider before being vaccinated but aren’t required to. People who are trying to get pregnant do not need to avoid pregnancy after getting a COVID-19 vaccine.
Yes. Children 6 months and over can now receive the Pfizer or Moderna COVID-19 vaccines.
COVID-19 vaccines are approved for use in people as young as 6 months old, and are recommended by the FDA, CDC, and the American Association of Pediatrics to prevent COVID-19 and the severe condition Multi-Inflammatory Syndrome in Children (MIS-C). Even if a child has had COVID-19, it is unclear how long natural immunity will last, and vaccination is the strongest precaution against reinfection, severe illness and death. We cannot predict the severity of infection in children, and it is not safe to say that children don’t experience severe illness with COVID-19 infection - in fact, 50% of children that have been hospitalized from COVID-19 had no underlying conditions!
The pandemic has hit Black, Latinx, Native American and immigrant communities particularly hard due to systemic inequities fueled by historic racism. The vaccine will be critical for mitigating COVID-19’s continued impact on these communities. In Colorado, the Colorado Vaccine Equity Taskforce was formed to ensure that all groups – regardless of race, ethnicity, ability and other factors – have all the facts to make informed decisions about the safety of vaccines for their families, and to hold leaders accountable for ensuring access to these vaccines for all.
How Can I Get Vaccinated?
Anyone 6 months of age and older can receive a COVID-19 vaccine at numerous locations across Colorado. For information about where to get vaccinated in your area, visit the Colorado Department of Public Health and Environment’s website or call the vaccine hotline at 1-877-COVAXCO (1-877-268-2926). The hotline is available 24 hours a day, 7 days a week with answers available in multiple languages. Some vaccination sites and clinics require appointments, while others are available for walk-ups.
Don’t let transportation challenges stop you (or your family or friends) from getting vaccinated. Mile High United Way is providing access to free rides to vaccination sites across Colorado, Monday - Friday, 8am - 5pm, through their Ride United Program. Dial 2-1-1 or visit 211colorado.org/covid-19 to learn more.
Some people will be required to get a COVID-19 vaccine. This depends on a variety of factors, like where you work and/or where you go to school.
- Work Requirements
While many employers have lifted COVID-19 vaccine mandates, some continue to require COVID-19 vaccination as a condition of employment. The Occupational Safety and Health Administration (OSHA) strongly encourages vaccination.
- School Requirements
There is currently not a vaccine requirement in place for COVID-19 vaccines for Colorado K-12 schools and students. However, some colleges and universities have implemented COVID-19 vaccine requirements for students, staff, and faculty. Please check with your college or university to understand their specific requirements.
Yes, the vaccine is free. No, you will not be required to show identification. No one, whether they are privately insured, on Medicaid or Medicare, or uninsured will have to pay to get the COVID-19 vaccine. You will not be asked to provide proof of insurance for the COVID-19 vaccine. Everyone, regardless of documentation status, can receive a vaccine. In Colorado, a vaccine provider should not ask to see your ID. You may need to provide basic information like name and phone number before getting your vaccine for contact purposes.
Your information won’t be used for anything other than vaccine distribution and follow-up information about 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. You do not need to be a U.S. citizen to get a COVID-19 vaccine, and you will not need to provide a government-issued ID to get the vaccine in Colorado. Your immunization records are confidential, personal medical information, and public health will never share them publicly. You do not need to provide proof of insurance to receive the vaccine.
Yes. In Colorado, the Healthy Families and Workplaces Act concerning paid leave rights allows employees to use supplemental public health emergency (PHE) leave to seek preventative care, including getting vaccinated, during a public health emergency.
Are the Vaccines Safe?
Yes. No corners were cut in developing safe vaccines, despite the speed at which they were developed. Scientists have been researching coronavirus vaccines for decades, and other mRNA vaccines have been in research and development since 1995. The authorized vaccines for COVID-19 underwent the same rigorous approval process as other vaccines.
Vaccine manufacturers are required to follow guidance issued by the Food and Drug Administration (FDA) when developing any vaccine, including COVID-19 vaccines. Each is required to provide their clinical trial data to the FDA, which the FDA and other experts use to conduct a thorough review of the vaccine’s safety and efficacy before authorizing it for use. The results of all COVID-19 vaccine clinical trials are reviewed by over 50 independent experts by the time the vaccine is authorized. The authorized vaccines will be continuously monitored through many different safety systems to ensure the vaccines' safety. Many of these systems have existed for decades and work well to ensure that the benefits of vaccination continue to outweigh any risks.
