About the Fight COVID MKE COVID-19 Individual Risk Estimator

COVID-19 is a disease that is caused by a coronavirus. This risk assessment tool gives estimates of your COVID risk for people similar to you, based on the information you provide. The tool is based on data through July 1, 2021.

Vaccination reduces your risk of becoming infected and greatly reduces your risk of becoming seriously ill from COVID. Vaccination also reduces the risk that you will infect other people. Serious side effects from vaccination are very rare and are far outweighed by reduced COVID risk. The graph below compares your risk if not vaccinated or previously infected to your risk if vaccinated. 

Vaccine boosters: Vaccine efficacy declines over time. Even if you were vaccinated, you will likely need a booster; the principal question is when. The Pfizer booster is currently approved by the FDA for persons over 65, adults at high risk for severe COVID infection, and adults in jobs that increase their risk for COVID infection. FDA action on boosters for the Moderna or Johnson & Johnson vaccines is pending.

Data Section: Please fill in the Basic Data and Health Data sections with information about you, or someone you are interested in learning about. The tool will complete the right-hand boxes based on the information you fill in.

COVID Risk Estimator Guide

We provide three sets of results, with answers to different questions. 

COVID Burden Box: This box shows our best estimates, using the information you provided, for:

  • Your life expectancy – how long someone like you will live, on average, with no COVID
  • The approximate percentage of people in your state who have been infected with COVID, including infection with no symptoms.
  • The proportion of people like you who have died from COVID
  • How much COVID has reduced life expectancy for people like you.

Estimates of life expectancy are for large groups of people. They are NOT predictions for individual people.

Graphs: The graphs to the right of the data section show how your expected loss of life expectancy, and risk of death, varies with the likelihood that you would become infected if not vaccinated and not previously infected, and also how vaccination can reduce your risk.

These risks are for the Pfizer vaccine; the Moderna vaccine should provide similar or better protection. The Johnson & Johnson vaccine provides somewhat less protection.

Comparing COVID to Other Risks: This box lets you compare COVID risk to other common risks. It shows, for people like you, how life expectancy is affected by car accidents, cancer, and flu and pneumonia (from causes other than COVID). This box compares the cumulative risk from COVID to date to one-year estimates of lost life expectancy loss from the other causes.

Where Does Risk Reduction Come From: The risks shown in the graph above are based on the best data available to us. We estimate the following reductions in risk, for persons who were previously infected, vaccinated, or both, relative to the risk (shown as equal to 1.00 for persons who are neither vaccinated nor previously infected.

Vaccination, or prior infection, reduces both your risk of being infected, the risk of severe infection, if you become infected, and your risk of infecting others. The table below provides are best current estimates of risk reduction for the Delta variant, which is currently the dominant COVID variant. However, data on risk from the Delta variant are still limited. Also, this table does not account for the decline over time in vaccine efficacy.

 Previously infected or vaccinated  No Yes
 Risk of any infection  1.00  0.20
 Risk of symptomatic infection  1.00  0.15
 Risk of hospitalization  1.00  0.10
 Risk of death  1.00  0.05
 Risk of infecting others 1.0   0.25

Some more details about the risk assessment tool:

For advice about your personal situation, please speak with your doctor or other healthcare professional. 

  1. Virus mutations. Coronavirus mutations can increase the risk of infection and reduce the degree of protection you receive from prior infection or vaccination. The Delta variant is highly infectious, and can be transmitted from unvaccinated to vaccinated people, and from one vaccinated person to another. We do not yet have good data on whether this variant causes more severe illness, if infected.

  2. Actual versus confirmed infections. Many more people were infected with COVID, than the number of confirmed infections. We rely on a Centers for Disease Control (CDC) national estimate of a 4.3 to 1 ratio of true infections to confirmed infections. The actual ratio varies depending on where you live.

  3. Risk of hospitalization. We think your risk of hospitalization is about 10 times your risk of dying of COVID, and perhaps more. But data are limited, so this is an estimate. There are not enough data to say how this risk varies with age or other personal factors, or with vaccination status.

  4. Risk after being vaccinated: The tool shows the reduced risk if you are vaccinated, starting 14 days after the second dose, for the Pfizer or Moderna vaccines. This is when these vaccines should be fully effective. The Johnson and Johnson vaccine requires only one dose and is also very effective in preventing severe illness, although likely somewhat less than the Pfizer or Moderna vaccines.

  5. Risk if you are vaccinated and were already infected: If you were both already infected and vaccinated, your risk of being infected again, or of having a serious infection, may be lower than from vaccination alone. However, there is not enough data on reinfections for people who were both vaccinated and already infected to know by how much.

  6. Vaccine safety. All available evidence is that the Pfizer and Moderna vaccines are highly safe and greatly reduce both your risk, and the risk that you will infect other people. Most side effects are minor. There is a small risk, for around 1 in 100,000 persons, of a severe allergic reaction to the shot. This is why people who are vaccinated are asked to wait for 15-30 minutes before leaving the vaccination site, so that any allergic reaction can be treated. There is also a small risk of heart muscle inflammation, seen mostly in young men, which is usually mild and goes away within a few weeks.

    For the Johnson & Johnson vaccine, there is a very small risk of developing potentially serious blood clots during the several weeks following vaccination. This risk is principally for women age 18-49, and for them is under 1 in 100,000 persons. There is also a small risk, principally for older men, of developing a nerve disorder called Guillain-Barre syndrome, which can cause temporary paralysis.

  7. Long-term symptoms. Some people can have long-term symptoms due to a COVID infection, including fatigue, cough, loss of taste or smell, and other symptoms. If you think you may have long-term COVID symptoms, please speak with a doctor.

  8. Effect of other diseases on COVID risk: Chronic diseases affect both your life expectancy without COVID. This is reflected in your expected years to live without COVID. Other diseases may also affect your COVID risk, but we do not know enough about how they affect COVID risk to take them into account in predicting your COVID risk.

For details on how we estimate life expectancy and COVID risk, see A COVID-19 Risk Calculator: Mortality Rates and Loss of Life Expectancy, at

About the Fight COVID MKE Project

This risk assessment tool was created by the Fight COVID MKE research team. MKE are initials for Milwaukee County, Wisconsin. However, the tool provides nationwide answers to COVID risk questions, which vary depending on where you live.

Lead researchers: The researchers who developed the risk assessment tool include, in alphabetical order, Vladimir Atanasov (William & Mary), Bernard Black (Northwestern University), Eric Luo (George Washington University), John Meurer (Medical College of Wisconsin), Paula Natalia Barreto Parra (Northwestern), Jeffrey Whittle (Medical College of Wisconsin), and Ruohao Zhang (Northwestern University).

Our research is supported by a grant from the National Institutes of Health.

A detailed discussion of our data sources and methods is available at  

Questions and suggestions for improvement: Please contact Professor Bernard Black at


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