Table 3. Univariable linear regression model comparing severe disease in different phases of epidemic waves in four provinces.

Disease severity core/population	Variable*	Coef.	t statistics	P>|t| (Univariable model)
Khorasan Razavi
	During the peak	0.01	1.48	0.140
	After the peak	-0.02	-1.60	0.109
Khuzestan
	During the peak	0.06	6.44	<0.001
	After the peak	0.11	8.15	<0.001
Kurdistan
	During the peak	0.07	5.05	<0.001
	After the peak	0.05	2.52	0.011
Mazandaran
	During the peak	0.04	2.94	0.003
	After the peak	0.04	2.30	0.020
Total population
	During the peak	0.02	4.70	<0.001
	After the peak	0.03	4.76	<0.001

*"Before the peak" is the reference category.