Is a tiered restrictions system an effective intervention for COVID-19 control? Results from Portugal, November-December 2020

Table 2 COVID-19 incidence trends after the tiered restriction system implementation, by tier, considering different time periods

Parameters	Model 1 (T1-T2)		Model 2 (T2-T3)		Model 3 (T1-T3)
Parameters	Estimate	95% CI	Estimate	95% CI	Estimate	95% CI
IR in Moderate tier in the first moment*	56.92	[45.12; 71.81]	41.03	[27.93; 60.27]	63.94	[53.76; 76.05]
IRR High tier vs. moderate tier	2.66	[1.96; 3.63]	3.44	[2.03; 5.85]	2.38	[1.91; 2.98]
IRR Very high tier vs. moderate tier	8.29	[6.20; 10.90]	6.98	[4.31; 11.31]	5.82	[4.71; 7.18]
GR Moderate tier	1.18	[1.07; 1.30]	1.23	[1.12; 1.34]	1.15	[1.10; 1.20]
GR in High tier	1.06	[0.98; 1.15]	1.08	[1.00; 1.17]	1.06	[1.02; 1.10]
GR in Very high tier	0.81	[0.76; 0.86]	0.97	[0.91; 1.04]	0.89	[0.87; 0.92]
GRR High tier vs. moderate tier	0.90	[0.79; 1.02]	0.88	[0.78; 1.00]	0.92	[0.87; 0.98]
GRR Very high tier vs. moderate tier	0.68	[0.61; 0.77]	0.79	[0.71; 0.88]	0.77	[0.74; 0.82]

Note: CI– confidence interval; GR– Growth rate; GRR– Growth rate ratio; IR– Incidence rate per 100 000 inhabitants; IRR– Incidence rate ratio; Model 1 analyses time between T1-T2, containing W1, W2 and W3; Model 2 analyses time between T2-T3, containing W3, W4 and W5; Model 3 analyses time between T1-T3, containing W1, W2, W3, W4 and W5
*T1 for Model 1 and Model 3 and T2 for Model 2

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