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As the number of people in the U.S. with coronavirus disease (COVID-19) continues to grow, there is increasing concern for adults who have a higher risk of developing serious illness if they are infected. The majority of people who become infected are expected to be asymptomatic or recover without needing special treatment, according to the World Health Organization. However, based on the most current information made available by the Centers for Disease Control and Prevention (CDC), older people and younger adults with serious medical conditions, such as heart disease, diabetes, lung disease, asthma and obesity have a greater risk of becoming severely ill if they get infected with coronavirus. CDC has issued specific guidance for people who fall into these categories.

To inform discussions about the challenges associated with coronavirus in the U.S., we first analyzed data from the 2018 Behavioral Risk Factor Surveillance System (BRFSS) to estimate the total number of adults nationwide, and by state, who have an elevated risk of serious illness if they are infected with coronavirus. CDC’s understanding of risk factors continues to evolve as the disease spreads, and more is learned about the effects of the coronavirus on different populations. We have therefore updated our previously published analysis to reflect a revised definition from the CDC of adults who are at higher risk of serious illness if they get infected with coronavirus. Our updated definition of high risk now includes: older adults (ages 65 or older, rather than 60 and older) and adults between the ages of 18 and 64 with heart disease, chronic obstructive pulmonary disease (COPD), uncontrolled asthma, diabetes, or a BMI greater than 40. To avoid overestimating the number and share of adults at higher risk of serious illness, our revised analysis does not include people with cancer; this is because BRFSS asks if respondents have ever had cancer, whereas CDC at-risk guidelines are limited to people who are currently immunocompromised, including cancer patients in treatment. We have also updated our weighting methodology to provide more robust state-level estimates of the number of adults at higher risk. See Methods for more information.

Key Findings

  • About four in ten adults (37.6%) ages 18 and older in the U.S. (92.6 million people) have a higher risk of developing serious illness if they become infected with coronavirus, due to their older age (65 and older) or health condition (Figure 1; Table 1).
  • Just over half of those at higher risk of developing a serious illness are ages 65 and older (55.2% or 51.1 million adults); however, the remaining 41.4 million adults ages 18-64 are at risk due to an underlying medical condition.
  • The share of adults ages 18 and older who have a higher risk of developing a more serious illness varies across the country, ranging from 49.3 percent (West Virginia) to 30 percent (Utah).
  • In some of the states with the highest number of reported coronavirus cases thus far, the share of adults at high risk of serious illness if infected is relatively high: Louisiana and Florida (at 42.1 percent, each) and Michigan (41.2 percent).
  • An estimated 5.1 million adults who are at higher risk of getting a serious illness if they become infected with coronavirus are uninsured.

Figure 1: Over 90 million of 246 million U.S. Adults are at Higher Risk of Serious Illness if Infected with Coronavirus

Discussion

The majority of people who become infected with coronavirus are not expected to become seriously ill, but a large segment of the U.S. adult population – one third (37.6 percent) of adults ages 18 and older – have a higher risk of serious illness if they do become infected due to their age or underlying medical condition. One group particularly at risk are the 1.3 million people living in nursing homes in the US. As the number of people who test positive for coronavirus continues to rise, and as more is learned about the progression of illness and treatment among those who become seriously ill, the current set of risk factors available to estimate the size of the at-risk population is likely to be refined. Given the paucity of data at this stage of the pandemic, and the high stakes involved for people who do get seriously ill, these estimates confirm the need to take unprecedented efforts to minimize the spread of the coronavirus.

Methods
This brief analyzes data from the nationally-representative, cross-sectional 2018 Behavioral Risk Factor Surveillance System (BRFSS) of adults ages 18 and older living in the community. BRFSS is an ongoing, state-based, random-digit-dialed telephone survey of non-institutionalized civilian adults. The 2018 survey has over 430,000 respondents. Information about the BRFSS is available at http://www.cdc.gov/brfss/index.html. For this updated analysis, we calculated the number of people at risk of serious illness if they get infected with coronavirus, using BRFSS, and we controlled these estimates to the 2018 American Community Survey (ACS) to generate population counts by state and age. Because of its large sample size, the ACS is generally seen as providing reliable population estimates by state. This updated analysis reflects this change in weighting methodology. The weighted total population is about 3% less in the ACS than in BRFFSS.

