Table 4.

Vaccine effectiveness (VE) of TIV against influenza-related hospitalization in patients ≥16–64 years (younger adults group)

	Cases	Controls	Unadjusted		Adjusted
	N	N	VE, %	95% CI	VE, %	95% CI
All strains	208	271	35.8	4.5, 56.8	33.2a	−6.7, 58.2
Influenza A	86	110	48.5	1.4, 73.1	42.2b	−24.2, 73.1
A/H1N1	55	68	57.8	2.7, 81.7	68.7c	6.4, 89.5
A/H3N2	13	18	38.2	−599.5, 94.5	–	–
Influenza B	122	161	26.2	−22.2, 55.4	25.4d	−35.4, 58.9
B/Victoria	37	48	25.6	−82.8, 69.7	9.7e	−161.6, 68.9
B/Yamagata	53	70	16.6	−81.1, 61.6	36.9f	−72.5, 76.9

N number of patients, CI Confidence Interval, TIV trivalent influenza vaccine, VE vaccine effectiveness

Covariate (p-value in model):

^a Influenza vaccination (0.092), age (0.018), anti-viral use before admission (0.881), seniors including patient living in dwelling (0.020), pregnancy (0.045);

^b Influenza vaccination (0.160), age (0.192), anti-viral use before admission (0.874) seniors including patient living in dwelling (0.188), pregnancy (0.991);

^c Influenza vaccination (0.038), age (0.173), anti-viral use before admission (0.895) seniors including patient living in dwelling (0.201), pregnancy (0.994);

^d Influenza vaccination (0.335), age (0.045), seniors including patient living in dwelling (0.046), pregnancy (0.099);

^e Influenza vaccination (0.850), age (0.054), seniors including patient living in dwelling (0.888), pregnancy (0.996);

^f Influenza vaccination (0.370), age (0.783), seniors including patient living in dwelling (0.037), pregnancy (0.740)