TABLE 1. Characteristics of emergency department and urgent care encounters among children aged 5–17 years with COVID-19–like illness,* by COVID-19 Pfizer-BioNTech vaccination status^† and SARS-CoV-2 test result — 10 states,^§ April 2021–January 2022.

Characteristic	Total no. (column %)	No. (row %)				SMD¶	No. (row %)	SMD¶
		Pfizer-BioNTech vaccination status					Positive SARS-CoV-2 test result
		Unvaccinated	2 doses (14–149 days earlier)	2 doses (≥150 days earlier)	3 doses (≥7 days earlier)
All ED and UC encounters	39,217	28,084 (71.6)	7,821 (19.9)	3,238 (8.3)	74 (0.2)	—	9,252 (23.6)	—
Variant predominance period**
Pre-Delta	955 (2.4)	851 (89.1)	104 (10.9)	0 (—)	0 (—)	0.84	113 (11.8)	0.81
B.1.617.2 (Delta)	26,048 (66.4)	17,596 (67.6)	6,496 (24.9)	1,954 (7.5)	2 (0.0)		3,655 (14.0)
B.1.1.529 (Omicron)	12,214 (31.1)	9,637 (78.9)	1,221 (10.0)	1,284 (10.5)	72 (0.6)		5,484 (44.9)
Site
Baylor Scott & White Health	4,408 (11.2)	3,932 (89.2)	313 (7.1)	163 (3.7)	0 (—)	0.83	1,653 (37.5)	0.48
Columbia University	1,564 (3.9)	1,260 (80.6)	226 (14.5)	77 (4.9)	1 (0.1)		510 (32.6)
HealthPartners	2,089 (5.3)	988 (47.3)	844 (40.4)	257 (12.3)	0 (—)		231 (11.1)
Intermountain Healthcare	12,993 (33.1)	8,314 (64.0)	3,274 (25.2)	1,372 (10.6)	33 (0.3)		2,002 (15.4)
Kaiser Permanente Northern California	2,287 (5.8)	1,134 (49.6)	795 (34.8)	339 (14.8)	19 (0.8)		578 (25.3)
Kaiser Permanente Northwest	1,508 (3.8)	841 (55.8)	447 (29.6)	212 (14.1)	8 (0.5)		354 (23.5)
Regenstrief Institute	7,374 (18.8)	6,008 (81.5)	972 (13.2)	384 (5.2)	10 (0.1)		2,391 (32.4)
University of Colorado	6,994 (17.8)	5,607 (80.2)	950 (13.6)	434 (6.2)	3 (0.0)		1,533 (21.9)
Age group, yrs
5–11	9,181 (23.4)	8,599 (93.7)	582 (6.3)	0 (—)	0 (—)	1.07	2,776 (30.2)	0.20
12–15	18,138 (46.2)	12,064 (66.5)	4,547 (25.1)	1,517 (8.4)	10 (0.1)		3,873 (21.4)
16–17	11,898 (30.3)	7,421 (62.4)	2,692 (22.6)	1,721 (14.5)	64 (0.5)		2,603 (21.9)
Sex
Male††	18,907 (48.2)	13,658 (72.2)	3,713 (19.6)	1,505 (8.0)	31 (0.2)	0.07	4,369 (23.1)	0.03
Female	20,310 (51.7)	14,426 (71.0)	4,108 (20.2)	1,733 (8.5)	43 (0.2)		4,883 (24.0)
Race/Ethnicity
Hispanic	9,316 (23.7)	7,069 (75.9)	1,662 (17.8)	571 (6.1)	14 (0.2)	0.36	2,458 (26.4)	0.29
White, non-Hispanic	20,177 (51.4)	13,934 (69.1)	4,295 (21.3)	1,913 (9.5)	35 (0.2)		3,888 (19.3)
Black, non-Hispanic	4,106 (10.4)	3,405 (82.9)	503 (12.3)	195 (4.7)	3 (0.1)		1,504 (36.6)
Other, non-Hispanic§§	2,987 (7.6)	1,876 (62.8)	779 (26.1)	318 (10.6)	14 (0.5)		718 (24.0)
Unknown	2,631 (6.7)	1,800 (68.4)	582 (22.1)	241 (9.2)	8 (0.3)		684 (26.0)
Chronic respiratory condition ¶¶
Yes††	3,183 (8.1)	2,160 (67.9)	728 (22.9)	284 (8.9)	11 (0.3)	0.11	456 (14.3)	0.17
No	36,034 (91.8)	25,924 (71.9)	7,093 (19.7)	2,954 (8.2)	63 (0.2)		8,796 (24.4)
Chronic nonrespiratory condition***
Yes††	1,815 (4.6)	1,260 (69.4)	372 (20.5)	178 (9.8)	5 (0.3)	0.05	379 (20.9)	0.03
No	37,402 (95.3)	26,824 (71.7)	7,449 (19.9)	3,060 (8.2)	69 (0.2)		8,873 (23.7)

Abbreviations: ED = emergency department; ICD-9 = International Classification of Diseases, Ninth Revision; ICD-10 = International Classification of Diseases, Tenth Revision; SMD = standardized mean or proportion difference; UC = urgent care.

