COVID Risk Quiz FAQs

Visit the US Department of Health and Human Services website to find a testing site near you.

Every home in the US may order free at-home COVID-19 tests from the federal government. Orders can be placed at covidtests.gov or 1-800-232-0233 (TTY 1-888-720-7489). The Rockefeller Foundation is also offering free at-home COVID-19 tests to individuals in certain ZIPcodes through their Project ACT program while supplies last.

You can purchase over-the-counter at-home COVID-19 tests at many pharmacies and other retail oulets, as well as online. Private commercial health insurance will reimburse you for up to eight tests per person per month purchased online or in stores. Check with your insurance provider for their reimbursement policy.

Military beneficiaries can get up to eight free tests per month at military hospitals or clinics.

People with Medicare Part B can get up to eight free rapid tests per month at health-care facilities and participating pharmacies.

You can also contact your health-care provider, your local community health center, or your state or local public health department for more information.

The COVID Risk Quiz is a tool intended to help you decide whether you should get tested for COVID-19 in order to keep from spreading the disease to other people. If you get this recommendation, your risk of spreading the disease will be lowest if you get tested before coming into close contact with anyone outside your household. (This Quiz is a decision-support tool only. Results are provided for informational purposes and should not be construed as medical advice.)

CDC — Self-Testing At Home or Anywhere

If you've been infected with SARS-CoV-2 (the virus that causes COVID-19), your risk of getting infected again is lower for a period of time. However, it's not clear exactly how much lower that risk is; it might depend on how severe your case was and what variant you were infected with. It's also not clear how long the protection lasts.

For those reasons, the COVID Risk Quiz assumes that prior infection only gives you a relatively small amount of protection from future disease, and that the protection is temporary.

CDC — Reinfections and COVID-19

Screening for COVID-19, also referred to as screening testing or asymptomatic screening, means testing your population to identify infected people who are not showing symptoms. Diagnostic testing for COVID-19 is performed when infection is suspected, such as when the person:

• Has COVID-19 symptoms or

• Has no symptoms, but has had a recent known or suspected exposure to SARS-CoV-2 (the virus that causes COVID-19).

Asymptomatic screening is typically a regularly scheduled event (e.g., 1x/week). Along with other COVID-19 mitigation strategies, screening can help prevent outbreaks in your school or workplace.

Not many tests have authorization from the FDA specifically for screening testing. However, the FDA supports the use of COVID-19 tests that have Emergency Use Authorization (EUA) when used “off-label” under the supervision of a physician or other prescriber.

NOTE: The Workplace Testing Planner and the COVID Risk Quiz assume that tests that do not have FDA authorization for screening are used off-label under practitioner guidance.

Both kinds of testing can be done using either a PCR test (also known as a molecular or lab test) or an antigen test (also called a rapid test).

PCR tests look for pieces of the virus’s genetic material. They are the most accurate kind of test for COVID-19 currently available.

Antigen tests look for proteins from the virus. They are designed to be taken twice: You take one test now, and one test a day or two later. When used that way, they are nearly as accurate as PCR tests. If you're using antigen tests for screening, you'll need to test more frequently than you would if you were using PCR tests.

Antibody tests (also known as serology tests) look for proteins that your body makes to fight the virus. Those proteins are called antibodies. They can come from a past COVID-19 infection or from a COVID-19 vaccine. Antibody tests cannot be used to diagnose an active infection.

FDA – Coronavirus 2019 Test Basics

CDC – Nucleic Acid Amplification Tests (NAATs)

CDC – Guidance for Antigen Testing for SARS-CoV-2 for Healthcare Providers Testing Individuals in the Community

In point-of-care (POC) testing, all testing steps, including sampling and analysis, take place close to or near the patient. For the Workplace Testing Planner and the COVID Risk Quiz, this means that testing is completed either on-site at your organization’s location or in a health-care provider's office, at a testing site, or in your home. Point-of-care tests give you results quickly. Most of them are antigen tests, but some point-of-care PCR tests are available, as well.

In lab-based or off-site testing, samples are gathered on-site at your organization or other testing location and are sent to a central lab for processing and analysis. Lab-based tests are generally PCR tests, which are highly accurate. However, they take longer to return results than point-of-care tests do. In some cases, the turnaround time of lab-based tests is not fast enough to prevent an outbreak in an organization. 

CDC – Guidance for SARS-CoV-2 Point-of-Care and Rapid Testing

CDC – Self-Testing At Home or Anywhere

Sensitivity refers to how well a test designates someone who HAS the disease as positive.

