Skip to main content

Table 4 Estimates of the annual average and seasonal prevented fraction and number of averted influenza hospitalizations and deaths attributed to the vaccine program, for seasons 2014/15 to 2016/17

From: Impact of national influenza vaccination strategy in severe influenza outcomes among the high-risk Portuguese population

IRE

Season

Average

2014/15

2015/16

2016/17

Hospitalization

≥ 65 years

NAE (n) [95%CI]

1124 [443–1863]

1644 [460–2799]

1957 [1326–2657]

1584 [1058–2097]

PF (%)[95%CI]

14.3 [6.2–21.6]

24.3 [8.2–35.4]

24.6 [18.1–30.7]

21.0 [15.1–26.1]

NNV (n)[95%CI]

890 [565–2233]

621 [384–2050]

616 [473–882]

741 [553–1426]

< 65 years with chronic condition

NAE (n) [95%CI]

222 [42–383]

218 [106–326]

311 [135–473]

249 [158–337]

PF (%)[95%CI]

15.6 [3.3–24.1]

16.9 [9.1–23.4]

23.2 [11.6–31.5]

18.5 [12.5–23.4]

NNV (n) [95%CI]

2657 [1628–10,924]

2564 [1857–5172]

2200 [1540–4957]

2619 [1921–6015]

Deaths

≥ 65 years

NAE (n) [95%CI]

409 [81-721]

281 [52-489]

427 [95-743]

371 [198-541]

PF (%) [95%CI]

27.7 [7.0-40.1]

27.5 [6.7-40.1]

31.9 [9.4-45.0]

29.0 [18.0-37.4]

NNV (n) [95%CI]

2416 [1459-10,267]

3613 [2166-15,078]

2796 [1633-10,422]

3241 [1845-10,141]

< 65 years with chronic condition

NAE (n) [95%CI]

13 [3–22]

10 [2–49]

12 [3–20]

12 [6–16]

PF (%)[95%CI]

18.9 [4.8–27.9]

17.9 [4.3–26.1]

22.0 [6.5–31.7]

19.5 [11.8–25.4]

NNV (n)[95%CI]

45,211 [29,413–176,520]

54,149 [35,348–205,119]

58,216 [37,146–206,237]

57,230 [37,610–176,457]

  1. IRE influenza related event, NAE number of averted events, CI confidence interval, PF prevented fraction, NNV number needed to vaccinate