Frequently Asked Questions

  • See the list of providers above.
  • More information about provider settings and options for phase 2 and phase 3 recipients will be coming soon.
  • Sign up to receive an email when vaccine is available for your group within the state phased prioritization.
  • If you have general questions about COVID-19 vaccines, call 1-877-COVAXCO (1-877-268-2926).

  • Both the Pfizer and Moderna vaccines have been shown to be 95% effective in preventing COVID-19.
  • The Janssen vaccine has been shown to be 74.4% effective and 72% effective in preventing moderate to severe/critical COVID-19 occurring at least 14 days and 28 days after vaccination, respectively. Additional information about the Janssen vaccine can be found here.
  • Please note, it is not possible to make comparisons about the effectiveness among the three COVID-19 vaccines that the FDA has authorized for emergency use to date. The only way to accurately compare the effectiveness of medical products, such as vaccines or drugs, is by direct comparison in head-to-head clinical trials, which did not occur for these vaccines.
  • Once someone is vaccinated for COVID-19, their body should naturally develop antibodies that correspond with the virus and ward off future infection. It is still not clear how long those antibodies will last.

  • During December 14–23, 2020, monitoring by the Vaccine Adverse Event Reporting System detected 21 cases of anaphylaxis after administration of a reported 1,893,360 first doses of the Pfizer-BioNTech COVID-19 vaccine. Or roughly 11.1 cases of anaphylaxis per million doses.
  • The Pfizer application to the FDA includes two months of follow-up safety data from Phase 3 of clinical trials conducted by universities and other independent bodies.
  • Pfizer’s trial had 44,000 participants; no serious safety concerns have been reported.
  • Tens of thousands of people have already received the vaccines, and none of them have reported any serious health problems.
  • Trials: A diverse group of people participated in every phase of the clinical trials, including populations disproportionately impacted by COVID-19 due to generations of systemic inequities. For example, in Pfizer’s clinical trials, about 42% of volunteers identified as Asian, Black/African American, Hispanic/Latino/a, or Native American. About 37% of volunteers for Moderna's trials identified as Asian, Black/African American, Hispanic/Latino/a, or other.
  • On February 27, 2021, the U.S. Food and Drug Administration issued an emergency use authorization (EUA) for the third vaccine for the prevention of coronavirus disease

  • Currently, the U.S. Food and Drug Administration (FDA) has authorized three vaccines. The FDA authorized the Pfizer vaccine on December 11 for people 16 years and older and authorized the Moderna vaccine on December 18 for adults 18 and older. Both Pfizer and Moderna report that their vaccines are around 95% effective.
  • On February 27, 2021, the U.S. Food and Drug Administration issued an emergency use authorization (EUA) for the third vaccine for the prevention of coronavirus disease. Additional information about the Janssen vaccine can be found here.
  • Neither vaccine is recommended over the other. However, the vaccines are generally not interchangeable with each other or with other COVID-19 vaccine products. It is important that both the first and second dose are from the same vaccine manufacturer.
  • CDC provides detailed profiles for each available vaccine on their Different COVID-19 Vaccines page.

Both the Pfizer and Moderna COVID-19 vaccines require two doses. The Pfizer vaccine will require two doses 21 days apart; the Moderna vaccine will require two doses 28 days apart. COVID-19 vaccines are not interchangeable. The second dose of any COVID-19 vaccine must be completed with the same vaccine product as the first dose.

The Janssen (Johnson & Johnson) vaccine requires only one dose.

  • Until the vaccine is widely available and used, it is important to continue taking precautions to slow the spread of the virus, like wearing masks and practicing physical distancing.
  • At least initially, we expect that the COVID-19 vaccines will only be authorized for use in adults. Safety and effectiveness data from clinical trials is still needed before the vaccine is available for children or pregnant adults.
  • Stay up to date about vaccine distribution in Colorado at covid19.colorado.gov/vaccine.

