Frequently Asked Questions

About the Vaccines

What types of COVID-19 vaccines are available?

Currently, the U.S. Food and Drug Administration (FDA) has authorized three COVID-19 vaccines from the companies Pfizer, Moderna, and Janssen (Johnson & Johnson). The FDA authorized the Pfizer vaccine for people 12 years and older and authorized the Moderna vaccine and Janssen (Johnson & Johnson) vaccines for adults 18 and older.

The CDC provides detailed profiles for each available vaccine on its "Different COVID-19 Vaccines" webpage.

What are the major differences between mRNA vaccines (Pfizer and Moderna) and viral vector vaccines (Janssen/Johnson & Johnson)?

All authorized COVID-19 vaccines teach your body how to make spike proteins like the ones that cover the COVID-19 virus. Your body learns how to fight the spike protein without having to fight off the full virus. If you are exposed to a person with COVID-19 after vaccination, your body will recognize the spike proteins and remember how to fight them before the virus makes you sick.

All COVID-19 vaccines contain instructions for how to make spike proteins, but these instructions are written in different ways. Viral vector vaccines, like the Janssen (Johnson & Johnson) vaccine, use a piece of double-stranded DNA to teach your body how to fight COVID-19. mRNA vaccines, like the Pfizer and Moderna vaccines, use single-stranded mRNA. The goal of every vaccine is the same — they just use a different strategy to achieve that goal.

Janssen’s (Johnson & Johnson) vaccine is more durable than either of the authorized mRNA vaccines. It can be stored for up to three months at normal refrigeration temperatures (36–46°F or 2–8°C).

The Janssen (Johnson & Johnson) vaccine only requires one dose. The Pfizer and Moderna vaccines require two doses.

Is one type of vaccine recommended over the other?

None of the vaccines is recommended over the other for adults 18 and over. Children age 12 to 17 can currently only get the Pfizer vaccine. If you are an adult, we encourage you to get whichever vaccine type or product is offered to you. Getting vaccinated greatly reduces the risk of illness if you are exposed to the virus, regardless of the manufacturer of the vaccine. 

How many doses are the COVID-19 vaccines?

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

The Pfizer and Moderna COVID-19 vaccines require two doses. Pfizer doses should be given 21 days apart and Moderna doses should be given 28 days apart. If it isn’t possible to get the second dose on the right day, the second dose can be given early, up to 4 days before it is due. Additionally, the second dose can be given as late as 42 days (6 weeks) after the first dose. COVID-19 mRNA vaccines are not meant to be not interchangeable. The second dose of any COVID-19 vaccine should be completed with the same vaccine product as the first dose. 

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 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 prompt the body to 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 (ModernaPfizer, or Janssen).

Do any of the vaccines contain ingredients that would be prohibited by my faith?

Janssen’s (Johnson & Johnson) vaccine includes ethanol, a form of alcohol, as an inactive ingredient. 

None of the currently authorized vaccines contain human cells or tissue. However, some human cell lines were used in the production of Janssen’s vaccine. 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. As with all viral vector vaccines, multiple purification steps ensure that cells are not in the final vaccine product.

If you have ethical concerns about the vaccines, we encourage you to talk to your faith leaders about them.

Getting a Vaccine

Who can get a COVID-19 vaccine and when?

Right now, all Coloradans age 12 and older are eligible to receive the Pfizer vaccine, and all Coloradans age 18 and older are eligible to receive the Moderna or Janssen (Johnson & Johnson) vaccine. 

To find a vaccine provider near you, go to the "Where to Get a COVID-19 Vaccine" webpage.

Anyone younger than 12 years old should not get a COVID-19 vaccine unless they are enrolled in a clinical trial. 

How do I set up an appointment to get a vaccine?

There are dozens of vaccine providers across Weld County, many of which don't require appointments. Go to the "Where to Get a COVID-19 Vaccine" webpage to find a vaccine site near you. 

The state-run mobile vaccine buses are making frequent stops across Weld County, as well. You can find upcoming stops and book an appointment online

If you need further assistance finding a vaccine site near you, please call the Weld County Health Department at (970) 304-6420.

