Table 2.

Vaccine Effectiveness (VE) against influenza A(H3N2) viruses excluding the 2014–15 season by age group and receipt of vaccination in the year prior to enrollment among adults vaccinated during the current season.

	Current and prior season vaccination			Current season vaccination only
	n (%)	aVE* (95% CI)	Interaction p value†	n (%)	aVE* (95% CI)	Interaction p value†
18–49 years (n = 5,077)	1,251 (25%)	39 (19, 54)	–	905 (18%)	42 (21, 57)	–
50–64 years (n = 2,543)	1,130 (44%)	60 (41, 73)	0.36	423 (17%)	56 (29, 72)	0.55
≥65 years (n = 1,599)	1,053 (66%)	0.9 (−77, 45)	0.15	197 (12%)	14 (−74, 58)	0.36
65–74 years (n = 1,011)	615 (61%)	−22 (−159, 43)	0.07	152 (15%)	6.1 (−130, 62)	0.30
≥75 years (n = 588)	438 (74%)	41 (−64, 79)	0.64	45 (7.7%)	48 (−109, 87)	0.84

^*Adjusted for site, age (spline, month), month of enrollment, sex, race/ethnicity, presence of ≥1 high-risk condition, interval from symptom onset to enrollment, self-reported general health status, and season

^†p value for the interaction term of age and vaccination (for the test of significance of the interaction term) in model using adults aged 18–49 years as a comparison group