Table 3. Effectiveness of Influenza Vaccine for Children, by Vaccine Doses (6m/o-12y/o).

	Vaccine Doses	Cases	Controls	OR	95% CI
Any Influenza	none	1274	1076	0.62 (non vs once)	0.50–0.76
	once	172	235	0.54 (non vs twice)	0.48–0.62
	twice	646	1004	0.88 (once vs twice)	0.71–1.10
Type A	none	587	1076	0.48 (non vs once)	0.36–0.65
	once	62	235	0.35 (non vs twice)	0.29–0.42
	twice	191	1004	0.72 (once vs twice)	0.52–0.99
A(H1N1)pdm a	none	47	177	0.38 (non vs once)	0.38–1.11
	once	4	40	0.20 (non vs twice)	0.10–0.38
	twice	12	228	0.53 (once vs twice)	0.16–1.71
Type B	none	687	1076	0.73 (non vs once)	0.57–0.94
	once	110	235	0.71 (non vs twice)	0.61–0.82
	twice	455	1004	0.97 (once vs twice)	0.75–1.25

a Among the 4 hospitals which used IRDTs that can detect H1N1pdm09.