Can the vaccine cause an allergic response?

Although it is rare, the COVID-19 vaccines may cause mild allergic reactions in some people, like itching or rash. Extremely rarely, some people may have a severe allergic reaction like anaphylaxis. If this occurs, vaccine providers can effectively an immediately treat the reaction.

Anaphylaxis after receiving a COVID-19 mRNA vaccine is rare and occurs in approximately 2-5 people for every 1 million vaccinated, based on events reported to Vaccine Adverse Event Reporting System (VAERS). Similar data are not available yet for the Janssen (Johnson & Johnson) vaccine.

The health care provider administering your vaccine will monitor you for any allergic reactions you may have after getting vaccinated. They will watch you for at least 15 minutes after the injection (or for 30 minutes if you have a history of anaphylaxis or if you have had an immediate allergic reaction of any severity to a vaccine or injectable therapy).

If you had a reaction following a vaccination, contact your health care provider. You can also submit a report to VAERS.

Can I get COVID-19 from the vaccine?

No. The vaccines don't contain the COVID-19 virus, and it is not possible to get COVID-19 from a vaccine. 

You may feel some side effects like fever, chills, and fatigue. The current COVID-19 vaccines use temporary pieces of genetic code from the virus to stimulate your body’s immune response. This cannot cause COVID-19. The goal of each vaccine is to provide your body with the tools it needs to fight the COVID-19 virus if you were to get infected.

If I have recovered from COVID-19, do I still need to get a COVID-19 vaccine?

Yes. We recommend that you get a vaccine even if you previously had COVID-19 and recovered.

Scientists are still learning more about how long you might be immune after recovering from COVID-19. Early evidence suggests natural immunity from COVID-19 may not last very long in some people, and cases of reinfection have been reported.

People with known current COVID-19 should wait until they have recovered (if they had symptoms) and they have met criteria to discontinue isolation. This recommendation applies to people who get COVID-19 before receiving any vaccine dose and those who get COVID-19 after the first dose of an mRNA vaccine but before the second dose.

While there is no recommended minimum interval between infection and vaccination, current evidence suggests the risk of reinfection is low in the months after initial infection but may increase with time due to waning immunity. 

How much does a COVID-19 vaccine cost?

The vaccine is free. Providers should not ask you to pay for the vaccine or other administrative costs,  even if you don’t have health insurance. If you do have insurance, your provider may seek reimbursement from your health insurance company, but you should not be charged. 

In the unlikely event that your provider requires payment for your vaccine appointment, you should ask questions about what you are being charged for and why. You should ask for an itemized bill or receipt from the provider and then seek reimbursement from your insurance company if you have one.

If someone is making you pay for a vaccine or a vaccine appointment, it may be a scam. You can report potential vaccine scams to the Colorado Attorney General’s Office at

Do I need to be a U.S. citizen to get a vaccine?


You do not need to be a U.S. citizen, and you do not need to prove lawful presence to get a COVID-19 vaccine in Colorado. State and local public health agencies will never share your information for any immigration or law enforcement purposes. And receiving the COVID-19 vaccine will not count against you in any public charge determinations.

Know that the Department of Homeland Security announced that vaccination sites will be considered sensitive locations. This means ICE will not carry out enforcement activities at or near vaccination sites. 

You do not need a government-issued ID like a driver's license or passport to get the vaccine. Some medical forms may have a field to enter your social security number, but you are not required to provide it.

How much personal information will I have 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. Some medical forms may have a field to enter your social security number, but you are not required to provide it.

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.

Sharing your identity and some of your medical history ensures 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 submits daily, 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.

Will I be required to get a COVID-19 vaccine?


Getting a COVID-19 vaccine is a personal choice. 

The state is not considering a COVID-19 vaccine mandate at this time.

Side Effects

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. 

The process of building immunity can cause symptoms. 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.

If you experience discomfort after the first dose of the Pfizer or Moderna vaccine, it is very important that you still receive the second dose a few weeks later for full protection.

Are the vaccine side effects worse after the second dose?

The side effects after the second dose of a Pfizer or Moderna vaccine might be more intense or cause more discomfort than side effects after the first dose. In some cases, the side effects may be bad enough to interfere with your work and other normal daily activities for a day or two. 