No safety steps were passed over to make the COVID-19 vaccine available as quickly as it was. Phase I trials were either combined with or replaced by Phase II trials, which just involve different numbers of people in clinical tests. Manufacturers also made the vaccine 'at-risk,' meaning they would have lost money if the vaccine did not work, a step that is usually not taken except in extreme circumstances like the COVID-19 pandemic. Different groups also sped up their logistics planning to make sure the vaccine could be distributed to vulnerable groups as soon as an emergency use authorization was granted by the FDA.
Trials for all vaccines currently authorized for use in the U.S. included people from all communities to closely match the demographics of the U.S. population and ensure representation from different age groups, races and ethnic backgrounds.
In the Pfizer/BioNTech clinical trials, there were over 44,000 participants over the age of 16. The trial for 12 - 15 year olds included 2,260 adolescents. The trial for 5 - 11 year olds included 2,268 children. About 30% of U.S. participants in the Pfizer trials were from racial and ethnic minorities, and about 45% of U.S. participants were between 56 – 85 years of age.
In the Moderna trials, there were over 28,000 participants. 37% of participants were from racial and ethnic minorities, 7,000 participants were people age 65 and older, and over 5,000 participants were younger people with chronic diseases like obesity, cardiac disease and diabetes.
In the J&J trials, there were about 40,000 participants. About 20% of trial participants were 65 years and older, about 45% were Hispanic or Latinx, about 17% were Black or African American, about 8% were American Indian or Alaska Native, and about 40% had at least one medical condition like obesity or high blood pressure.
The Novavax vaccine trials included about 30,000 participants. 20% of all participants were Hispanic or Latinx, 12% were Black or African American, 7% were American Indian or Alaska Native, and 5% were Asian American. 13% of participants were 65 or older.
In rare cases. The J&J vaccine was previously linked to a rare kind of blood clot experienced in the weeks following vaccination. Distribution of the J&J vaccine was temporarily paused to investigate these reports. After the pause was lifted by the Advisory Committee on Immunization Practices (ACIP), scientists continued to study the risk. The rate of this side effect was found to be approximately 1 case in 100,000 doses in the highest risk group (women between 30-49). Out of 14 million doses, only 54 total individuals have experienced these blood clots.
In 2021, ACIP voted unanimously to update their guidelines to recommend the Pfizer and Moderna vaccines over the J&J vaccine due to their greater effectiveness and the limited risk of blood clots from the J&J vaccine. Those who have already received the J&J vaccine or a J&J booster are not at risk if more than 42 days have passed since their dose and they have not experienced any symptoms. Those who have not received a booster yet should seek a Moderna or Pfizer booster dose.
If you have already received the J&J vaccine, the benefits of the J&J vaccine still far outweigh the risk of a rare side effect like this. The pause and thorough review of the vaccine's safety and efficacy proves that vaccine safety monitoring systems are working, and that safety is a top priority. There is no concern about this adverse event in people who have received the Moderna, Pfizer, or Novavax vaccines. For additional information, please visit Vaccinate Your Family's website.
In 2022, the FDA limited the use of the J&J vaccine to individuals 18 and up for whom other vaccines are not accessible or appropriate and to those who would otherwise not receive a COVID-19 vaccination. This action was taken due to the risk of thrombosis with thrombocytopenia syndrome, or TTS. It can cause blood clots which can be dangerous. The Pfizer and Moderna vaccines are preferred over the use of the J&J vaccine due to the very rare occurrence of TTS.
In rare cases. You may have heard that a small number of teens and young adults (about 140 out of 1 million doses of vaccine given) have experienced cases of mild heart inflammation, myocarditis and pericarditis, after getting an mRNA COVID-19 vaccine (Pfizer or Moderna). The cases were observed mostly in older teens and young adults, more often in males, more often after the second dose of vaccine, and within four days following vaccination. The FDA is continuing to study this rare side effect from mRNA vaccines in newly authorized populations. Data from the Novavax clinical trials show that out of nearly 30,000 participants there were six cases of myocarditis, primarily among males. The six individuals all recovered. The risk of developing myocarditis from COVID-19 infection is greater than from a COVID-19 vaccine. While heart issues can seem scary, myocarditis and pericarditis can be mild and treatable. People with or parents whose children have a history of myocarditis or pericarditis can choose to consult with their doctor before getting vaccinated. There is no known additional risk to teens who play sports or exercise regularly.
You may have heard that a small number of people have reported developing Guillain-Barré syndrome (GBS) following vaccination with the Johnson & Johnson vaccine, out of 12.5 million doses administered in the U.S. Although the available evidence suggests some association between the J&J vaccine and GBS, it is not enough to establish a causal link. The FDA has reviewed the cases and determined that the known benefits of J&J vaccine continue to outweigh the known and potential risks. The FDA has issued a revised Johnson & Johnson (Janssen) COVID-19 Vaccine EUA Fact Sheet to include information about GBS and notes that vaccine recipients should seek medical attention right away if they develop any GBS symptoms after receiving the J&J COVID-19 Vaccine. Every year in the U.S. an estimated 3,000 - 6,000 people develop GBS and most recover fully. The FDA will continue to monitor reports of GBS following vaccination.
