Clinical outcomes of the omicron variant compared with previous SARS-CoV-2 variants; meta-analysis of current reports

Table 1 Characteristics of included studies

First author	Country	Mean age		Immunization		Death rate		ICU admission		Length of stay		Ventilation		Number of cases		Ref.
		Omicron	Previous variants	Omicron	Previous variants	Omicron	Previous variants	Omicron	Previous variants	Omicron	Previous variants	Omicron	Previous variants	Omicron	Previous variants
Abdullah	South Africa	39	49.8	NA	NA	4.5%	21.3%	1%	4.3%	4	8.8	NA	NA	466	3962	[18]
Cloete	South Africa	4.2	NA	NA	NA	4	NA	7	NA	3.2	NA	7	NA	6287	NA	[19]
Christensen	USA	44.3	50.0	2497	101	38	170	NA	NA	3.2	5.1	49	144	4468	3149	[20]
Davies	South Africa	NA	NA	HR:0.41, 95%CI: 0.29-0.59		HR: 0.27, 95%CI: 0.19-0.38		NA	NA	NA	NA	NA	NA	5144	11609	[21]
Goga	South Africa	33	55	NA	NA	NA	NA	3%	16%	3	6	0.2%	8%	17650	22888	[22]
Lewnard	USA	NA	NA	6,981	784	1	12	4	20	5.5	15.8	0	11	52297	16982	[23]
Iuliano	USA	NA	NA	NA	NA	1854	1924	24776	24774	3	5	358	503	48238	25873	[24]
Maslo	South Africa	36	53	235	NA	27	520	180	1104	3	8	16	431	971	2628	[25]
Santos	Portugal	37.1	43.4	295	201	0	26	0	17	3.7	8.6	NA	NA	6581	9397	[26]
Torjesen	UK	NA	NA	NA	NA	NA	NA	9.9%	14%	1.7	6.6	2%	5.8%	NA	NA	[27]
Wang	USA	36.4	36.1	2.4%	3.1%	23	30	0.26%	0.78%	NA	NA	0.07%	0.43%	14054	563884	[28]
Wang	USA	1.49	1.73	NA	NA	NA	NA	0.14%	0.43%	NA	NA	0.33%	1.15%	7201	63203	[29]

ICU: Intensive care unit; NA: Not available; HR: Hazard ratio; CI: Confidence interval.