Table 4. Estimates of effectiveness of hand sanitiser on outcome measures.

Outcome	Number Children (34 Schools per Group)		Control Group		Hand Sanitiser Group		IRR, Hand Sanitiser versus Control (95% CI)	p-Value	ICC* (95% CI)
	Control Group	Hand Sanitiser Group	Number of Events (Child-Days of Follow-Up)	Rate (per 100 Child-Days) or Percent	Number of Events (Child-Days of Follow-Up)	Rate (per 100 Child-Days) or Percent
Primary outcome
Number of absence episodes due to any illness‡	1,142	1,301	1,291 (111,451)	1.16	1,542 (127,471)	1.21	1.06 (0.94, 1.18)	0.346	0.018 (0.012, 0.043)
Secondary outcomes for follow-up children
Number of absence episodes due to respiratory illness‡	1,142	1,301	891 (111,451)	0.80	1,069 (127,471)	0.84	1.05 (0.92, 1.20)	0.439	0.015 (0.011, 0.037)
Number of absence episodes due to gastrointestinal illness‡	1,142	1,301	159 (111,451)	0.14	196 (127,471)	0.15	1.11 (0.82, 1.52)	0.490	0.027 (0.023, 0.066)
Length of illness absence episode (total number of days child absent from school)‡	703	827	2,205 (68,786)	3.21	2,771 (80,981)	3.42	1.07 (0.96, 1.19)	0.198	0.020 (0.013, 0.051)
Length of illness episode (number of days from first to last absence day)↑	703	827	3,239 (96,302)	3.36	4,078 (113,369)	3.60	1.07 (0.96, 1.20)	0.211	0.023 (0.017, 0.061)
Number of episodes where at least one other adult in the household had the same illness after the child‡	703	826	192 (68,786)	0.28	249 (80,881)	0.31	1.08† (0.91, 1.30)	0.373	0.000†
Number of episodes where at least one other child in the household had the same illness after the child‡	703	826	226 (68,786)	0.33	301 (80,881)	0.37	1.11† (0.94, 1.30)	0.217	0.000†
Secondary outcomes for all children (school-level analysis) **
Number of absence episodes for any reason	7,478	9,022	23,900 (747,800)	3.20	26,944 (902,200)	2.99	0.94 (0.84, 1.05)	0.283
Length of absence episode for any reason	7,478	9,022	43,186 (747,800)	5.78	48,090 (902,200)	5.33	0.93 (0.81, 1.07)	0.289
Adverse events
Skin reactions	970	1,106	100	10.3%	115	10.4%	1.01† (0.78, 1.30) [OR]	0.946	0.000†

Estimates obtained from marginal models using GEEs with an exchangeable correlation structure and robust variance estimation. All models include the stratification variable “city” (Invercargill, Dunedin, or Christchurch).

*ICC point estimates are those resulting from the GEE models with no adjustment for the stratification variable. Confidence intervals for the ICCs were bootstrapped using the combination of the bootstrap and xtgee commands in Stata. Bootstrapping allowed for the clustering of observations within schools (using both the cluster() and idcluster() options). Bias-corrected 95% bootstrap confidence intervals were calculated from 5,000 replicates.

^‡The exposure period was the number of school days.

^↑The exposure period was the period the child was enrolled in the study minus the length of the school holidays.

^†The ICC point estimate resulting from the GEE model for these outcomes was negative. In this circumstance, the model GEE model was refitted with an independent correlation structure, making the assumption that in the context of a cluster-based evaluation such as this, negative ICCs are more likely to occur through sampling error than because of a true negative ICC [20],[21]. Assuming an independent correlation provides more conservative estimates of the estimated standard errors.

**Data aggregated to the level of the school, and analysed at the school level. The exposure period was calculated as the average school roll over the period of the trial multiplied by 100 (the number of school days encompassed by the trial period).