Table 2.

Incidence of acute respiratory (ARI) and gastrointestinal (AGI) infections, by mode of data collection and age group

		Prospective data collection				Retrospective data collection				Significance (p-value for differences between the study arms
		Person days	Episodes	Incidence per person month (30 days)c	Incidence per person year (365 days)	Person days	Episodes	Incidence per person month (30 days)c	Incidence per person year (365 days)	α = 0.05
ARI	Age groups
	0–3 years	7009	164	0.7 (0.59; 0.82)	8.54	8311	217	0.78 (0.68; 0.89)	9.49	p = 0.31
	4–6 years	5729	100	0.52 (0.43; 0.64)	6.37	5882	103	0.53 (0.43; 0.64)	6.39	p = 1.00
	7–15 years	1891	13	0.21 (0.12; 0.33)	2.51	2828	41	0.43 (0.31; 0.59)	5.29	p = 0.02
	> 15 years	17,274	229	0.4 (0.35; 0.45)	4.84	22,970	330	0.43 (0.39; 0.48)	5.22	p = 0.37
	Total	32387a	507	0.47 (0.42; 0.52)	5.71	40050b	691	0.52 (0.48; 0.56)	6.32	p = 0.10
AGI	Age groups
	0–3 years	7117	48	0.2 (0.16; 0.26)	2.46	8120	53	0.2 (0.15; 0.26)	2.37	p = 0.95
	4–6 years	5792	24	0.12 (0.08; 0.18)	1.51	5721	30	0.16 (0.11; 0.22)	1.91	p = 0.47
	7–15 years	1902	6	0.09 (0.04; 0.20)	1.15	2724	17	0.19 (0.11; 0.30)	2.28	p = 0.21
	> 15 years	17,441	66	0.11 (0.09; 0.15)	1.38	22,370	83	0.11 (0.09; 0.14)	1.35	p = 0.97
	Total	32736a	144	0.13 (0.11; 0.16)	1.61	38994b	183	0.14 (0.12; 0.16)	1.7	p = 0.60

^aMissing information on age for 4 persons (contributing 484 person days), ^bMissing information on age for 1 person (contributing 59 person days), ^cConfidence Intervals (CI’s) in brackets