Table 3.
Relative vaccine effectiveness (rVE) of trivalent high dose influenza vaccine compared with trivalent/quadrivalent standard dose influenza vaccine.
| MD-IIV3 vaccinees |
Adjusted using a priori variablesa % rVE (95% CI) | Adjusted using a priori and instrumental variablesb % rVE (95% CI) | Adjusted using propensity score weightsc % rVE (95% CI) | Adjusted using Inverse probability weightsc % rVE (95% CI) | ||
|---|---|---|---|---|---|---|
| Cases N (%) | Controls N (%) | |||||
| 2015–2016 | ||||||
| All influenza A | 16 (40) | 241 (43) | 9 (−92, 57) | 3 (−105, 54) | −9 (−158, 54) | −33 (−187, 39) |
| 2016–2017 | ||||||
| All influenza A | 93 (54) | 282 (55) | 8 (−46, 42) | −2 (−65, 37) | 2 (−69, 43) | 11 (−31, 39) |
| Influenza A/H3N2 | 87 (53) | 282 (55) | 10 (−44, 44) | 1 (−61, 39) | 5 (−65, 45) | 15 (−26, 43) |
| 2017–2018 | ||||||
| All influenza A | 90 (47) | 297 (53) | 5 (−45, 38) | 8 (−42, 41) | 6 (−55, 43) | 11 (−33, 40) |
| Influenza A/H3N2 | 77 (46) | 297 (53) | 9 (−41, 42) | 13 (−37, 45) | 7 (−56, 45) | 12 (−34, 42) |
| 2018–2019 | ||||||
| All influenza A | 97 (53) | 452 (58) | −2 (−52, 32) | 13 (−37, 42) | 19 (−27, 48) | 15 (−27, 43) |
| Influenza A/H1N1 | 46 (54) | 452 (58) | −32 (−134, 25) | −23 (−122, 32) | −5 (−98, 44) | −4 (−80, 40) |
| Influenza A/H3N2 | 51 (52) | 452 (58) | 14 (−43, 48) | 30 (−19, 59) | 34 (−17, 63) | 28 (−21, 58) |
| All seasons 2015–2018 | ||||||
| All influenza A | 297 (51) | 1276 (53) | 7 (−16, 26) | 9 (−14, 28) | 10 (−15, 30) | 18 (0, 33) |
| Influenza A/H1N1 | 73 (53) | 1276 (53) | −19 (−80, 21) | −19 (−82, 22) | −14 (−82, 29) | −32 (−94, 11) |
| Influenza A/H3N2 | 218 (50) | 1276 (53) | 14 (−11, 34) | 17 (−8, 36) | 16 (−11, 37) | 27 (9, 42) |
A priori variables = age, race/ethnicity, sex, clinical site, season, interval from onset to enrollment (0–2 days, 3–4 days, 5–7 days), any prior high-risk condition, and bi-week (indicator variable of 2-week blocks of calendar time).
A priori variables plus instrumental variables prior vaccination status, and timing of vaccination. (Excluded a priori variable bi-week because bi-week and timing of vaccination were highly correlated. The relative VEs remain the same when bi-week is included).
Propensity score weights were calculated using a priori variables, instrumental variables and the 120 three way interactions (10 variables, including vaccination status, with three-way interactions). Bi-week is excluded from propensity score modeling.