Table 3. Influenza vaccine effectiveness, considering vaccination history in the current and the two previous seasons in patients ≥ 60 years old admitted to hospital, Valencia Hospital Network for the Study of Influenza (VAHNSI), Valencia, Spain, 2017/18 influenza season (n = 1,477 patients).
| Types, subtypes or lineage of influenza | Vaccinated in either 2015/16 or 2016/17a | Vaccinated in 2017/18 | IVEb | 95% CI |
|---|---|---|---|---|
| All influenzac | No | Yes | 30.16 | −34.21 to 63.65 |
| Yes | Yes | 14.20 | −12.79 to 34.73 | |
| Yes | No | 22.98 | −16.64 to 49.14 | |
| A(H1N1)pdm09d | No | Yes | 80.11 | −53.74 to 97.43 |
| Yes | Yes | 46.41 | 6.78 to 69.20 | |
| Yes | No | 10.60 | −94.00 to 58.80 | |
| A(H3N2)e | No | Yes | −1.47 | −142.01 to 57.46 |
| Yes | Yes | −35.26 | −93.67 to 5.53 | |
| Yes | No | −7.52 | −84.80 to 37.44 | |
| B/Yamagataf | No | Yes | 4.48 | −142.60 to 62.39 |
| Yes | Yes | 39.61 | 8.13 to 60.31 | |
| Yes | No | 50.18 | 2.34 to 74.59 |
CI: confidence interval; GP: general practitioner; IVE: influenza vaccine effectiveness.
a The 2015/16 influenza vaccine comprised an A/California/7/2009 (H1N1)pdm09-like virus, an A/Switzerland/9715293/2013 (H3N2)-like virus and a B/Phuket/3073/2013-like virus (Yamagata lineage). The 2016/17 influenza vaccine comprised an A/California/7/2009 (H1N1)pdm09-like virus, an A/Hong Kong/4801/2014 (H3N2)-like virus and a B/Brisbane/60/2008-like virus (Victoria lineage).
b Taking those individuals not vaccinated in any of the three considered seasons as reference category.
c Adjusted by age, number of chronic conditions, sex, socioeconomic status (occupation), admission in the last 12 months, number of GP visits in the last 3 months, smoking habits, obesity status, days between symptoms onset and swab, hospital and epidemiological week at admission.
d Adjusted by age, sex and epidemiological week at admission.
e Adjusted by age, number of chronic conditions, sex, socioeconomic status (occupation), admission in the last 12 months, number of GP visits in the last 3 months, smoking habits, obesity status, days between symptoms onset and swab, hospital and epidemiological week at admission.
f Adjusted by age, number of chronic conditions, sex, smoking habits and epidemiological week at admission.