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. 2011 May 10;6(5):e19621. doi: 10.1371/journal.pone.0019621

Table 6. Field effectiveness of seasonal vaccines, by case definition, age group and study period.

Excluding pandemic vaccine recipients Including pandemic vaccine recipients
Age group FVE (%) 95% CI FVE (%) 95% CI
ILI, epidemic period
Vaccinated for3 weeks or at an unknown date are considered unvaccinated 6 m–4 y 77 (59–89) 72 (54–85)
5–14 84 (78–89) 87 (83–91)
15–64 52 (44–59) 47 (38–54)
≥65 19 (−14–42) 21 (−10–44)
All ages 61 (5666) 63 (5867)
Vaccinated for3 weeks are considered unvaccinated. Vaccinated at an unknown date are considered vaccinated. 6 m–4 y 75 (56–87) 70 (51–84)
5–14 83 (77–88) 87 (82–90)
15–64 47 (39–55) 42 (33–50)
≥65 14 (−20–38) 17 (−16–40)
All ages 58 (5363) 60 (5564)
All vaccinees are considered vaccinated, regardless of the injection date 6 m–4 y 67 (44–82) 62 (42–77)
5–14 69 (60–76) 79 (73–83)
15–64 41 (33–49) 41 (33–48)
≥65 −7 (−50–23) −2 (−43–27)
All ages 47 (4253) 54 (4958)
ILI, post-epidemic period
Vaccinated for3 weeks or at an unknown date are considered unvaccinated 6 m–4 y 54 (−112–97) −18 (−220–71)
5–14 61 (−22–94) 61 (7–88)
15–64 7 (−32–37) 7 (−27–33)
≥65 25 (−52–62) 39 (−23–70)
All ages 19 (−1041) 19 (−539)
Vaccinated for3 weeks are considered unvaccinated. Vaccinated at an unknown date are considered vaccinated. 6 m–4 y 54 (−112–97) −18 (−220–71)
5–14 61 (−22–94) 61 (7–88)
15–64 7 (−32–37) 4 (−30–31)
≥65 3 (−99–52) 22 (−62–61)
All ages 14 (−1638) 15 (−1135)
All vaccinees are considered vaccinated, regardless of the injection date 6 m–4 y 54 (−108–97) −16 (−216–72)
5–14 61 (−23–94) 62 (8–88)
15–64 −4 (−47–28) −7 (−44–22)
≥65 −6 (−119–47) 17 (−72–59)
All ages 5 (−2731) 7 (−2129)
Laboratory-confirmed influenza
Vaccinated for3 weeks or at an unknown date are considered unvaccinated 6 m–4 y 74 (18–96) 77 (29–96)
5–14 60 (25–82) 65 (40–82)
15–64 64 (36–82) 59 (29–78)
All ages 60 (4174) 61 (4474)
Vaccinated for3 weeks are considered unvaccinated. Vaccinated at an unknown date are considered vaccinated. 6 m–4 y 74 (18–96) 77 (29–96)
5–14 50 (11–75) 59 (31–78)
15–64 29 (−11–57) 24 (−16–53)
All ages 38 (1457) 43 (2360)
All vaccinees are considered vaccinated, regardless of the injection date 6 m–4 y 31 (−51–75) 46 (−18–81)
5–14 26 (−22–59) 48 (18–69)
15–64 22 (−18–51) 25 (−12–52)
All ages 20 (−742) 35 (1452)