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Table 5 Vaccine effectiveness (VE) of TIV against influenza-related hospitalization by early/late season in patients ≥16 years, ≥16–64 years, and ≥65 years

From: Influenza vaccine effectiveness against influenza-related hospitalization during a season with mixed outbreaks of four influenza viruses: a test-negative case-control study in adults in Canada

 

Influenza Type

Cases

Controls

Unadjusted

Adjusted

  

N

N

VE, %

95% CI

VE, %

95% CI

Age ≥ 16 years (all ages)

Early season

 All strains

265

423

48.6

27.9, 63.3

54.4a

29.7, 70.4

 Influenza B

148

230

41.0

8.4, 62.1

44.8b

0.3, 69.5

Late season

 All strains

263

412

33.8

6.6, 53.0

29.7c

−5.3, 53.1

 Influenza B

198

304

34.1

2.8, 55.4

33.1d

−5.2, 57.5

Age ≥ 16–64 years (younger adults)

Early season

 All strains

109

131

59.0

27.6, 76.8

65.7e

28.2, 83.6

 Influenza B

55

68

60.1

12.7, 81.8

67.1f

2.7, 88.9

Late season

 All strains

99

140

−8.5

−95.0, 39.6

−36.1g

−171.2, 31.7

 Influenza B

67

93

−27.7

−175.5, 36.7

−52.3h

−251.6, 34.0

Age ≥ 65 years (older adults)

Early season

 All strains

156

292

41.2

9.8, 61.7

52.5i

8.0, 75.5

 Influenza B

93

162

27.4

−25.9, 58.2

36.3j

−45.1, 72.0

Late season

 All strains

164

272

48.6

21.3, 66.4

62.4k

29.9, 79.9

 Influenza B

131

211

50.9

21.2, 69.4

69.3l

37.4, 84.9

  1. N number of patients, CI Confidence Interval, TIV trivalent influenza vaccine
  2. Early season defined as admissions prior to the admission date of the median influenza case enrolled; Late season defined as admissions after the date of admission of the median influenza case enrolled
  3. Covariate (p value in model):
  4. a Influenza vaccination (<0.001), age (0.116), antiviral use before onset of illness (0.821), admission from long term care facility (0.001), obesity (0.017), exposed to children aged <5 years in household (0.536), current or past smoker (0.015), medications before onset of illness (0.325);
  5. b Influenza vaccination (0.049), age (0.099), antiviral use before onset of illness (0.992), admission from long term care facility (<0.001), obesity (0.020), exposed to children aged <5 years in household (0.447), current or past smoker (0.001), medications before onset of illness (0.515);
  6. c Influenza vaccination (0.088), age (0.383), antiviral use before onset of illness (0.988), admission from long term care facility (0.960), obesity (0.859), exposed to children aged <5 years in household (0.030), current or past smoker (0.003), medications before onset of illness (0.007);
  7. d Influenza vaccination (0.082), age (0.150), antiviral use before onset of illness (0.992), admission from long term care facility (0.884), obesity (0.764), exposed to children aged <5 years in household (0.060), current or past smoker (0.002), medications before onset of illness (0.018);
  8. e Influenza vaccination (0.005), age (0.035), antiviral use before onset of illness (0.998), seniors including patient living in the dwelling (0.129), pregnancy (0.994);
  9. f Influenza vaccination (0.045), age (0.021), seniors including patient living in the dwelling (0.061), pregnancy (0.995), (no patients used antivirals before onset of illness);
  10. g Influenza vaccination (0.381), age (0.383), antiviral use before onset of illness (0.992), seniors including patient living in the dwelling (0.046), pregnancy (0.264);
  11. h Influenza vaccination (0.324), age (0.993), seniors including patient living in the dwelling (0.173), pregnancy (0.188), (no patients used antivirals before onset of illness);
  12. i Influenza vaccination (0.027), age (0.151), antiviral use before onset of illness (0.991), frailty index prior to admission (0.057), exposed to children aged <5 years in household (0.179), medications before onset of illness (0.051);
  13. j Influenza vaccination (0.283), age (0.220), antiviral use before onset of illness (0.995), frailty index prior to admission (0.030), exposed to children aged <5 years in household (0.399), medications before onset of illness (0.031);
  14. k Influenza vaccination (0.002), age (0.992), antiviral use before onset of illness (0.993), frailty index prior to admission (0.076), exposed to children aged <5 years in household (0.107), medications before onset of illness (0.397);
  15. l Influenza vaccination (0.001), age (0.673), antiviral use before onset of illness (0.993), frailty index prior to admission (0.043), exposed to children aged <5 years in household (0.467), medications before onset of illness (0.339)
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BMC Infectious Diseases

ISSN: 1471-2334

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