Table 1. Person-to-person hepatitis A outbreaks according to the risk factor of the index case in the pre-vaccination (1991–98) and in the post-vaccination (2000–12) periods.

	Number of outbreaks		OR* (95% CI)	P	aOR (95% CI)	P
	Period 1: 1991–98	Period 2: 2000–12
Day care (child)	10	9	3.07 (1.20–7.84)	0.019
Day care (adult)	1	7	0.36 (0.04–2.94)	0.338
Immigrant	5	58	0.17 (0.07–0.44)	< 0.001	0.19 (0.07–0.49)	0.005
Household contact	29	60	1.35 (0.79–2.31)	0.275
School contact	23	17	4.34 (2.18–8.63)	< 0.001	2.72 (1.35–5.48)	< 0.001
Travel	1	5	0.51 (0.06–4.37)	1
MSM	0	26	0.04 (0.002–0.74)	0.003	0.04 (0.002–0.67)	0.026
Others** and unknown***	17	37	1.21 (0.64–2.29)	0.555
All outbreaks	86	219	–

MSM, men who have sex with men; OR, Odds ratio; aOR, adjusted odds ratio; CI, confidence interval; *comparing each category of risk factor with all the others; **others, adopted children; ***unknown, outbreaks with unknown risk factors