The estimate of the percentage of adults at higher risk utilizes the BRFSS survey weights to account for the complex sampling design. Data exclude adults living in Guam or Puerto Rico. Data represent adults who report ever being told by a doctor that they have one of the listed conditions. To avoid overestimating the number and share of adults at higher risk of serious illness, our revised analysis does not include people with cancer; this is because BRFSS asks if respondents have ever had cancer, whereas CDC at-risk guidelines are limited to people who are currently immunocompromised, including cancer patients in treatment. Because the CDC guidelines suggest that those with moderate or severe asthma are at greater risk than those with mild asthma, we adjusted the overall total to account for the share with uncontrolled asthma, adjusting the overall total by 62 percent, based on CDC prevalence. The change in estimates from our previous analysis are mainly attributable to the revised CDC at-risk guidelines.

Table 1: Number of U.S. Adults At Higher Risk Of Serious Illness If Infected With Coronavirus
Total, adults ages 18 and older   Adults under age 65.  Adults age 65 and older
State Total number, adults 18 and older Number at risk, adults 18 and older At-risk adults, as a share of all adults ages 18 and older Total number, adults under age 65 Number at risk due to health conditions, adults under age 65 Share of adults under age 65 at risk Total number, adults age
65 and older
Older adults, as a share of all at-risk adults
Overall 246,402,480 92,560,223 37.60% 195,281,293 41,439,036 21.20% 51,121,187 55.20%
Alaska 527,792 172,913 32.80% 442,335 87,456 19.80% 85,457 49.40%
Alabama 3,684,158 1,588,905 43.10% 2,873,170 777,917 27.10% 810,988 51.00%
Arkansas 2,231,289 971,477 43.50% 1,742,217 482,405 27.70% 489,072 50.30%
Arizona 5,389,431 2,107,495 39.10% 4,143,554 861,618 20.80% 1,245,877 59.10%
California 29,879,585 9,952,647 33.30% 24,302,948 4,376,010 18.00% 5,576,637 56.00%
Colorado 4,301,492 1,345,398 31.30% 3,506,700 550,606 15.70% 794,792 59.10%
Connecticut 2,739,381 985,861 36.00% 2,148,446 394,926 18.40% 590,935 59.90%
District Of Columbia 542,174 172,398 31.80% 459,618 89,842 19.50% 82,556 47.90%
Delaware 739,951 305,395 41.30% 562,058 127,502 22.70% 177,893 58.30%
Florida 16,683,102 7,018,513 42.10% 12,389,357 2,724,768 22.00% 4,293,745 61.20%
Georgia 7,748,091 2,803,400 36.20% 6,321,701 1,377,010 21.80% 1,426,390 50.90%
Hawaii 1,056,723 412,878 39.10% 798,667 154,822 19.40% 258,056 62.50%
Iowa 2,336,881 862,351 36.90% 1,819,010 344,480 18.90% 517,871 60.10%
Idaho 1,282,329 464,522 36.20% 1,006,426 188,619 18.70% 275,903 59.40%
Illinois 9,623,149 3,482,300 36.20% 7,697,443 1,556,594 20.20% 1,925,706 55.30%
Indiana 4,955,934 1,976,552 39.90% 3,940,531 961,149 24.40% 1,015,403 51.40%
