Table 1. Estimates of vaccine effectiveness for a single dose of the mumps-containing vaccine by time since vaccination in two schools of Guangdong, China, 2012*.

School	Number of years since vaccination	Cases	AR (%)	VE (%)	95% CI
Day-care centre	No vaccine	11	23.9	Ref	−
	< 3	5	7.6	66	8–87
	3–6	13	18.3	23	-56–62
Primary school	No vaccine	3	18.8	Red	−
	< 3	2	7.1	62	5–97
	3–6	13	20.3	−	−
Total	No vaccine	14	22.6	Ref	−
	< 3	7	7.9	65	19–85
	3–6	26	19.3	15	-52–52

AR – attack rate; VE – vaccine effectiveness; CI – confidence interval.

* Students with unknown vaccination status or two doses of mumps vaccination before the outbreak were excluded.