Table 1.
Demographics and clinical characteristics of acute respiratory infection episodes (hospitalization, ED/UC visits, outpatient visits) with SARS-CoV-2 testing by COVID-19 case-control status
| Total (n = 113,174) | Test-positive COVID-19 cases (n = 20,523) | Test-negative controls (n = 92,651) | P value | |
|---|---|---|---|---|
| COVID vaccine status* | ||||
| ≥1 dose of BNT162b2 XBB vaccine | 7324 (6.5) | 1019 (5.0) | 6305 (6.8) | <0.001 |
| ≥1 dose of BA.4/5-adapted bivalent vaccine | 29,907 (26.4) | 5316 (25.9) | 24,591 (26.5) | 0.060 |
| ≥3 doses of original wild-type mRNA vaccine but no bivalent-adapted vaccines | 29,463 (26.0) | 5512 (26.9) | 23,951 (25.9) | 0.003 |
| ≥2 doses of original wild-type mRNA vaccine but no bivalent-adapted vaccines | 51,546 (45.6) | 9467 (46.1) | 42,079 (45.4) | 0.064 |
| No original wild-type mRNA or bivalent-adapted or non-mRNA vaccines | 24,747 (21.9) | 4454 (21.7) | 20,293 (21.9) | 0.530 |
| Time since last non-XBB adapted vaccine, median days (IQR) | 670 (413–820) | 679 (421–825) | 668 (412–819) | <0.001 |
| Age group | 0.002 | |||
| 18–64 years | 54,563 (48.2) | 10,099 (49.2) | 44,464 (48.0) | |
| 65–74 years | 27,821 (24.6) | 4820 (23.5) | 23,001 (24.8) | |
| ≥75 years | 30,790 (27.2) | 5604 (27.3) | 25,186 (27.2) | |
| Sex | 0.099 | |||
| Male | 98,172 (86.7) | 17,730 (86.4) | 80,442 (86.8) | |
| Female | 15,002 (13.3) | 2793 (13.6) | 12,209 (13.2) | |
| Body mass index category | <0.001 | |||
| Underweight ( < 18.5 kg/m2) | 1399 (1.2) | 183 (0.9) | 1216 (1.3) | |
| Healthy weight (18.5–24.9 kg/m2) | 34,083 (30.1) | 6223 (30.3) | 27,860 (30.1) | |
| Overweight (25–29.9 kg/m2) | 22,780 (20.2) | 4387 (21.4) | 18,393 (19.9) | |
| Obese ( ≥ 30 kg/m2) | 54,398 (48.3) | 9620 (46.9) | 44,778 (48.3) | |
| Missing | 514 (0.4) | 110 (0.5) | 404 (0.4) | |
| Region | <0.001 | |||
| Midwest | 22,167 (19.6) | 4599 (22.4) | 17,568 (19.0) | |
| Northeast | 15,063 (13.3) | 2940 (14.3) | 12,123 (13.1) | |
| West | 21,933 (19.4) | 3787 (18.5) | 18,146 (19.6) | |
| South | 54,011 (47.7) | 9197 (44.8) | 44,814 (48.4) | |
| Race | 0.397 | |||
| Black or African American | 29,699 (26.2) | 5364 (26.1) | 24,335 (26.3) | |
| White | 71,345 (63.0) | 12,905 (62.9) | 58,440 (63.1) | |
| Other race | 12,130 (10.7) | 2254 (11.0) | 9876 (10.7) | |
| Ethnicity | 0.831 | |||
| Hispanic or Latino | 10,527 (9.3) | 1917 (9.3) | 8610 (9.3) | |
| Not Hispanic or Latino | 102,647 (90.7) | 18,606 (90.7) | 84,041 (90.7) | |
| Smoking | <0.001 | |||
| Current or former | 58,062 (51.3) | 9987 (48.7) | 48,075 (51.9) | |
| Never | 36,570 (32.3) | 7106 (34.6) | 29,464 (31.8) | |
| Unknown | 18,542 (16.4) | 3430 (16.7) | 15,112 (16.3) | |
| Area deprivation index (ADI)** Quintile | 0.013 | |||
| 1 (Least Deprived) | 22,140 (19.6) | 4041 (19.7) | 18,099 (19.5) | |