If you have a test with 95% sensitivity and you test 100 people who have COVID-19, 95 will test positive (true positive) and 5 will test negative (false negative). Tests with high sensitivity will find most cases of the virus. They will return few false negatives.

Specificity is how well a test designates someone who DOESN’T have the disease as negative.

If you have a test with 95% specificity and you test 100 people without COVID-19, 95 will test negative (true negative) and 5 will test positive (false positive). People who test positive using tests with high specificity are very likely to truly have the disease, which means that very few people will be quarantined unnecessarily. These tests return few false positives.

In an ideal world, all tests would be both highly sensitive and highly specific. Unfortunately, that’s not possible most of the time. It’s also important to acknowledge that no test is perfect — no test will have 100% sensitivity and specificity.

When you're using a test to find out if someone has a disease, there are four possible results you can get:

• True positive: The test result is positive and the person has the disease.

• True negative: The test result is negative and the person doesn't have the disease.

• False positive: The test result is positive but the person doesn't have the disease.

• False negative: The test result is negative but the person does have the disease.

In an ideal world, all tests would return only true positives and true negatives. Unfortunately, no test is perfect. 

PCR tests, also known as molecular tests, look for pieces of the virus’s genetic material using a lab technique called polymerase chain reaction (PCR). They are the most accurate kind of test for COVID-19 currently available.

PCR samples are usually sent for processing and analysis in a lab, and results can take anywhere from a few hours to several days to arrive. Lab-based PCR tests tend to cost more than other test types. Some point-of-care PCR tests are now available, but they typically require purchase of a dedicated instrument and training to run the tests. If you want to use a point-of-care PCR test to screen members of an organization, you may need to purchase multiple instruments and train several staff members for this purpose. Point-of-care PCR tests typically return results in under an hour.

Antigen tests look for viral proteins. These tests typically provide results within minutes and are very good at accurately identifying people who are carrying a lot of virus. They are not as good as PCR tests are at finding people who aren't carrying as much virus, including children and asymptomatic adults. If your organization is using this type of test, check how well the brand you use works in the population you’ll be testing (adults vs. children, people with symptoms vs. people without symptoms). Many antigen tests still require trained staff run them, but others are now available over the counter for home use. Antigen tests tend to be the least expensive type of test.

Because of their decreased sensitivity, antigen tests have the following limitations:

• If you are using antigen tests to screen members of an organization, you may need to test more frequently than you would if you were using a PCR test in order to prevent an outbreak.

• If you have symptoms or were recently around someone with COVID, a positive result on an antigen test is usually correct, but a negative test result might not be right. If you just got infected, you may not have enough virus in your system for a rapid test to detect.

• Once your virus levels have gone up, a rapid test will show a positive result. That’s why home tests are usually sold in packs of two.

• It’s best to take the second test 24 - 48 hours after the first. The amount of time you should wait varies depending on the brand of test. You can also get a lab test to confirm your result.

• Be sure to follow all of the instructions that came with the test.

Remember, no test is perfect. 

FDA — Coronavirus 2019 Test Basics

CDC — Guidance for Antigen Testing for SARS-CoV-2 for Healthcare Providers Testing Individuals in the Community

CDC — Self Testing At Home or Anywhere

Antibodies are proteins created by your immune system to help you fight off infectious microbes. Your body makes them after you’ve been infected or vaccinated.

Antibody tests (also known as serology tests) look for antibodies to SARS-CoV-2 (the virus that causes COVID-19). They cannot be used to diagnose an active COVID-19 infection, because it can take up to three weeks after the infection for your immune system to make antibodies. These tests can only be used to determine whether someone had COVID-19 or a COVID-19 vaccine in the past. 

The Food and Drug Administration (FDA) decides which drugs and medical tests can be used in this country. The full FDA approval process can take months to years.

When a public-health emergency happens, there isn’t time for new drugs or tests to go through the entire process. That’s when the FDA can use Emergency Use Authorization (EUA). It allows the FDA to let certain medical products be used more quickly, while still making sure they are as safe as possible. At a minimum, the product must have known and potential benefits that outweigh its known potential risks. In addition, there must be “no adequate, approved, and available alternatives” to the product receiving the EUA.

All treatments and tests for COVID used in the US have received an EUA - none of them have gone through the full approval process yet. The Pfizer and Moderna vaccines have received full approval from the FDA for adults. The Pfizer vaccine has an EUA for children ages 11 to 16.

FDA – Emergency Use Authorization

Variants are mutated forms of SARS-CoV-2, the virus that causes the disease COVID-19. The variants that cause concern are ones whose mutations make them more likely to spread from person to person, cause more severe disease, and/or are able to more easily infect people who have been vaccinated.

