Changes in the intrinsic severity of severe acute respiratory syndrome coronavirus 2 according to the emerging variant: a nationwide study from February 2020 to June 2022, including comparison with vaccinated populations

Ryu, Boyeong; Shin, Eunjeong; Kim, Dong Hwi; Lee, HyunJu; Choi, So Young; Kim, Seong-Sun; Kim, Il-Hwan; Kim, Eun-Jin; Lee, Sangwon; Jeon, Jaehyun; Kwon, Donghyok; Cho, Sungil

doi:10.1186/s12879-023-08869-7

Table 2 Case severity rate^a⁾ and case fatality rate^b⁾ by age group, period, and vaccination status (unit: %)

From: Changes in the intrinsic severity of severe acute respiratory syndrome coronavirus 2 according to the emerging variant: a nationwide study from February 2020 to June 2022, including comparison with vaccinated populations

Age group	Pre-vaccination		After-vaccination						Delta dominant vs Omicron dominant
	Pre-vaccination		Pre-delta dominant		Delta dominant		Omicron dominant		Delta dominant vs Omicron dominant
	Unvaccinated	Vaccinated	Unvaccinated	Vaccinated	Unvaccinated	Vaccinated	Unvaccinated	Vaccinated	Unvaccinated						Vaccinated
	Unvaccinated	Vaccinated	Unvaccinated	Vaccinated	Unvaccinated	Vaccinated	Unvaccinated	Vaccinated	Risk difference	Lower CI	Upper CI	Risk ratio	Lower CI	Upper CI	Risk difference	Lower CI	Upper CI	Risk ratio	Lower CI	Upper CI
Case Severity Rate (%)
Total (Crude)	3.82	-	2.06	3.56	2.66	1.75	0.26	0.11	-2.40	-2.46	-2.34	0.10	0.10	0.10	-1.64	-1.69	-1.59	0.06	0.06	0.07
Age stand-ardized	2.49	-	2.12	1.60	5.51	0.93	0.94	0.10	-4.57	-4.71	-4.42	0.17	0.14	0.21	-0.83	-0.86	-0.80	0.10	0.07	0.14
Age stand-ardized	(2.41—2.57)	-	(2.01—2.24)	(1.25—2.02)	(5.37—5.65)	(0.90—0.96)	(0.92—0.97)	(0.09—0.10)
0–9	0.00	-	0.00	-	0.02	0.00	0.00*	0.00	-0.01	-0.03	-0.00*	0.24	0.12	0.50	-	-	-	-	-	-
10–19	0.00	-	0.05	0.00	0.04	0.00	0.01	0.00^*	-0.04	-0.06	-0.02	0.14	0.08	0.23	0.00^*	0.00^*	0.00^*	-	-	-
20–29	0.09	-	0.19	0.00	0.30	0.03	0.05	0.00^*	-0.25	-0.30	-0.20	0.17	0.13	0.23	-0.02	-0.04	0.00*	0.12	0.05	0.25
30–39	0.33	-	0.42	0.33	1.09	0.09	0.07	0.00^*	-1.02	-1.12	-0.91	0.06	0.05	0.08	-0.08	-0.11	-0.05	0.05	0.03	0.07
40–49	0.69	-	1.03	0.58	2.22	0.16	0.19	0.01	-2.03	-2.19	-1.86	0.09	0.08	0.10	-0.15	-0.19	-0.11	0.06	0.05	0.08
50–59	1.79	-	2.12	1.14	5.36	0.46	0.71	0.04	-4.64	-4.94	-4.34	0.13	0.12	0.15	-0.43	-0.49	-0.36	0.08	0.07	0.10
60–69	5.46	-	4.71	4.59	14.68	1.95	2.03	0.12	-12.64	-13.37	-11.92	0.14	0.13	0.15	-1.83	-1.94	-1.72	0.06	0.06	0.07
70–79	15.33	-	10.94	8.49	31.42	5.44	6.09	0.45	-25.32	-26.82	-23.83	0.19	0.18	0.21	-4.99	-5.27	-4.71	0.08	0.08	0.09
≥ 80	27.69	-	20.54	8.70	44.28	12.58	10.52	1.81	-33.76	-35.45	-32.07	0.24	0.23	0.25	-10.77	-11.37	-10.17	0.14	0.14	0.15
Case Fatality Rate (%)
Total (Crude)	1.86	-	0.47	0.68	1.06	0.84	0.19	0.08	-0.87	-0.91	-0.83	0.18	0.17	0.18	-0.76	-0.79	-0.72	0.09	0.09	0.10
Age stand-ardized	1.17	-	0.60	0.31	2.49	0.46	0.63	0.07	-1.87	-1.97	-1.77	0.25	0.20	0.30	-0.39	-0.41	-0.37	0.15	0.10	0.20
Age stand-ardized	(1.12—1.23)		(0.54—0.67)	(0.17—0.53)	(2.40—2.59)	(0.44—0.48)	(0.61—0.64)	(0.07—0.07)
0–9	0.00	-	0.00	-	0.01	0.00	0.00^*	0.00	-0.01	-0.01	0.00^*	0.15	0.04	0.50	-	-	-	-	-	-
10–19	0.00	-	0.00	0.00	0.00	0.00	0.00^*	0.00	0.00^**	0.00^**	0.00^*	-	-	-	-	-	-	-	-	-
20–29	0.01	-	0.02	0.00	0.02	0.00^*	0.02	0.00^*	-0.00^*	-0.02	0.01	0.93	0.43	1.99	-0.00*	-0.01	0.00*	0.24	0.03	1.78
30–39	0.06	-	0.01	0.33	0.08	0.01	0.02	0.00^*	-0.06	-0.09	-0.03	0.22	0.14	0.36	-0.01	-0.02	0.00*	0.14	0.04	0.45
40–49	0.10	-	0.02	0.00	0.20	0.04	0.09	0.01	-0.12	-0.17	-0.06	0.42	0.31	0.58	-0.03	-0.05	-0.01	0.13	0.07	0.22
50–59	0.35	-	0.19	0.00	0.87	0.12	0.36	0.02	-0.51	-0.64	-0.38	0.41	0.34	0.50	-0.10	-0.13	-0.07	0.17	0.12	0.22
60–69	1.39	-	0.69	0.54	4.97	0.57	1.08	0.07	-3.89	-4.34	-3.45	0.22	0.19	0.24	-0.50	-0.56	-0.44	0.12	0.10	0.13
70–79	7.02	-	3.01	1.89	17.07	2.45	4.13	0.30	-12.94	-14.15	-11.73	0.24	0.22	0.26	-2.15	-2.34	-1.96	0.12	0.11	0.13
≥ 80	21.36	-	12.16	2.72	34.72	8.84	8.75	1.47	-25.97	-27.59	-24.36	0.25	0.24	0.27	-7.37	-7.89	-6.86	0.17	0.16	0.18

CI confidence intervals
^*< 0.01, ^**< 0.001
^aCase severity rate: (number of severe/critical cases and deaths among confirmed cases in a specific period)/number of confirmed cases in a specific period * 100 (standard population: total number of confirmed cases in the whole period)
^bCase fatality rate: (number of deaths among confirmed cases in a specific period)/number of confirmed cases in a specific period * 100 (standard population: total number of confirmed cases in the whole period)

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ISSN: 1471-2334

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