| 2 | 22,134 (19.6) | 4127 (20.1) | 18,007 (19.4) | |
| 3 | 22,143 (19.6) | 4084 (19.9) | 18,059 (19.5) | |
| 4 | 22,126 (19.6) | 3981 (19.4) | 18,145 (19.6) | |
| 5 (Most Deprived) | 22,136 (19.6) | 3852 (18.8) | 18,284 (19.7) | |
| Unknown | 2495 (2.2) | 438 (2.1) | 2057 (2.2) | |
| VA Frailty index (VA-FI)*** | <0.001 | |||
| Non-frail (VA-FI ≤ 0.1) | 40,182 (35.5) | 7832 (38.2) | 32,350 (34.9) | |
| Pre-frail (VA-FI > 0.1-0.2) | 27,422 (24.2) | 5195 (25.3) | 22,227 (24.0) | |
| Mildly frail (VA-FI > 0.2-0.3) | 18,818 (16.6) | 3438 (16.8) | 15,380 (16.6) | |
| Moderately frail (VA-FI > 0.3-0.4) | 12,559 (11.1) | 1998 (9.7) | 10,561 (11.4) | |
| Severely frail (VA-FI ≥ 0.5) | 14,193 (12.5) | 2060 (10.0) | 12,133 (13.1) | |
| Healthcare exposures, 1 year prior | <0.001 | |||
| Hospital admission | 32,067 (28.3) | 4762 (23.2) | 27,305 (29.5) | |
| Nursing home admission | 3924 (3.5) | 947 (4.6) | 2977 (3.2) | <0.001 |
| Intensive care unit admission | 8825 (7.8) | 1172 (5.7) | 7653 (8.3) | <0.001 |
| Emergency department visit | 69,978 (61.8) | 11,733 (57.2) | 58,245 (62.9) | <0.001 |
| Primary care visit | 106,691 (94.3) | 19,349 (94.3) | 87,342 (94.3) | 0.957 |
| Charlson Comorbidity Index | <0.001 | |||
| 0 | 38,598 (34.1) | 7769 (37.9) | 30,829 (33.3) | |
| 1 | 21,698 (19.2) | 4057 (19.8) | 17,641 (19.0) | |
| 2 | 12,962 (11.5) | 2273 (11.1) | 10,689 (11.5) | |
| 3 | 10,833 (9.6) | 1912 (9.3) | 8921 (9.6) | |
| ≥ 4 | 29,083 (25.7) | 4512 (22.0) | 24,571 (26.5) | |
| Immunocompromised**** | 40,309 (35.6) | 5720 (27.9) | 34,589 (37.3) | <0.001 |
| Week of infection | <0.001 | |||
| Sep 25–Sep 30,2023 | 5503 (4.9) | 876 (4.3) | 4627 (5.0) | |
| Oct 01–Oct 07, 2023 | 4834 (4.3) | 731 (3.6) | 4103 (4.4) | |
| Oct 08–Oct 14, 2023 | 4358 (3.9) | 665 (3.2) | 3693 (4.0) | |
| Oct 15–Oct 21, 2023 | 4707 (4.2) | 779 (3.8) | 3928 (4.2) | |
| Oct 22–Oct 28, 2023 | 4624 (4.1) | 691 (3.4) | 3933 (4.2) | |
| Oct 29–Nov 04, 2023 | 4453 (3.9) | 663 (3.2) | 3790 (4.1) | |
| Nov 05–Nov 11, 2023 | 4741 (4.2) | 731 (3.6) | 4010 (4.3) | |
| Nov 12–Nov 18, 2023 | 5622 (5.0) | 972 (4.7) | 4650 (5.0) | |
| Nov 19–Nov 25, 2023 | 5155 (4.6) | 952 (4.6) | 4203 (4.5) | |
| Nov 26–Dec 02, 2023 | 6746 (6.0) | 1162 (5.7) | 5584 (6.0) | |
| Dec 03–Dec 09, 2023 | 6855 (6.1) | 1285 (6.3) | 5570 (6.0) | |
| Dec 10–Dec 16, 2023 | 6959 (6.1) | 1315 (6.4) | 5644 (6.1) | |
| Dec 17–Dec 23, 2023 | 8160 (7.2) | 1597 (7.8) | 6563 (7.1) | |
| Dec 24–Dec 30, 2023 | 8366 (7.4) | 1752 (8.5) | 6614 (7.1) | |
| Dec 31, 2023–Jan 06, 2024 | 8814 (7.8) | 1774 (8.6) | 7040 (7.6) | |
| Jan 07–Jan 13, 2024 | 7624 (6.7) | 1537 (7.5) | 6087 (6.6) | |
| Jan 14–Jan 20, 2024 | 5663 (5.0) | 1153 (5.6) | 4510 (4.9) | |
| Jan 21–Jan 27, 2024 | 6316 (5.6) | 1237 (6.0) | 5079 (5.5) | |
