Table 2.
Test Characteristics and Reported Exposures of Healthcare Personnel With Symptomatic SARS-CoV-2 Infection (Case-Participants) or Without SARS-CoV-2 Infection (Control-Participants) at 24 US Sites, October 2021–June 2022
| Characteristic | Participants With Characteristic/Total No. (%)a | SMD | |
|---|---|---|---|
| Case-Participants | Control-Participants | ||
| Variant period of SARS-CoV-2 testb | |||
| Delta | 620/3279 (18.9) | 834/3998 (20.9) | −0.049 |
| Omicron | 2659/3279 (81.1) | 3164/3998 (79.1) | 0.049 |
| Type of test | |||
| NAAT | 3116/3279 (95.0) | 3998/3998 (100.0) | −0.323 |
| Antigen test | 163/3279 (5.0) | 0/3998 (0) | 0.323 |
| Symptoms reportedc | |||
| No | 0/3279 (0) | 686/3998 (17.2) | −0.644 |
| Yes | 3279/3279 (100) | 3312/3998 (82.8) | 0.644 |
| Reason for SARS-CoV-2d | |||
| Symptoms | 2802/3279 (85.5) | 2827/3312 (85.4) | 0.003 |
| Exposure, no symptoms | 371/3279 (11.3) | 351/3312 (10.6) | 0.023 |
| Screening, no symptoms or known exposure | 35/3279 (1.1) | 59/3312 (1.8) | −0.060 |
| Other | 62/3279 (1.9) | 71/3312 (2.1) | −0.018 |
| Unknown or missing | 9/3279 (0.3) | 4/3312 (0.1) | 0.035 |
| If symptoms reported, fevere | |||
| No | 1496/3279 (45.6) | 3103/3998 (77.6) | −0.696 |
| Yes | 1783/3279 (54.4) | 895/3998 (22.4) | 0.696 |
| Any COVID-19 close contact ≤14 d before symptom onset or positive test resultf | 2286/3277 (69.8) | 2386/3997 (59.7) | 0.212 |
| At work, patient | 1013/2582 (39.2) | 1266/3253 (38.9) | −0.016 |
| At work, not a patient | 720/2270 (31.7) | 950/3055 (31.1) | −0.043 |
| Outside work | 1493/2934 (50.9) | 1244/3629 (34.3) | 0.300 |
| Level of anticipated direct patient contactg | |||
| Substantial | 931/3279 (28.4) | 1258/3998 (31.5) | −0.067 |
| Moderate | 241/3279 (7.3) | 272/3998 (6.8) | 0.021 |
| Minimal | 2079/3279 (63.4) | 2439/3998 (61.0) | 0.049 |
| Undefined | 28/3279 (0.9) | 29/3998 (0.7) | 0.015 |
| Exposures representing possible risk in the community | |||
| Close contact with an ill personf | 1369/3022 (45.3) | 1560/3678 (42.4) | 0.056 |
| Attended gathering with nonhousehold members | 1674/3258 (51.4) | 1835/3931 (46.7) | 0.103 |
| Public transport | 641/3268 (19.6) | 798/3978 (20.1) | −0.010 |
| Shared transport | 522/3271 (16.0) | 667/3976 (16.8) | −0.021 |
| Attended daycare or school | 1216/3098 (39.3) | 1635/3769 (43.4) | −0.082 |
| Household member in daycare | 203/3273 (6.2) | 340/3989 (8.5) | −0.089 |
Abbreviations: COVID-19, coronavirus disease 2019; NAAT, nucleic acid amplification test; SARS- CoV-2, severe acute respiratory syndrome coronavirus 2; SMD, standardized mean difference.
Case-participants had symptomatic SARS-CoV-2 infection confirmed by antigen test or NAAT; control-participants had a negative SARS-CoV-2 NAAT result, with or without symptoms.
The Delta-predominant period was defined as before 19 December 2021; the Omicron-predominant period, as 19 December 2021 or later.
Among 90 pregnant control-participants, 15 (16.7%) had no symptoms reported.
Among persons with symptoms reported during the 14 days after the test date; some participants had initially tested for other reasons listed.
Among symptomatic case-participants, 884 of 1904 booster dose recipients (46%) reported a fever, compared with 899 of 1375 (65%) of those who did not receive a booster; among symptomatic control-participants, these numbers were 671 of 3239 (21%) and 224 of 759 (30%), respectively.
Close contact was defined as being within 6 ft of another person for ≥15 minutes or having unprotected contact with body secretions or excretions.
The anticipated level of patient contact was categorized according to reported occupation using the same methods as a previous analysis [11]. Among 4487 participants anticipated to have substantial direct patient contact, 2263 (50.0%) were nurses and 947 (21.0%) were physicians.