  • Decades of vaccine research demonstrates that most serious side effects generally occur within six weeks of administering a vaccine. For the COVID-19 vaccines, the FDA has required clinical trials to provide data from eight weeks of safety monitoring following the second dose before considering the authorization of a vaccine for public use.
  • Because this is a new vaccine, researchers will be learning more about rare side effects, if any, over the next year. To identify side effects that happen only very rarely (e.g., once in 50,000 doses), hundreds of thousands of people need to be vaccinated and followed over time.
  • The FDA and CDC will continue to closely monitor vaccine safety as the public begins using a new vaccine. Both agencies have both longstanding and new safety systems in place for heightened monitoring of all COVID-19 vaccines. Learn more about the vaccine safety monitoring systems.

Because this is a new vaccine, researchers will be learning more about rare side effects, if any, over the next year. To identify side effects that happen only very rarely (e.g., once in 50,000 doses), hundreds of thousands of people need to be vaccinated and followed over time.

  • Science shows that generally the most serious side effects occur within six weeks of vaccine administration. The current available COVID-19 vaccines have been studied for longer than six weeks, and the companies have not identified or reported serious safety concerns. To date, the independent safety monitoring board overseeing Phase 3 trials of the Pfizer and Moderna vaccines has not found any serious safety concerns. The FDA will review all the research before authorizing the vaccine for use.
  • The FDA and CDC will continue to closely monitor vaccine safety as the public begins using a new vaccine. If safety monitoring reveals new information about vaccine risks, such as new serious side effects, a vaccine may be removed from the market. Learn more about the vaccine safety monitoring systems.

  • Your privacy is a top priority, and 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.
  • Sharing your identity and some of your medical history ensures that the vaccine is administered safely, effectively, and responsibly. Your 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.
  • The state health department will submit daily, anonymous COVID-19 vaccine administration data to the CDC as required. No personally identifiable information will be shared with CDC like your name or full address.

You do not need to be a U.S. citizen, and you will not need to prove lawful presence to get a COVID-19 vaccine in Colorado. Further, public health will never share your information with any immigration or law enforcement agency.

  • It will take time after the vaccination for your body to respond and make enough antibodies to protect you. This could take up to one to two weeks after your last dose.
  • Current info suggests that it is possible that someone who has been vaccinated against COVID-19 may still have a mild or asymptomatic infection or spread the virus to others. So it is important to continue taking precautions. Continue wearing masks and practicing physical distancing until it is clear that it is safe to stop.

Yes, if you develop COVID-19 symptoms after getting the vaccine should you quarantine. It typically takes a few weeks for the body to build immunity after vaccination. That means it is possible a person could be infected with the virus that causes COVID-19 just before or just after vaccination and gets sick. This is because the vaccine has not had enough time to provide protection. If you have COVID-19 virus symptoms after getting the vaccine or at any time, you should contact your health care provider and get tested for COVID-19.

Yes. Standard quarantine as advised by state and local health officials.

  • It is currently unknown how long natural immunity lasts after recovering from COVID-19.
  • Early evidence suggests natural immunity from COVID-19 may not last very long, and cases of reinfection have been reported.
  • Until the Advisory Committee on Immunization Practices makes recommendations on how to best use COVID-19 vaccines, we cannot comment on whether people who have had COVID-19 should get a COVID-19 vaccine.

The COVID-19 vaccines have gone through large clinical trials and have shown to be very effective in preventing symptoms of the disease. However, current information suggests it is possible that someone who has been vaccinated against COVID-19 may still have a mild or asymptomatic infection or spread the virus to others. Until we know more, it is important to continue taking precautions, like wearing masks and practicing physical distancing, even after you have been vaccinated.

In very rare cases, a vaccine can cause a serious problem, such as a severe allergic reaction. COVID-19 vaccines are covered under the Countermeasure Injury Compensation Program (CICP), not the National Vaccine Injury Compensation Program (VICP). The Public Readiness and Emergency Preparedness Act (PREP Act) authorizes the CICP to provide benefits to certain individuals or estates of individuals who sustain a covered serious physical injury as the direct result of the administration of COVID-19 vaccines.