All COVID-19 tests that have Emergency Use Authorization (EUA) from the FDA must be checked on an ongoing basis to make sure that they are able to detect different variants of the virus. If a test has any difficulty detecting a variant, the FDA must be notified immediately.

NOTE: As part of its calculations, the Workplace Testing Planner includes a default measurement of how transmissible the virus is. That measurement is called R0 (“R-naught”) or the basic reproduction number for the virus. WhenToTest.org follows CDC guidance to set the Planner's default for R0. If you would like to set a specific R0 in your scenarios, you can do so under Advanced Settings: Main Planner Settings.

CDC — What You Need to Know About Variants

CDC — COVID-19 Pandemic Planning Scenarios 

FDA — EUA Letter of Condition - Viral Variant Revision

Isolation and quarantine have the same purpose: They help protect the public by preventing exposure to people who have or may have a contagious disease.

• Isolation keeps people who are definitely infected away from other people.

• Quarantine keeps people who were exposed to the virus away from others until they find out if they're infected.

CDC – Quarantine and Isolation

R0 (R-naught) is a measure of the average number of people who will contract a contagious disease from one infected person. It’s a measure of viral transmissibility, or how fast the disease is spreading.

When R0 is exactly 1.0, it means that, on average, one infected person will infect one other person. When R0 is less than 1.0, it means that the spread of the disease is decreasing within the community. When R0 is above 1.0, the spread of disease is increasing. The more transmissible a disease or disease variant is, the higher its R0.

CDC — COVID Data Tracker, Variant Proportions

CDC — What You Need to Know about Variants

World Health Organization — Tracking SARS-CoV-2 Variants

Johns Hopkins Medicine — COVID Variants - What You Should Know

Prevalence is the percentage of people in a population who have a disease. So if there are 100 people in your area and 10 of them have COVID-19, the prevalence of COVID-19 in your area is 10%.

Technically, the only way to determine the true prevalence of COVID-19 in a population is to test every single person in the population to see who has it and who doesn't. Since that's not feasible, the Workplace Testing Planner and the COVID Risk Quiz use a sophisticated machine-learning model that looks at all of the available COVID-19 data for a particular state and county and develops a "predicted prevalence" for that location.

For US territories and areas outside the US, the Planner and the Quiz use a prevalence of 1% for typical conditions, and 3% for hotspot conditions.

Both the Workplace Testing Planner and the COVID Risk Quiz are based on CDC guidelines. Current guidelines define a “close contact” as someone who was within six feet of an infected person for a total of at least 15 minutes over the course of 24 hours. One exception to that rule is applicable only to schools: Students who were between three and six feet of an infected person are not considered close contacts as long as they were in school and “correctly and consistently” wearing masks.

CDC — How to Determine a Close Contact for COVID-19 

All currently authorized COVID-19 vaccines are highly effective at preventing hospitalization, severe disease, and death due to COVID-19. People who are up to date on their vaccines are also less likely to become infected at all, which means they are less likely to spread COVID-19 than unvaccinated people are. For that reason, the number of contacts that would trigger a recommendation to get tested will be higher if you're fully vaccinated.

CDC — Vaccines for COVID-19

CDC — Stay up to Date with Your COVID-19 Vaccines

CDC — The Possibility of COVID-19 After Vaccination: Breakthrough Infections

The COVID Risk Quiz tells you whether you need to be tested in order to prevent the spread of COVID-19 in your community.  Wearing a mask significantly reduces both your risk of getting COVID-19 and the chance that you'll pass on the disease if you do get infected. As a result, the number of contacts that would trigger a recommendation to get tested will be higher if you wear a properly fitted mask when you're in close contact with other people.

The type of mask you wear also matters. Two-layer cloth masks have a filtration efficiency of about 30%. For surgical masks that fit well, without gaps, that number is about 70%. For KN95 masks, it’s about 85%. If you wear a high-efficiency mask, the number of contacts that would trigger a recommendation to get tested will be higher.

Find high-quality masks at Project N95.

CDC — Find Free Masks (N95 Respirators)

CDC — Use and Care of Masks

CDC — Types of Masks and Respirators

What you need to do depends on two things:

• Whether you're up to date on your vaccines.

• Whether you've had COVID-19 during the past 90 days.

Visit My COVID Toolkit for answers specific to your situation.

You'll need to isolate. If you're at high risk of getting very sick from COVID-19, you should consider getting treatment.

Visit My COVID Toolkit for up-to-date information on what to do when you test positive.

Yes. The Quiz uses an estimate of how well the vaccines available in the US protect against the variant that is currently dominant in the country. This estimate is based on the performance of all available vaccines, not on any one vaccine brand or type.

