TABLE 1. Characteristics of hospitalized adults with previous SARS-CoV-2 infection,* by subsequent nucleic acid amplification test result†— United States, June 2021–February 2022§.
| Characteristic | No. (column %) |
p-value** | ||
|---|---|---|---|---|
| Total (N = 11,283) | Case-patients (NAAT-positive)¶ (n = 3,761) | Control-patients (NAAT-negative)¶ (n = 7,522) | ||
|
Age group, yrs
| ||||
| 18–29 |
993 (8.8) |
331 (8.8) |
662 (8.8) |
>0.990 |
| 30–44 |
1,717 (15.2) |
573 (15.2) |
1,144 (15.2) |
|
| 45–64 |
3,804 (33.7) |
1,273 (33.8) |
2,531 (33.6) |
|
| ≥65 |
4,769 (42.3) |
1,584 (42.1) |
3,185 (42.3) |
|
|
Sex
| ||||
| Women |
6,391 (56.6) |
2,114 (56.2) |
4,277 (56.9) |
0.510 |
| Men |
4,892 (43.4) |
1,647 (43.8) |
3,245 (43.1) |
|
|
Race and ethnicity
| ||||
| White, non-Hispanic |
6,963 (61.7) |
2,286 (60.8) |
4,677 (62.2) |
0.026 |
| Black, non-Hispanic |
2,821 (25.0) |
924 (24.6) |
1,897 (25.2) |
|
| Hispanic |
1,131 (10.0) |
413 (11.0) |
718 (9.5) |
|
| Other, non-Hispanic†† |
368 (3.3) |
138 (3.7) |
230 (3.1) |
|
|
Underlying health conditions§§
| ||||
| 0 |
536 (4.8) |
198 (5.3) |
338 (4.5) |
<0.001 |
| 1 |
1,610 (14.3) |
641 (17.0) |
969 (12.9) |
|
| >1 |
9,137 (81.0) |
2,922 (77.7) |
6,215 (82.6) |
|
|
Vaccination status
¶¶
| ||||
| Unvaccinated |
5,874 (52.1) |
2,303 (61.2) |
3,571 (47.5) |
<0.001 |
| Any mRNA vaccine, 1 dose |
574 (5.1) |
161 (4.3) |
413 (5.5) |
|
| Any mRNA vaccine, 2 doses |
3,534 (31.3) |
1,038 (27.6) |
2,496 (33.2) |
|
| Any mRNA vaccine, booster dose |
1,301 (11.5) |
259 (6.9) |
1,042 (13.9) |
|
|
Clinical encounters during 2019
| ||||
| 0 |
2,403 (21.3) |
781 (20.8) |
1,622 (21.6) |
<0.001 |
| 1–9 |
4,199 (37.2) |
1,628 (43.3) |
2,571 (34.2) |
|
| ≥10 |
4,681 (41.5) |
1,352 (35.9) |
3,329 (44.3) |
|
|
Month of hospital admission
| ||||
| Jun 2021 |
156 (1.4) |
54 (1.4) |
102 (1.4) |
0.930 |
| Jul 2021 |
528 (4.7) |
179 (4.8) |
349 (4.6) |
|
| Aug 2021 |
982 (8.7) |
320 (8.5) |
662 (8.8) |
|
| Sep 2021 |
874 (7.7) |
294 (7.8) |
580 (7.7) |
|
| Oct 2021 |
621 (5.5) |
204 (5.4) |
417 (5.5) |
|
| Nov 2021 |
583 (5.2) |
198 (5.3) |
385 (5.1) |
|
| Dec 2021 |
1,875 (16.6) |
601 (16.0) |
1,274 (16.9) |
|
| Jan 2022 |
4,555 (40.4) |
1,548 (41.2) |
3,007 (40.0) |
|
| Feb 2022 |
1,109 (9.8) |
363 (9.7) |
746 (9.9) |
|
|
Hospitalization variant predominance period***
| ||||
| B.1.617.2 (Delta) |
4,385 (38.9) |
1,437 (38.2) |
2,948 (39.2) |
0.310 |
| B.1.1.529 (Omicron) |
6,898 (61.1) |
2,324 (61.8) |
4,574 (60.8) |
|
|
U.S. Census region
| ||||
| Northeast |
2,340 (20.7) |
780 (20.7) |
1,560 (20.7) |
|
| Midwest |
3,300 (29.2) |
1,100 (29.2) |
2,200 (29.2) |
>0.990 |
| South |
5,133 (45.5) |
1,711 (45.5) |
3,422 (45.5) |
|
| West |
510 (4.5) |
170 (4.5) |
340 (4.5) |
|
|
Initial infection variant predominance period***
| ||||
| Pre-Delta* |
9,593 (85.0) |
3,226 (85.8) |
6,367 (84.6) |
0.110 |
| B.1.617.2 (Delta)5 |
1,690 (15.0) |
535 (14.2) |
1,155 (15.4) |
|
|
Initial diagnosis source*
| ||||
| COVID-19 diagnosis |
4,250 (37.7) |
1,615 (42.9) |
2,635 (35.0) |
<0.001 |
| NAAT result |
1,013 (9.0) |
317 (8.4) |
696 (9.3) |
|
| Both |
6,020 (53.4) |
1,829 (48.6) |
4,191 (55.7) |
|
|
Initial infection to NAAT associated with hospitalization, days†
| ||||
| 90–119 |
735 (6.5) |
287 (7.6) |
448 (6.0) |
<0.001 |
| 120–179 |
1,389 (12.3) |
479 (12.7) |
910 (12.1) |
|
| 180–269 |
1,787 (15.8) |
552 (14.7) |
1,235 (16.4) |
|
| 270–364 |
2,402 (21.3) |
711 (18.9) |
1,691 (22.5) |
|
| ≥365 | 4,970 (44.0) | 1,732 (46.1) | 3,238 (43.0) | |
Abbreviation: NAAT = nucleic acid amplification test.
