Table 2.

Reported Varicella Outbreaks during 2005–2012, Data from 9 States: Selected Variables

Variable	2005–2006		2007–2009		2010–2012		p-value for trend test
Varicella Outbreak Data (N=1,015 outbreaks)
Total # Outbreaks	387		457		171
	#	%	#	%	#	%
Settinga
Daycare	7	1.9	8	1.9	7	4.1	0.0084b
School	367	97.1	410	95.1	151	88.8	0.0014b
Otherd	4	1.1	13	3.0	12	7.1	<0.0001b
Totale	378	97.7	431	94.3	170	99.4
Outbreak Size
<5 cases	6	1.6	16	3.5	25	14.6	<0.0001b
5–9 cases	142	36.7	223	48.8	87	50.9	0.0005b
10–20 cases	159	41.1	147	32.2	42	24.6	0.0001b
21–50 cases	73	18.9	63	13.8	15	8.8	0.0006b
≥51 cases	7	1.8	8	1.8	2	1.2	0.9713b
Totale	387	100.0	457	100.0	171	100.0
Varicella Case Data (N=13,595 Cases)
Total # Cases	5,812		6,020		1,763
	#	%	#	%	#	%
Age (% among cases with non-missing data) (N=8,059 Cases)
<1 year	5	0.2	26	0.8	16	0.9	0.0001c
1–4 years	93	3.2	126	3.7	115	6.7	<0.0001b
5–9 years	2,187	75.5	2,276	66.0	774	45.2	<0.0001b
10–14 years	589	20.3	961	27.9	669	39.1	<0.0001b
15–19 years	16	0.6	41	1.2	63	3.7	<0.0001b
≥20 years	7	0.2	20	0.6	75	4.4	<0.0001b
Totale	2,897	49.8	3,450	57.3	1,712	97.1
Vaccination Status (% among cases with non-missing data) (N=7,454 Cases)
Unvaccinatedf	513	21.9	766	20.6	469	33.8	<0.0001b
Vaccinatedf	1,825	78.1	2,961	79.4	920	66.2	<0.0001b
Totale	2,338	40.2	3,727	61.9	1,389	78.8
Number Vaccine Doses (% among vaccinated cases) (N=3,850 Cases)
1-dose	1,077	59.0	1,838	62.1	613	66.6	0.3588b
2-dose	1	0.1	97	3.3	224	24.3	<0.0001b
Totalg	1,078	59.1	1,935	65.3	837	91.0

^aInformation on outbreak setting missing for 36 outbreaks.

^bCochrane Armitage Trend test used.

^cExact Cochrane Armitage Trend test used.

^dOther settings include community, correctional facilities, healthcare facilities, and universities.

^ePercentages calculated out of total number of reported outbreaks or cases by study period.

^fWe excluded those with prior varicella disease if information was available on prior disease history.

^gPercentages calculated out of total reported number of vaccinated cases by study period.