Table 1

Table 1
Adjusted incidence rate ratios of SARS-CoV-2 reinfection, Italy, 24 August 2021–6 March 2022 (n =249,121)
		Reinfection (249,121)	PD (842,254,906)	Incidence per 100,000 PD	RR adjusted (95% CI)	p value
Epidemic phase^a	Delta	6,028	434,476,324	1.39	Reference
	Transition	36,509	124,883,250	29.23	8.79 (8.45–9.13)	< 0.001
	Omicron	206,584	282,895,332	73.02	18.09 (17.43–18.77)	< 0.001
Days from first diagnosis	90–210	25,126	147,300,836	17.06	Reference
	210–330	67,149	319,935,680	20.99	1.51 (1.47–1.56)	< 0.001
	330–450	121,934	284,817,183	42.81	1.73 (1.69–1.79)	< 0.001
	> 450	34,912	90,201,207	38.70	1.67 (1.62–1.72)	< 0.001
Vaccination status	Vaccinated with at least one dose for ≤ 120 days	81,235	408,702,801	19.88	Reference
	Vaccinated with at least one dose for > 120 days	77,829	216,463,056	35.95	1.53 (1.5–1.57)	< 0.001
	Unvaccinated	90,057	217,089,049	41.48	2.90 (2.83–2.97)	< 0.001
Sex	Male	112,804	410,792,861	27.46	Reference
Sex	Female	136,317	431,462,045	31.59	1.20 (1.18–1.22)	< 0.001
Age group (years)	0–19	51,212	129,028,476	39.69	1.03 (1.00–1.06)	0.0806
	20–39	82,037	211,577,554	38.77	1.22 (1.19–1.25)	< 0.001
	40–59	85,978	283,687,021	30.31	Reference
	60–79	21,268	160,343,346	13.26	0.47 (0.46–0.49)	< 0.001
	≥ 80	8,626	57,618,509	14.97	0.43 (0.41–0.45)	< 0.001
Nationality	Italian	227,273	767,676,929	29.61	Reference
Nationality	Foreign	21,848	74,577,977	29.30	0.60 (0.58–0.61)	< 0.001
Healthcare worker	No	236,178	815,250,169	28.97	Reference
Healthcare worker	Yes	12,943	27,004,737	47.93	1.90 (1.84–1.96)	< 0.001
CI: confidence interval; IRR: incidence rate ratios; PD: person-days; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2. ^a Epidemic phases: Delta: 24 Aug–5 Dec 2021; transition: 6 Dec 2021–2 Jan 2022; Omicron: 3 Jan–6 Mar 2022.