* Initial diagnosis was based on a previous positive SARS-CoV-2 NAAT or clinical diagnosis of COVID-19 >90 days before the date of the NAAT associated with subsequent hospitalization. COVID-19 was defined as a clinical encounter with any of the following International Classification of Diseases, Tenth Revision diagnostic codes: U07.1, J12.81, or J12.82.
† Defined as NAAT performed between 10 days before and 3 days after the date of hospital admission with a diagnosis of COVID-19-like illness. COVID-19–like illness diagnoses were defined based on others’ methods (https://www.nejm.org/doi/full/10.1056/nejmoa2110362, Supplement Table S2) and included acute respiratory illness (e.g., COVID-19, respiratory failure, or pneumonia) or related signs or symptoms (e.g., cough, fever, dyspnea, vomiting, or diarrhea) using diagnostic codes from the International Classification of Diseases, Tenth Revision.
§ Patients were eligible for inclusion if the hospitalization-associated SARS-CoV-2 NAAT was performed during June 20, 2021–February 24, 2022.
¶ Cases had a positive SARS-CoV-2 NAAT result associated with hospitalization; controls had a negative SARS-CoV-2 NAAT result associated with hospitalization.
** Wilcoxon rank-sum tests and chi-square tests were used to compare medians and proportions, respectively; p-values <0.05 were considered statistically significant.
†† Other non-Hispanic includes Asian, Native Hawaiian or other Pacific Islander, and American Indian or Alaska Native persons.
§§ Underlying conditions were extracted from electronic health record clinical encounter data and were based on a CDC list of conditions associated with the highest risk for COVID-19 (https://www.cdc.gov/coronavirus/2019-ncov/hcp/clinical-care/underlyingconditions.html, accessed March 23, 2022), and included the following: alcoholic liver disease, autoimmune hepatitis, bronchiectasis, bronchopulmonary dysplasia, cancer, cardiomyopathy, cerebrovascular disease, chronic kidney disease, cirrhosis, chronic obstructive pulmonary disease, coronary artery disease, current smoker, administration or prescription of nontopical glucocorticoids within the previous 12 months, heart failure, HIV, immune deficiency, administration or prescription of immunosuppressive medications within the previous 12 months, interstitial lung disease, nonalcoholic fatty liver disease, obesity, pulmonary arterial hypertension, pulmonary embolus, pregnancy, solid organ transplant, tuberculosis, and type 1 or 2 diabetes. Among these, diagnoses associated with immunocompromise had overall similar prevalence between cases and controls, including immunosuppressive medications other than steroids (7.9% of case-patients and 7.3% of control-patients), immune deficiencies (4.4% of case-patients and 4.5% of control-patients), solid organ transplant recipients (2.4% of case-patients and 1.8% of control-patients) and HIV (0.9% of case-patients and 0.9% of control-patients).
¶¶ Patients were categorized on the date of NAAT associated with hospitalization as unvaccinated if no COVID-19 vaccine had been received; after dose 1 if ≥14 days had elapsed since receipt of the first dose of an mRNA COVID-19 vaccine and before any second dose; after dose 2 if ≥14 days had elapsed since receipt of the second dose of an mRNA COVID-19 vaccine, and no subsequent dose was received; and after a booster dose if ≥14 days had elapsed since receipt of an mRNA booster dose administered ≥5 months after a second dose. Patients were excluded from the analysis if they received a non-mRNA COVID-19 vaccine; the day of the NAAT-associated hospitalization was <14 days after dose 1, dose 2, or a booster dose; dose 2 was received <14 days after dose 1; any booster dose was <5 months after dose 2, they received >3 doses of vaccine, or their previous positive NAAT result or COVID-19 diagnosis was after date of the most recent vaccine dose. Median time from receipt of dose 1 to dose 2 was 21 days (IQR = 21–24) for Pfizer-BioNTech and 28 days (IQR = 28–30) for Moderna vaccines. Median time from receipt of dose 2 to dose 3 was 232 days (IQR = 203–258) for Pfizer-BioNTech and 236 days (IQR = 210–261) for Moderna vaccines.
*** Periods were defined as a range of dates when estimated national prevalence of a SARS-CoV-2 variant exceeded 50% as pre-Delta (before June 20, 2021), Delta (during June 20, 2021–December 18, 2021), and Omicron (from December 19, 2021). https://covid.cdc.gov/covid-data-tracker/#variant-proportions