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Table 3 Effectiveness of the trivalent influenza 2011–12 vaccine against influenza A(H3N2) in target group for vaccination by time since vaccination, in the early and late phase of the season, cycEVA study (weeks 52/2011 – 14/2012), Spain

From: Effectiveness of influenza vaccine against laboratory-confirmed influenza, in the late 2011–2012 season in Spain, among population targeted for vaccination

Influenza activity phasea

Time since vaccination

Cases and controls (N/N)

Vaccinated cases and controls (N/N)

OR

Influenza VE % (95% CI)

Trend p valued

Early phase

45–75 days

110/63

1/8

Crude

94 (48;99)

0.119

Adjusted

95 (45;99)b

76–105 days

128/66

19/11

Crude

13 (−96;53)

Adjusted

48 (−31;80)c

106–135 days

131/64

22/9

Crude

−23 (−186;47)

Adjusted

36 (−71;76)c

Late phase

39–81 days

29/16

0/1

Crude

0

0.518

Adjusted

0

82–123 days

47/21

18/6

Crude

−55 (−372;49)

Adjusted

−9 (−379;75)b

124–166 days

55/26

26/11

Crude

−22 (−213;52)

Adjusted

15 (−214;77)b

  1. aEarly phase: December 2011 – first half of February 2012; Late phase: Second half of February – April 2012. bModel adjusted for age groups (0–4, 5–14, 15–64 and >64 years), and week of swabbing. cModel adjusted for age groups (0–4, 5–14, 15–64 and >64 years), smoking habit, and week of swabbing. dTest for trend using time since vaccination as continuous.