Table 4.
Absolute and Relative Influenza Vaccine Effectiveness for Prevention of Laboratory-Confirmed Influenza Hospitalization Among Adults Aged ≥65 Years, HAIVEN Study, 2015–2016 to 2016–2017
| N | Influenza-Positive Cases/Total (%) | Adjusted VE (95% CI)a | Relative VEb | |||||
|---|---|---|---|---|---|---|---|---|
| Unvaccinated | SD-IIV | HD-IIV | Any Vaccine | SD-IIV | HD-IIV | (95% CI) | ||
| Influenza type/Subtype | ||||||||
| All influenza A/B | 1487 | 92/380 (24) | 87/485 (18) | 98/622 (16) | 21 (−15, 46) | 6 (−42, 38) | 32 (−3, 54) | 27 (−1, 48) |
| Influenza A(H1N1)pdm09 | 1266 | 23/311 (7) | 18/416 (4) | 15/539 (3) | 30 (−54, 68) | 23 (−84, 68) | 36 (−54, 74) | 17 (−76, 61) |
| Influenza A(H3N2) | 1360 | 46/334 (14) | 45/443 (10) | 59/583 (10) | 8 (−54, 45) | −6 (−86, 40) | 18 (−42, 53) | 23 (−19, 50) |
| Influenza B/Yamagata | 1264 | 20/308 (6) | 17/415 (4) | 17/541 (3) | 50 (−1, 75) | 31 (−50, 68) | 62 (16, 83) | 44 (−13, 73) |
| Season | ||||||||
| 2015–2016 | 500 | 28/132 (21) | 28/197 (14) | 19/171 (11) | 35 (−31, 68) | 26 (−58, 66) | 44 (−23, 75) | 24 (−46, 61) |
| 2016–2017 | 987 | 64/248 (26) | 59/288 (20) | 79/451 (18) | 19 (−27, 48) | 3 (−58, 41) | 29 (−15, 56) | 27 (−8, 50) |
| Age group | ||||||||
| 65–74 y | 792 | 56/241 (23) | 42/259 (16) | 43/292 (15) | 14 (−41, 48) | 0 (−73, 43) | 25 (−30, 57) | 25 (−22, 54) |
| ≥75 y | 695 | 36/139 (26) | 45/226 (20) | 55/330 (17) | 32 (−21, 62) | 18 (−54, 56) | 40 (−10, 67) | 27 (−15, 54) |
Abbreviations: CI, confidence interval; HAIVEN, Hospitalized Adult Influenza Vaccine Effectiveness Network; HD-IIV, high-dose inactivated influenza vaccine; SD-IIV, standard-dose inactivated influenza vaccine; VE, vaccine effectiveness.
aAdjusted for site, season, age, prior season influenza vaccination, Charlson comorbidity index. Models stratified by season do not adjust for season. Models stratified by age group do not adjust for age.
bRelative VE of HD-IIV compared to SD-IIV was calculated by comparing odds of influenza among patients who received HD-IIV versus those who received SD-IIV in a model using the whole study sample (including unvaccinated participants).