Between March 2021 and October 2022, a total of 21,139 patients met our inclusion criteria and were included the study. Upon propensity matching, 1,349 patients were included in the primary matched cohort (1,349 mAb-treated; 1,349 untreated). The propensity score matching diminished the imbalance in most of the key covariates, including age, race, immunosuppression, renal disorder, respiratory disorder, tobacco use, months into availability of mAb treatment, acuity level, and number of vaccinations. However, the propensity matched sample did differ significantly in months into mAb availability and number of COVID-19 vaccinations. Measures of association are available in Table 1.
Characteristics of the mAb patients in the primary cohort
In the propensity-matched cohort, mAb-treated patients reflected characteristics consistent with patients at a high risk for progression to severe COVID-19 (Table 1). Among patients who received mAb therapy (n = 1,349), 805 (60%) were aged 65 years or older, 387 (29%) were nonwhite, 136 (10%) were immunosuppressed, 275 (20%) suffered from renal disorders, and 452 (34%) suffered from respiratory disorders.
Table 1. Patient Characteristics and Covariate Balance Before and After Propensity Matching
| Treated, N = 1,349 |
Untreated, N = 19,790 |
p |
Treated, N = 1,349 |
Untreated, N = 1,349 |
p |
| Male |
636 (47%) |
8,273 (42%) |
<0.001 |
636 (47%) |
614 (46%) |
0.4 |
| Nonwhite |
387 (29%) |
7,743 (39%) |
<0.001 |
387 (29%) |
367 (27%) |
0.4 |
| Age 65+ |
805 (60%) |
7,286 (37%) |
<0.001 |
805 (60%) |
839 (62%) |
0.2 |
| Arrythmia |
305 (23%) |
3,150 (16%) |
<0.001 |
305 (23%) |
296 (22%) |
0.7 |
| Cancer |
186 (14%) |
1,801 (9.1%) |
<0.001 |
186 (14%) |
174 (13%) |
0.5 |
| Cardiovascular disease |
777 (58%) |
8,965 (45%) |
<0.001 |
777 (58%) |
744 (55%) |
0.2 |
| Diabetes |
250 (19%) |
2,814 (14%) |
<0.001 |
250 (19%) |
233 (17%) |
0.4 |
| Immunosuppressed |
136 (10%) |
603 (3.0%) |
<0.001 |
136 (10%) |
140 (10%) |
0.8 |
| Obese |
522 (39%) |
8,679 (44%) |
<0.001 |
522 (39%) |
537 (40%) |
0.6 |
| Renal disease |
275 (20%) |
2,460 (12%) |
<0.001 |
275 (20%) |
255 (19%) |
0.3 |
| Respiratory disease |
452 (34%) |
7,040 (36%) |
0.12 |
452 (34%) |
412 (31%) |
0.10 |
| Tobacco user |
47 (3.5%) |
2,206 (11%) |
<0.001 |
47 (3.5%) |
34 (2.5%) |
0.14 |
| Months since mAb approval |
15 (5) |
13 (5) |
<0.001 |
15 (5) |
14 (5) |
0.001 |
| Acuity level |
|
|
<0.001 |
|
|
0.13 |
| 1 |
5 (0.4%) |
179 (0.9%) |
|
5 (0.4%) |
14 (1.0%) |
|
| 2 |
173 (13%) |
3,168 (16%) |
|
173 (13%) |
156 (12%) |
|
| 3 |
923 (68%) |
11,756 (59%) |
|
923 (68%) |
916 (68%) |
|
| 4 |
248 (18%) |
4,687 (24%) |
|
248 (18%) |
263 (19%) |
|
| COVID vaccinations |
|
|
<0.001 |
|
|
0.040 |
| 0 |
1,298 (96%) |
18,256 (92%) |
|
1,298 (96%) |
1,299 (96%) |
|
| 1 |
14 (1.0%) |
420 (2.1%) |
|
14 (1.0%) |
19 (1.4%) |
|
| 2 |
4 (0.3%) |
408 (2.1%) |
|
4 (0.3%) |
8 (0.6%) |
|
| 3 |
9 (0.7%) |
489 (2.5%) |
|
9 (0.7%) |
14 (1.0%) |
|
| 4 |
24 (1.8%) |
217 (1.1%) |
|
24 (1.8%) |
9 (0.7%) |
|
Primary and secondary outcomes
The crude rates of rehospitalization, mortality, and inpatient outcomes are shown in Table 2. During the study period, the incidence of 28-day hospitalization in our primary matched cohort was 9.4% (n = 127/1,349) for untreated patients compared to 6.3% (n = 85/1,349) among mAb-treated patients. The mortality rate for untreated patients was 5.3% (n = 41/1,349) compared to 1.7% (n = 23/1,349) for mAb-treated patients. The rate of inpatient admission for untreated patients was 8.6% (n = 116/1,349) compared to 3.8% (n = 51/1,349) for mAb-treated patients. Rates of ICU and mechanical ventilation did not differ significantly by treatment group.
Table 2. Primary and Secondary Outcomes for Primary Matched Cohort
| Primary outcomes |
| 28-Day Readmission |
85 (6.3%) |
127 (9.4%) |
0.003 |
| Mortality |
23 (1.7%) |
71 (5.3%) |
<0.001 |
| Secondary outcomes |
| Any days as hospital inpatient |
51 (3.8%) |
116 (8.6%) |
<0.001 |
| Any days in ICU |
10 (0.7%) |
20 (1.5%) |
0.066 |
| Any days on ventilator |
4 (0.3%) |
4 (0.3%) |
>0.9 |
The adjusted analyses are presented in Table 3. Treatment with mAb was associated with reduced odds of 28-day rehospitalization (adjusted odds ratio [aOR] 0.66, [95% confidence interval (CI)] 0.49-0.87), P = 0.004). Mortality rates also differed significantly between the two groups. Treatment with mAb was associated with reduced odds of mortality (adjusted odds ratio [aOR] 0.32, [95% confidence interval (CI)] 0.19-0.51), P < 0.001). Treatment was also associated with reduced odds of inpatient admissions (adjusted odds ratio [aOR] 0.43, [95% confidence interval (CI)] 0.31-0.61), P < 0.001).
Table 3. Adjusted Odds Ratios
| OR |
95% CI |
p |
OR |
95% CI |
p |
OR |
95% CI |
p |
| Received mAb |
0.66 |
0.49, 0.87 |
0.004 |
0.32 |
0.19, 0.51 |
<0.001 |
0.43 |
0.31, 0.61 |
<0.001 |
| Months since mAb approval |
0.97 |
0.94, 1.00 |
0.038 |
0.96 |
0.92, 1.00 |
0.080 |
0.93 |
0.90, 0.96 |
<0.001 |
| COVID vaccinations |
1.16 |
0.90, 1.42 |
0.2 |
1.03 |
0.63, 1.44 |
>0.9 |
1.05 |
0.74, 1.37 |
0.8 |