* Medical events with an encounter or discharge code consistent with COVID-19–like illness were included, using ICD-9 and ICD-10. Four categories of codes were considered: 1) acute respiratory illness, including COVID-19, respiratory failure, viral or bacterial pneumonia, asthma exacerbation, influenza, and viral illness not otherwise specified; 2) nonrespiratory COVID-19–like illness diagnoses including cause-unspecified gastroenteritis, thrombosis, and acute myocarditis; 3) respiratory signs and symptoms consistent with COVID-19–like illness, including hemoptysis, cough, dyspnea, painful respiration, or hypoxemia; and 4) signs and symptoms of acute febrile illness. One code in any of the four categories was sufficient for inclusion. Clinician-ordered molecular assays (e.g., real-time reverse transcription–polymerase chain reaction) for SARS-CoV-2 occurring ≤14 days before to <72 hours after the encounter date were included.

^† Vaccination was defined as having received the listed number of doses of COVID-19 Pfizer-BioNTech BNT162b2 vaccine ≥14 days (for 2 doses) or ≥7 days (for 3 doses) before the medical event index date, which was the date of respiratory specimen collection associated with the most recent positive or negative SARS-CoV-2 test result before medical event or the admission date if testing only occurred after the admission.

^§ Partners contributing data on medical events were in California (vaccine availability: April 30, 2021), Colorado (May 22, 2021), Indiana (April 27, 2021), Minnesota and Wisconsin (April 21, 2021), New York (April 27, 2021), Oregon and Washington (April 28, 2021), Texas (March 29, 2021), Utah (April 9, 2021). The study period began in September 2021 for partners located in Texas. For adolescents aged 16–17 years, the study period began when COVID-19 vaccines became available to all persons aged ≥16 years at each study site. For children aged 5–11 and persons aged 12–15 years, the study period began 5 weeks after the Pfizer-BioNTech vaccine was authorized for each age group (November 2, 2021, and May 12, 2021, respectively).

^¶ An absolute SMD ≥0.20 indicates a nonnegligible difference in variable distributions between medical events for vaccinated versus unvaccinated patients; single SMD calculated by averaging pairwise comparisons of each vaccinated category versus unvaccinated and separately for patients with SARS-CoV-2–positive versus SARS-CoV-2–negative test results. For example, the age SMD calculation comparing unvaccinated versus different vaccinated categories was generated by averaging the pairwise SMD calculations for unvaccinated and 2 doses (14–149 days earlier), unvaccinated and 2 doses (≥150 days earlier), and unvaccinated and 3 doses (≥7 days earlier). In addition, the age SMD calculation comparing negative SARS-CoV-2 test result and positive SARS-CoV-2 test result was generated by directly calculating the SMD for negative SARS-CoV-2 test result and positive SARS-CoV-2 test result.

** Estimated date of Delta and Omicron predominance at contributing sites: California (Delta: June 23, 2021; Omicron: December 21, 2021); Colorado (Delta: June 3, 2021; Omicron: December 19, 2021); Indiana (Delta: June 23, 2021; Omicron: December 26, 2021); Minnesota and Wisconsin (Delta: June 28, 2021; Omicron: December 25, 2021); New York (Delta: June 30, 2021; Omicron: December 18, 2021); Oregon and Washington (Delta: June 30, 2021; Omicron: December 24, 2021); Texas (Delta: July 3, 2021; Omicron: December 16, 2021); Utah (Delta: June 1, 2021; Omicron December 24, 2021). Pre-Delta refers to the period before Delta predominance.

^†† Indicates the reference group used for standardized mean or proportion difference calculations for dichotomous variables.

^§§ Other race includes Asian, Native Hawaiian or other Pacific islander, American Indian or Alaska Native, Other not listed, and multiple races.

^¶¶ Chronic respiratory condition was defined as the presence of discharge code for asthma, sleep apnea, or other lung disease using ICD-9 and ICD-10 diagnosis codes.

*** Chronic nonrespiratory condition was defined as the presence of discharge code for heart failure, ischemic heart disease, hypertension, other heart disease, stroke, other cerebrovascular disease, diabetes type I or II, other diabetes, metabolic disease, clinical obesity, clinically underweight, renal disease, liver disease, blood disorder, immunosuppression, organ transplant, cancer, neurologic disorder, musculoskeletal disorder, Down Syndrome, congenital heart disease, neurologic conditions, muscular dystrophy, sickle cell disease, prematurity (<24 weeks), developmental delay, technology dependence, or chronic gastrointestinal disease/irritable bowel syndrome.