No. Scientists agree that the COVID-19 vaccines do not impact puberty or fertility in females or males, now or at any time later in life. Producing mRNA is a part of our cells' natural processes. The mRNA vaccines teach our cells to make a harmless piece of spike protein that looks like, but is not, the COVID-19 coronavirus. This is so that our body builds antibodies for COVID-19 and can fight off future COVID-19 infections. It’s biologically impossible for those antibodies to attack other kinds of proteins that would in turn affect eggs, sperm, or cells in the reproductive organs. And COVID-19 vaccines are strongly recommended by the CDC for pregnant people. Pregnant people who become infected with COVID-19 are 15 times more likely to die and 22 times more likely to have pre-term births than pregnant people not infected. COVID-19 vaccines are safe for pregnant people, and can drastically reduce the risk of adverse pregnancy and neonatal outcomes.
Are the Vaccines Effective?
The available vaccines are very effective.
In clinical trials, both the Moderna and Pfizer vaccines demonstrated over 94% efficacy with two doses in adults, and Pfizer showed 90% efficacy in children 5-11 and 12-17. Moderna showed 89% efficacy in children 12-17 and 80% in children 6-11. For children 6 months to 5 years, Pfizer showed 73% efficacy while Moderna showed 51%.
The J&J vaccine demonstrated 85% efficacy at preventing severe cases of COVID-19 and 66% efficacy at preventing moderate and severe disease.
The Novavax vaccine demonstrated 90% efficacy in preventing mild to moderate infection.
All of the vaccines were shown to be effective at preventing hospitalizations and death due to COVID-19. However, no vaccine is 100% effective, which is why it's important to continue practicing other disease-prevention measures like wearing a mask in public, washing your hands and maintaining distance from those outside your household until enough of the community is vaccinated to offer community immunity.
COVID-19 vaccines are incredibly effective, but they aren’t 100%. We know from clinical trials in adults over 18 that Moderna and Pfizer are 95% effective and Novavax is 90% effective, which is very high, but means that some people could get COVID-19 even if they are vaccinated. If you do get COVID-19 after being vaccinated, your risk of getting severely ill, being hospitalized, or dying is very low. All COVID-19 vaccines are very effective at preventing severe illness leading to hospitalization and death–especially for people who have had a booster shot–even with the more contagious Omicron sub-variant strains circulating widely.
All COVID-19 vaccines currently offered in the U.S. have been shown to be highly protective and effective at preventing hospitalization and death due to COVID-19. Getting vaccinated and staying up to date with boosters are some of the most effective tools for keeping yourself protected and helping stop the spread of COVID-19.
However, the mRNA vaccines and Novavax vaccine are preferred over the J&J vaccine. The FDA has limited the use of the J&J vaccine to individuals 18 and up for whom other vaccines are not accessible or appropriate and to those who would otherwise not receive a COVID-19 vaccination. This action was taken because of the risk of thrombosis with thrombocytopenia syndrome, or TTS. In rare cases, it can cause blood clots which can be dangerous. The Pfizer, Moderna and Novavax vaccines are preferred over the use of the J&J vaccine due to the very rare occurrence of TTS. Additionally, these vaccines offer better protection against COVID-19 than J&J.
COVID-19 vaccine protection is thought to last about 6 months. As protection wanes and new variants of the virus arise, it is important to restore protection with booster doses of COVID-19 vaccine. Following the CDC’s guidance on booster doses of COVID-19 vaccines is crucial to maintaining immunity and avoiding severe illness, hospitalization, and death. It is also important to continue disease prevention habits like wearing a mask and physically distancing from others when appropriate.
Viruses change constantly to create new variants. COVID-19 vaccines offer strong protection against severe illness, hospitalization, and death, but may not always prevent infection. This has been the case with the currently circulating Omicron sub-variants, BA.4 and BA.5. The CDC recommends that everyone over 6 months of age get vaccinated for COVID-19 and those over age 5 stay current with booster doses. Getting vaccinated is still the best way to protect against the virus and keep from spreading it to others.
The CDC recommends that individuals who are at high risk for severe illness wear a well-fitted mask or respirator. Individuals who are in contact with those who are at high risk should also mask in indoor settings and additionally seek testing before coming into physical contact with those at high risk. While masking is no longer a requirement in many environments, it remains an effective way to stop the spread of COVID-19. Individuals may choose to continue masking in indoor settings and in areas with higher rates of infection.
COVID-19 Vaccine Information in Multiple Languages*
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For additional information and answers to other common questions, visit CDPHE's COVID-19 Vaccine FAQ.