Kansas 2,124,795 807,193 38.00% 1,683,235 365,633 21.70% 441,560 54.70%
Kentucky 3,341,735 1,455,749 43.60% 2,630,671 744,685 28.30% 711,064 48.80%
Louisiana 3,435,791 1,445,420 42.10% 2,736,213 745,842 27.30% 699,578 48.40%
Massachusetts 5,318,415 1,837,581 34.60% 4,215,360 734,526 17.40% 1,103,055 60.00%
Maryland 4,556,875 1,690,631 37.10% 3,650,537 784,293 21.50% 906,338 53.60%
Maine 1,060,936 451,409 42.50% 792,994 183,467 23.10% 267,942 59.40%
Michigan 7,649,977 3,152,031 41.20% 5,973,998 1,476,052 24.70% 1,675,979 53.20%
Minnesota 4,211,344 1,428,307 33.90% 3,354,163 571,126 17.00% 857,181 60.00%
Missouri 4,590,784 1,860,608 40.50% 3,590,211 860,035 24.00% 1,000,573 53.80%
Mississippi 2,185,597 929,387 42.50% 1,724,625 468,415 27.20% 460,972 49.60%
Montana 813,505 317,546 39.00% 615,520 119,561 19.40% 197,985 62.30%
North Carolina 7,785,717 3,038,856 39.00% 6,137,620 1,390,759 22.70% 1,648,097 54.20%
North Dakota 560,523 194,056 34.60% 450,954 84,487 18.70% 109,569 56.50%
Nebraska 1,404,355 514,118 36.60% 1,112,641 222,404 20.00% 291,714 56.70%
New Hampshire 1,059,120 428,938 40.50% 821,964 191,782 23.30% 237,156 55.30%
New Jersey 6,799,427 2,354,252 34.60% 5,396,351 951,176 17.60% 1,403,076 59.60%
New Mexico 1,575,314 619,893 39.40% 1,211,046 255,625 21.10% 364,268 58.80%
Nevada 2,307,514 833,620 36.10% 1,833,570 359,676 19.60% 473,944 56.90%
New York 15,028,787 5,550,169 36.90% 11,914,579 2,435,961 20.40% 3,114,208 56.10%
Ohio 8,817,672 3,506,796 39.80% 6,891,542 1,580,666 22.90% 1,926,130 54.90%
Oklahoma 2,879,096 1,175,713 40.80% 2,280,666 577,283 25.30% 598,430 50.90%
Oregon 3,257,427 1,297,341 39.80% 2,528,112 568,026 22.50% 729,315 56.20%
Pennsylvania 9,798,951 3,898,304 39.80% 7,547,656 1,647,009 21.80% 2,251,295 57.80%
Rhode Island 814,843 312,092 38.30% 639,889 137,138 21.40% 174,954 56.10%
South Carolina 3,838,837 1,590,048 41.40% 2,957,890 709,101 24.00% 880,947 55.40%
South Dakota 639,915 226,086 35.30% 500,965 87,136 17.40% 138,950 61.50%
Tennessee 5,105,824 2,121,941 41.60% 4,031,127 1,047,244 26.00% 1,074,697 50.60%
Texas 20,715,876 7,199,553 34.80% 17,205,161 3,688,838 21.40% 3,510,715 48.80%
Utah 2,189,374 657,278 30.00% 1,846,133 314,037 17.00% 343,241 52.20%
Virginia 6,343,962 2,275,390 35.90% 5,048,192 979,620 19.40% 1,295,770 56.90%
Vermont 490,326 191,781 39.10% 371,176 72,631 19.60% 119,150 62.10%
Washington 5,733,155 2,013,681 35.10% 4,590,384 870,910 19.00% 1,142,771 56.80%
Wisconsin 4,415,638 1,612,619 36.50% 3,459,881 656,862 19.00% 955,757 59.30%
West Virginia 1,397,752 689,770 49.30% 1,045,095 337,113 32.30% 352,657 51.10%
Wyoming 431,859 157,117 36.40% 336,991 62,249 18.50% 94,868 60.40%
NOTE: Data includes adults ages 18 and older; excludes adults living in nursing homes and other institutional settings.
SOURCE: KFF analysis of 2018 Behavioral Risk Factor Surveillance System.