Severity of SARS-CoV-2 Omicron BA.2 infection in unvaccinated hospitalized children: comparison to influenza and parainfluenza infections

Figures & data

Table 1 . Clinical characteristics of all hospital admissions between Omicron BA.2 and influenza and parainfluenza viral infections.

	SARS-CoV-2: Omicron BA.2 (n = 1144)	Influenza (n = 32212)	p-value^+ (Omicron vs Influenza)	Parainfluenza (n = 16423)	p-value^+(Omicron vs Parainfluenza)
Data period, day/month/year	05/02/2022–28/02/2022	01/01/2015–31/12/2019		01/01/2015–31/12/2019
Sex
Male	658 (57.5%)	17504 (54.3%)	0.04*	9228 (56.2%)	0.39
Female	486 (42.9%)	14708 (45.7%)		7159 (43.8%)
Age mean in years (SD)	3.4 (3.1)	4.1 (2.8)	<0.001***	2.6 (2.1)	<0.001***
0–5 years old	918 (80.2%)	24334 (75.5%)		15268 (93.0%)
6–11 years old	226 (19.8%)	7878 (24.5%)		1155 (7.0%)
Comorbidities	71 (6.2%)	1592 (4.9%)	0.06	1393 (8.5%)	0.008**
Mortality and severe complications
Death cases	2 (0.2%)^‡	16 (0.1%)		7 (0.04%)
PICU admissions	21 (1.8%)	254 (0.8%)		270 (1.6%)
Mechanical ventilation	8 (0.7%)	82 (0.3%)		106 (0.7%)
Oxygen use	11 (1.0%)	120 (0.4%)		225 (1.4%)
Neurological complications	171 (15.0%)	2707 (8.4%)		1258 (7.7%)
All seizures	166 (14.5%)	2650 (8.2%)		1248 (7.6%)
Febrile seizures	133 (11.6%)	2303 (7.2%)		1142 (7.0%)
Seizures with fever	28 (2.5%)	290 (1.0%)		42 (0.3%)
Breakthrough seizures with epilepsy	5 (0.4%)	57 (0.2%)		64 (0.4%)
Encephalitis/encephalopathy	5 (0.4%)	78 (0.2%)		17 (0.1%)
Respiratory complications	70 (6.1%)	2343 (7.3%)		2891 (17.6%)
Croup	61 (5.3%)	601 (1.9%)		889 (5.4%)
Pneumonia	10 (0.9%)	1756 (5.5%)		2030 (12.4%)
Croup/pneumonia ratio	6.10	0.34		0.44

Data are n (%) unless otherwise specified. PICU = paediatric intensive care units.

*p < 0.05,

**p < 0.01,

***p < 0.001.

⁺ Fisher's Exact test was used when comparing binary variables, independent t-test was used when comparing two continuous variables.

^‡ Two deaths were extracted from CDARS. During this study period, 4 total deaths were recorded by the Centre for Health Protection, Hong Kong, since these 2 deaths occurred in the Accident & Emergency Department and therefore were not inputted into CDARS by the admitted in-patient wards.

Table 2 . Relative risks of complications for Omicron BA.2 in comparison to influenza and parainfluenza viral infections.

	SARS-CoV-2 Omicron BA.2 vs Influenza				SARS-CoV-2 Omicron BA.2 vs Parainfluenza
	Crude		Adjusted^+		Crude		Adjusted^+
	RR (95% CI)	p-value	RR (95% CI)	p-value	RR (95% CI)	p-value	RR (95% CI)	p-value
Severe complications
Death cases	3.5 (0.8–15.3)	0.09	2.7 (0.5–15.7)	0.26	4.1 (0.9–19.7)	0.08	4.7 (1.1–19.6)	0.04*
PICU admissions	2.3 (1.5–3.6)	<0.001***	2.1 (1.3–3.3)	0.001**	1.1 (0.7–1.7)	0.62	1.2 (0.8–1.9)	0.37
Mechanical ventilation	2.7 (1.3–5.7)	0.006**	2.3 (1.1–4.9)	0.03*	1.1 (0.5–2.2)	0.83	1.3 (0.6–2.6)	0.55
Oxygen use	2.6 (1.4–4.8)	0.003**	2.3 (1.2–4.2)	0.009**	0.7 (0.4–1.3)	0.25	0.8 (0.4–1.4)	0.40
Neurological complications	1.8 (1.5–2.1)	<0.001***	1.6 (1.4–1.9)	<0.001***	2.0 (1.7–2.3)	<0.001***	1.9 (1.6–2.2)	<0.001***
All seizures	1.8 (1.5–2.0)	<0.001***	1.6 (1.4–1.9)	<0.001***	1.9 (1.6–2.2)	<0.001***	1.9 (1.6–2.2)	<0.001***
Febrile seizures	1.6 (1.4–1.9)	<0.001***	1.4 (1.2–1.6)	<0.001***	1.7 (1.4–2.0)	<0.001***	1.7 (1.4–2.0)	<0.001***
Seizures with fever	2.7 (1.8–4.0)	<0.001***	3.0 (2.1–4.2)	<0.001***	9.6 (5.9–15.4)	<0.001***	4.3 (2.4–7.6)	<0.001***
Breakthrough seizures with epilepsy	2.5 (1–6.2.0)	0.05	NA	NA	1.1 (0.5–2.8)	0.81	NA	NA
Encephalitis/ encephalopathy	1.8 (0.7–4.5)	0.20	1.8 (0.8–4.2)	0.17	4.2 (1.6–11.4)	0.005**	5.3 (1.6–17.9)	0.007**
Respiratory complications	0.8 (0.7–1.1)	0.14	0.8 (0.7–1.0)	0.09	0.3 (0.3–0.4)	<0.001***	0.3 (0.3–0.4)	<0.001***
Croup	2.9 (2.2–3.7)	<0.001***	2.0 (1.5–2.6)	<0.001***	1.0 (0.8–1.3)	0.91	1.0 (0.8–1.3)	0.74
Pneumonia	0.2 (0.1–0.3)	<0.001***	0.2 (0.1–0.3)	<0.001***	0.1 (0.03–0.1)	<0.001***	0.1 (0.03–0.1)	<0.001***

RR = relative risk, CI = confidence interval.

⁺ Model was adjusted by age, sex and comorbidities.

*p < 0.05,

**p < 0.01,

***p < 0.001.

NA = not applicable as epilepsy is a co-morbid condition