| Jan 28–Jan 31, 2024 | 3674 (3.2) | 651 (3.2) | 3023 (3.3) | |
| Prior COVID-19 infection**** | 31,195 (27.6) | 4878 (23.8) | 26,317 (28.4) | <0.001 |
| Virtual visit (outpatient only)***** | 2773 (10.3) | 1129 (23.9) | 1644 (7.4) | <0.001 |
| ICU admission (hospitalized only)****** | 4955 (20.5) | 624 (13.7) | 4331 (22.0) | <0.001 |
| Current influenza vaccine | 39,077 (34.5) | 7300 (35.6) | 31,777 (34.3) | <0.001 |
| Pneumococcal vaccine in last 5 years | 41,032 (36.3) | 7116 (34.7) | 33,916 (36.6) | <0.001 |
ARI acute respiratory infection, ED/UC emergency department/urgent care, VA Veterans Affairs.
Data are n (%) unless otherwise specified.
The data source did not indicate whether sex was self-reported or assigned.
All ARI encounters within a 30-day window were considered a single ARI episode. If multiple encounter types occurred during the 30-day window, the highest level of care was used (hospitalization > ED/UC > outpatient).
*The categories under “COVID vaccine status” were categorized as present or absent for each category.
**Area deprivation index (ADI) is a measure of socioeconomic disadvantage and was grouped into quintiles from least to most deprived neighborhoods (based on zip code)51.
***Frailty was defined using the ICD-10 updated Veterans Affairs Frailty Index (VA-FI) and categorized as non-frail (VA-FI ≤ 0.1), prefrail ( > 0.1–0.2), mildly frail ( > 0.2–0.3), moderately frail ( > 0.3–0.4), and severely frail ( > 0.4)52.
****Immunocompromised status was based on immunocompromising conditions in the year prior and immunosuppressive medications in the 90 days prior to the ARI episode based on a slightly modified algorithm that has been previously described49. Unlike the previously described algorithm, we used diagnosis codes to identify solid organ or hematopoietic stem cell transplantation and HIV/AIDs versus patient registries. Consistent with the previously described algorithm, we required one inpatient or two outpatient diagnosis code for an immunocompromising condition (leukemia, lymphoma, congenital immunodeficiencies, asplenia/hyposplenia, HIV/AIDS, and organ transplant) in the year prior and any immunosuppressive medication (alkylating agents, antibiotics, antimetbolites, antimitotics, monoclonal antibodies, other, immune-modulating agents, TNF Alpha antagonist, and steroids) with an outpatient days supply or inpatient administration in the 90 days prior.
****Prior COVID-19 infection was defined as any previous documented SARS-CoV-2 infection or no prior documented infection (yes or no).
*****Virtual visit was only assessed among those with an outpatient visit and defined as a virtual visit or not.
*****ICU admission was only assessed among those with a hospital admission and defined as admission to an ICU or not.