If you are experiencing more intense side effects, stay well hydrated, rest, and consider over-the-counter medications like acetaminophen or ibuprofen (if they are normally safe for you to take). Side effects are proof that your body is building immunity in response to the vaccine and will typically go away on their own within a day or two. 

Even if you experience discomfort from the vaccine, it is important that you receive both doses for full protection.

Why would the side effects be worse after the second dose?

Because the body has already responded to one dose of the vaccine, the second dose may cause a stronger immune response in your body. These side effects are expected and show that your body is continuing to build immunity. 

It is OK if you do not feel any side effects; it doesn’t mean the vaccine isn’t working.

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.

Are there any serious side effects of receiving a 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. 

The 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. 

Vaccine Safety and Development

Are the COVID-19 vaccines safe?

 All authorized COVID-19 vaccines have gone through the most intense safety monitoring in U.S. history. Millions of people in the U.S. have safely received a vaccine and are now protected from COVID-19.

The FDA requires vaccines undergo a rigorous scientific process, including three phases of clinical trials, before they authorize or approve the vaccine. The COVID-19 vaccines are subject to the same safety standards as other vaccine trials. Tens of thousands of people volunteered in these trials to help make sure the vaccines are safe and work well.

After the clinical trials, two independent advisory committees review a vaccine’s safety data before it is made available to the public. These committees are the Vaccines and Related Biological Products Advisory Committee (VRBPAC), which advises the FDA, and the Advisory Committee on Immunization Practices (ACIP), which advises the CDC.

Who approves vaccines in the U.S.?

The Food and Drug Administration (FDA) licenses and approves the use of all 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 licensed 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 were the vaccines able to get developed so quickly?

In developing a vaccine for COVID-19, researchers had to work quickly, but not at the risk of anyone’s safety. Medical 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 inform a vaccine development process for COVID-19.
  • Everyone involved dedicated all their resources and time to developing a COVID-19 vaccine. This includes research institutions, pharmaceutical companies, government agencies, and philanthropic organizations.
  • Many governments around the world, including the U.S. government, and private funders invested in the vaccine, which allowed pharmaceutical companies to focus on research right away.
  • Because of the financial support, researchers were able to conduct different parts of the development process on parallel tracks instead of one after another. Usually, each phase in a clinical trial ends before the next phase begins, with several months to a year or more in between each phase. 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.

How is vaccine safety monitored after it's been approved or authorized?

The FDA and CDC continue to closely monitor vaccine safety after the public begins using the 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:

  • CDC’s V-SAFE is a new smartphone-based, after-vaccination health checker for people who receive COVID-19 vaccines. Vaccine recipients can opt-in to receive text messages and web surveys from CDC on how to report health problems following COVID-19 vaccination. The system will also provide telephone follow-up to anyone who reports medically significant adverse events. The report will be submitted to the Vaccine Adverse Event Reporting System (VAERS) while keeping patient identity confidential.
  • Vaccine Adverse Event Reporting System (VAERS) is an early-warning system that 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.

After Getting a Vaccine

When will I be protected after I get the vaccine?

Studies show it takes about one to two weeks after your last dose for your body to be able to protect itself against illness. People are considered fully vaccinated: 

  • 2 weeks after their second dose in a 2-dose series, like the Pfizer or Moderna vaccines
  • 2 weeks after a single-dose vaccine, like the Janssen (Johnson & Johnson) vaccine.

While no vaccine is 100% effective, Pfizer and Moderna have reported their vaccines are about 95% effective when taken on schedule.

Do I still need to wear a mask and physical distance after getting the vaccine?

If you are fully vaccinated, you do not need to wear a mask or distance in most places, except where required by federal, state, local, tribal, or territorial laws, rules, and regulations, including local business and workplace guidance. You can go back to doing many of the things you did before the pandemic.

Do I need to quarantine from possible exposure after I've been fully vaccinated?

Most fully vaccinated people with no COVID-like symptoms do not need to quarantine, be restricted from work, or be tested following an exposure to someone with suspected or confirmed COVID-19, as their risk of infection is low.