CDC – Monitoring COVID-19 Vaccine Effectiveness

The Quiz tells you whether you need to be tested in order to prevent the spread of COVID-19 in your community.

The number of people with whom you were in contact last week — along with the prevalence of COVID-19 in your area — tells the Quiz how likely it is that you have been infected with COVID-19.

The number of people with whom you plan to be in contact next week tells the Quiz how likely it is that you will infect other people.

The Quiz uses those factors and other inputs to develop a recommendation about whether you need to be tested in order to help stop the spread of COVID-19 in your area.

The COVID Risk Quiz uses two different parameters to tell you whether and when you need to get tested: 1) Your risk of having or getting infected with COVID-19, and 2) Your risk of spreading it to other people. It uses the prevalence of COVID-19 in your current location to help it determine how likely it is that you will get infected. It uses the number of people you plan to see next week to help it determine how likely it is that you'll spread the disease.

Given that, there are a couple of different ways you can handle this situation. One option would be to start by using the location you're in right now. Then recheck your results with the Quiz next week, using the location you're in at that time. When you check the Quiz this week, you'll find out if you need to get tested now, before you travel to your next location. By checking the Quiz again next week, you can find out if you need to get tested once you're in your new location.

Another option would be to run the Quiz two times right now, to see how your results might differ in one place versus the other. Just remember that the prevalence of COVID-19 in either location might change over the course of the week. When in doubt, come back to the Quiz to find out if your recommendation has changed.

The COVID Risk Quiz uses two different parameters to tell you whether and when you need to get tested: 1) Your risk of having or getting infected with COVID-19, and 2) Your risk of spreading it to other people.

The Quiz figures out how high your risks are based on four inputs. Three of those inputs are protective measures that you can take against COVID-19:

1. Vaccination

2. Masking

3. Distancing (The Quiz captures this information by asking about close contacts.)

The fourth input is the prevalence of COVID-19 in your area.

Prevalence is the percentage of people in a population who have a disease. So if there are 100 people in your area and 10 of them have COVID-19, the prevalence of COVID-19 in your area is 10%.

Technically, the only way to determine the true prevalence of COVID-19 in a population is to test every single person in the population to see who has it and who doesn't. Since that's not feasible, the Quiz uses a sophisticated machine-learning model that looks at all of the available COVID-19 data for a particular state and county and develops a "predicted prevalence" for that location.

The Quiz uses those "four pillars" - vaccination, masking, distancing, and predicted prevalence - and combines them with information about your behavior over the past seven days and what you expect your behavior to be over the next seven days. The result is a calculated estimate of the following:

• Your risk of getting COVID-19 over the past seven days.

• Your risk of getting COVID-19 over the next seven days.

• Your risk of spreading COVID-19 to others over the past seven days.

• Your risk of spreading COVID-19 to others over the next seven days.

Based on those four risk factors, the Quiz determines whether you should consider getting tested for COVID-19.

Note: If you are in a US territory or outside of the US, the Quiz asks if you are in a COVID-19 hotspot. If you are not in a hotspot, the Calculator assumes that the prevalence of COVID-19 in your location is 1%. If you are in a hotspot, it assumes that the prevalence in your area is 3%.

DataRobot — The company that developed the machine-learning model behind the COVID Risk Quiz.

The Planner and the Quiz have slightly different goals and base their recommendations on different inputs.

The goal of the COVID Risk Quiz is to reduce the spread of disease in a given geographic area at a specific time. It does that by recommending that an individual get tested when it's more likely that they might be about to pass COVID-19 on to others. (This Quiz is a decision-support tool only. Results are provided for informational purposes and should not be construed as medical advice.)

The goal of the Workplace Testing Planner is to decrease the overall risk of an outbreak within a workplace or school. It does that by evaluating the COVID-mitigation strategies in place at the organization and recommending the appropriate level of testing needed to complement those strategies.

For all of those reasons, when you use the two tools you might get different results. If your personal and organizational recommendations differ, consider taking both into account when deciding how often you should get tested for COVID-19.

You are in a COVID-19 hotspot if:

• There have been at least 100 cases of COVID-19 per 100,000 people in your area over the past seven days, and/or

• The test positivity rate in your area is currently 10% or higher. 

The number of cases per 100,000 people is called the incidence rate. If you are outside the United States, you can find your country's seven-day incidence rate here.

If you are in a US territory other than Puerto Rico, you can find your territory's incidence rate on this map in the CDC's COVID Data Tracker. Puerto Rico is on the drop-down list of US states in the Planner itself.