Table 5. Pooled adjusted seasonal vaccine effectiveness against hospitalised influenza B among elderly people overall and by risk groups, I-MOVE + study, Europe, influenza season 2015/16.
| Model used for adjustmenta | Vaccinated /cases |
Vaccinated /controls |
Adjusted IVE | 95% CI | |
|---|---|---|---|---|---|
| Overall | |||||
| Overall | Initial | 50/110 | 588/1,015 | 51.8 | 23.7 to 69.5 |
| Overall | Full | 46/101 | 544/948 | 47.0 | 13.1 to 67.7 |
| By risk groups | |||||
| At least one underlying condition | Initial | 47/97 | 536/929 | 50.2 | 18.7 to 69.4 |
| Initial plus severity | 49.4 | 17.5 to 69.0 | |||
| Diabetes mellitus | |||||
| No | Initial | 33/72 | 404/696 | 40.9 | −7.1 to 67.4 |
| Yes | Initial | 13/30 | 152/272 | 62.1 | 5.8 to 84.7 |
| Initial plus severity | 62.0 | 5.3 to 84.8 | |||
| Heart disease | |||||
| No | Initial | 16/44 | 211/368 | 66.5 | 27.6 to 84.5 |
| Yes | Initial | 32/61 | 354/614 | 36.3 | −22.2 to 66.8 |
| Initial plus severity | 36.1 | −22.9 to 66.7 | |||
| Lung disease | |||||
| No | Initial | 27/61 | 258/502 | 32.8 | −28.6 to 64.8 |
| Yes | Initial | 22/45 | 305/475 | 60.5 | 19.2 to 80.6 |
| Initial plus severity | 59.9 | 18.2 to 80.4 | |||
| Vaccine type | |||||
| Inactivated subunit | Initial | 20/61 | 207/542 | 49.0 | 13.5 to 70.0 |
| Inactivated split virion | Initial | 30/74 | 332/652 | 54.1 | 18.9 to 74.0 |
| Sensitivity analyses | |||||
| two-stage model | two-stageb | 48/86 | 551/858 | 47.0 | 11.9 to 68.2 |
| Restricted to patients swabbed within 3 days | Initial | 31/54 | 358/585 | 25.0 | −50.5 to 62.6 |
| Restricted to patients not receiving antivirals before swabbing | Initial | 46/99 | 577/985 | 52.3 | 22.8 to 70.5 |
CI: confidence interval; I MOVE+: Integrated Monitoring of Vaccines in Europe plus; IVE: influenza vaccine effectiveness.
a Initial: one-stage model adjusted for study site, date of onset and age (modelled as restricted cubic splines). Full: one-stage model adjusted for study site, date of symptom onset, age (modelled as restricted cubic splines), lung, heart, renal disease, diabetes mellitus, cancer, obesity and hospitalisation in the previous year Severity: hospitalisations for underlying conditions in the previous year.
b Croatia, Hungary, Italy, Lithuania, the Netherlands, Poland, Portugal and Romania were excluded from the two-stage analyses because there were no vaccinated controls and/or cases, respectively.