If you are fully vaccinated and work in a congregate setting or other high-density workplace and have no COVID-like symptoms, you do not need to quarantine following an exposure. However, CDC recommends getting tested after an exposure.

Whether or not you are in quarantine, watch for symptoms in the 14 days after exposure and get tested if you start to develop symptoms. If you test positive, you will need to isolate. Note that PCR test results will not be affected by the vaccine. A positive PCR test generally indicates recent COVID-19 infection.

Do I need to isolate if I develop COVID-19-like symptoms after I've been fully vaccinated?

Yes. If you develop COVID-19 symptoms at any time after being fully vaccinated, you should isolate and contact your health care provider for instructions on whether to be tested for COVID-19 or other infections. 

If you experience the expected side effects after receiving a vaccine, it likely means that you are not contagious and do not need to isolate. Side effects typically occur one to two days after receiving the vaccine and can include fever, chills, headache, and fatigue. Cough, shortness of breath, nasal congestion, sore throat, or loss of taste or smell are not recognized side effects of the vaccine and may be signs of COVID-19 infection (or another infection).

Can a business check my vaccination status before allowing me onto the property?


The federal Health Insurance Portability and Accountability Act (HIPAA) does not apply to businesses like retail stores and restaurants because these businesses do not engage in any form of health care activity. It is not a violation of any federal or state law for a business to ask customers about their vaccination status. Customers may voluntarily share this information with a business if they choose to do so. A business may require public health measures (e.g. mask-wearing) if a customer chooses not to share their vaccination status.  

Can public and private sector employers mandate employees get a COVID-19 vaccine?

Employers may be able to require COVID-19 vaccination for in-person work for their employees, but an employee may be entitled to an exemption through the ADA and Civil Rights Act of 1964. The state of Colorado is not currently pursuing any mandates. 

Employees who work for employers requiring COVID-19 vaccination and who wish to exercise an exemption from the COVID-19 vaccine should consult with their human resources office on acceptable exemption forms. 

Can public and private colleges and universities mandate COVID-19 vaccination for students, faculty, and/or staff?


Questions regarding COVID-19 vaccination requirements for students, faculty and/or staff should be directed to the specific college or university.

Booster Doses

Who can get a booster dose?

COVID-19 vaccine booster shots are now available to eligible individuals who completed an initial series (2 doses) of the Pfizer or Moderna vaccine at least 6 months ago AND are:

  • 65 years and older
  • Age 18+ who live in long-term care settings
  • Age 18+ who have underlying medical conditions
  • Age 18+ who work in high-risk settings
  • Age 18+ who live in high-risk settings

Booster shots are also recommended for Johnson & Johnson vaccine recipients:

  • 18 years and older
  • Who were vaccinated 2+ months ago

When should I get a booster dose?

If you received the Pfizer or Moderna COVID-19 vaccine and you are eligible, you should receive your booster dose at least 6 months after your second dose, no matter what kind of vaccine you get as a booster.

If you received the Johnson & Johnson COVID-19, you can get a booster dose at least 2 months after your initial dose, no matter what kind of vaccine you get as a booster.

Why do I need a booster dose?

The vaccines continue to work well, but booster doses can help give you extra protection from COVID-19 if you are at high risk of getting very sick. Vaccine effectiveness may decrease over time and a booster dose can help raise immunity levels. With delta variant circulating and cases of COVID-19 increasing significantly across the United States, a booster will help protect people who are most at risk. Booster doses are common practice in routine childhood vaccines and require multiple doses at specific intervals to be most effective. You are still considered fully vaccinated if you don't receive a booster shot.

Where can I get a booster dose?

You can get a booster dose at any vaccine provider that has COVID-19 vaccine. No ID, insurance, or proof of medical history is required. Booster doses are free. You may self-report having a high risk condition to vaccine providers.

Does my booster shot have to be the same kind of vaccine as my initial dose(s)?

No. Eligible individuals may choose which vaccine they receive as a booster dose. Some people may prefer the vaccine type that they originally received, and others may prefer to get a different booster. CDC’s recommendations now allow for this type of mix and match dosing for booster shots.