Table 3. Influenza vaccine effectiveness in preventing laboratory-confirmed cases by healthcare setting, age and comorbidity in northern Spain, 2010/11 to 2015/16.
| All patients | Outpatients | Inpatients | |
|---|---|---|---|
| All swabbed patients | |||
| Cases, n (% vaccinated) | 1,242 (39) | 557 (26) | 685 (49) |
| Controls, n (% vaccinated) | 1,641 (53) | 373 (32) | 1,268 (60) |
| Crude VE, % (95% CI) | 45 (36 to 53) | 23 (2 to 45) | 35 (22 to 46) |
| Adjusted VE, % (95% CI) a | 31 (18 to 43) | 34 (6 to 54) | 32 (15 to 45) |
| Aged 50–64 years old | |||
| Cases, n (% vaccinated) | 572 (16) | 384 (13) | 188 (21) |
| Controls, n (% vaccinated) | 523 (27) | 242 (20) | 281 (32) |
| Crude VE, % (95% CI) | 49 (31 to 62) | 41 (9 to 62) | 44 (14 to 34) |
| Adjusted VE, % (95% CI) a | 49 (29 to 64) | 56 (29 to 73) | 43 (5 to 66) |
| Aged ≥ 65 years old | |||
| Cases, n (% vaccinated) | 670 (58) | 173 (55) | 497 (59) |
| Controls, n (% vaccinated) | 1,118 (66) | 131 (55) | 987 (67) |
| Crude VE, % (95% CI) | 28 (12 to 41) | 1 (–55 to 37) | 29 (11 to 43) |
| Adjusted VE, % (95% CI) a | 25 (6 to 40) | 3 (–71 to 45) | 29 (9 to 44) |
| Patients without major chronic conditions | |||
| Cases, n (% vaccinated) | 459 (22) | 336 (20) | 123 (28) |
| Controls, n (% vaccinated) | 414 (29) | 203 (20) | 211 (37) |
| Crude VE, % (95% CI) | 31 (6 to 49) | 3 (–49 to 37) | 35 (–6 to 60) |
| Adjusted VE, % (95% CI) a | 32 (–1 to 54) | 23 (–31 to 55) | 42 (–15 to 71) |
| Patients with major chronic conditions | |||
| Cases, n (% vaccinated) | 783 (48) | 221 (36) | 562 (53) |
| Controls, n (% vaccinated) | 1,227 (62) | 170 (47) | 1,057 (64) |
| Crude VE, % (95% CI) | 42 (30 to 51) | 38 (7 to 59) | 36 (21 to 48) |
| Adjusted VE, % (95% CI) a | 32 (16 to 45) | 41 (2 to 65) | 30 (12 to 45) |
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.