Table 4.

Adjusted Vaccine Effectiveness for Influenza Type and Subtype

	Influenza Positive (Cases)		Influenza Negative (Controls)		Adjusteda
	No. Vaccinated/Total	% Vaccinated	No. Vaccinated/Total	% Vaccinated	VE %	95% CI
Influenza A
All ages	212/700	30	1958/3684	53	60	53–67
6 months–8 years	71/193	37	903/1431	63	64	50–74
9–49 years	71/357	20	534/1425	37	55	39–66
≥50 years	70/150	47	521/828	63	46	21–63
Influenza B
All ages	105/325	32	1958/3684	53	60	48–69
6 months–8 years	55/167	33	903/1431	63	62	45–74
9–49 years	33/121	27	534/1425	37	38	2–61
≥50 years	17/37	46	521/828	63	47	−6 to 74
Influenza A H1N1
All ages	94/369	25	1958/3684	53	66	56–74
6 months–8 years	28/73	38	903/1431	63	60	33–77
9–49 years	34/220	15	534/1425	37	66	47–76
≥50 years	32/76	42	521/828	63	45	9–67
Influenza A H3N2
All ages	115/328	35	1958/3684	53	54	42–64
6 months–8 years	43/120	36	903/1431	63	66	48–78
9–49 years	35/135	26	534/1425	37	39	7–60
≥50 years	37/73	51	521/828	63	52	18–72

Abbreviations: CI, confidence interval; VE, vaccine effectiveness.

^a Adjusted for study site, age in years, race, insurance, enrollment site, and high-risk condition.