Table 4. Influenza vaccine effectiveness in preventing laboratory-confirmed cases by healthcare setting, age group and virus (sub)type, northern Spain, 2010/11 to 2015/16.
| Age 50–64 years | Age ≥ 65 years | |||||
|---|---|---|---|---|---|---|
| All patients | Outpatients | Inpatients | All patients | Outpatients | Inpatients | |
| Influenza A(H1N1)pdm09 | ||||||
| Cases, n (% vaccinated) | 273 (15) | 148 (12) | 125 (19) | 227 (55) | 48 (56) | 179 (55) |
| Controls, n (% vaccinated) | 523 (27) | 242 (20) | 281 (32) | 1,118 (66) | 131 (55) | 987 (67) |
| Crude VE, % (95% CI) | 51 (28 to 67) | 49 (7 to 72) | 50 (16 to 70) | 36 (15 to 52) | –1 (–95 to 48) | 40 (18 to 57) |
| Adjusted VE, % (95% CI) a | 56 (31 to 72) | 63 (26 to 82) | 47 (2 to 72) | 25 (–6 to 46) | –20 (–200 to 52) | 31 (1 to 52) |
| Influenza A(H3N2) | ||||||
| Cases, n (% vaccinated) | 175 (17) | 138 (15) | 37 (24) | 299 (62) | 90 (59) | 209 (63) |
| Controls, n (% vaccinated) | 523 (27) | 242 (20) | 281 (32) | 1118 (66) | 131 (55) | 987 (67) |
| Crude VE, % (95% CI) | 43 (11 to 63) | 31 (–24 to 60) | 32 (–51 to 69) | 16 (–10 to 35) | –17 (–102 to 32) | 17 (–14 to 39) |
| Adjusted VE, % (95% CI) a | 36 (–12 to 63) | 40 (–23 to 70) | 39 (–71 to 78) | 14 (–19 to 38) | –48 (–249 to 38) | 21 (–12 to 45) |
| Influenza B | ||||||
| Cases, n (% vaccinated) | 124 (15) | 98 (12) | 26 (23) | 140 (55) | 36 (44) | 104 (59) |
| Controls, n (% vaccinated) | 523 (27) | 242 (20) | 281 (32) | 1118 (66) | 131 (55) | 987 (67) |
| Crude VE, % (95% CI) | 53 (20 to 73) | 45 (–9 to 72) | 36 (–64 to 75) | 37 (9 to 55) | 34 (–38 to 69) | 31 (–4 to 54) |
| Adjusted VE, % (95% CI) a | 47 (–2 to 73) | 55 (–9 to 81) | 13 (–184 to 73) | 41 (10 to 61) | 62 (–7 to 87) | 40 (3 to 63) |
CI: confidence interval; VE: vaccine effectiveness.
a Vaccine effectiveness adjusted by age groups 50–59, 60–69, 70–79 and ≥ 80 years), sex, major chronic conditions, functional dependence, hospitalisation in the previous 12 months, healthcare setting (primary healthcare and hospital), and influenza season and month of sample collection.