Table 2.
Vaccine effectiveness (VE) for trivalent/quadrivalent standard dose influenza vaccine (SD-IIV3/4) and for trivalent high dose influenza vaccine (HD-IIV3) for four seasons (2015–2018) against any influenza A, A/H1N1 and A/H3N2 viruses.
| Outcome | SD-IIV3/4 (N = 1420) versus unvaccinated (N = 868) |
HD-IIV3 (N = 1573) versus unvaccinated (N = 868) |
||
|---|---|---|---|---|
| Unadjusted % VE (95% CI) | Adjusteda% VE (95% CI) | Unadjusted % VE (95% CI) | Adjusteda % VE (95% CI) | |
| 2015–2016 | ||||
| All influenza A | 49 (7, 72) | 53 (11, 75) | 56 (14, 77) | 52 (−7, 78) |
| 2016–2017 | ||||
| All influenza A | 14 (−27, 42) | 25 (−14, 51) | 16 (−23, 42) | 29 (−12, 55) |
| Influenza A/H3N2 | 17 (−24, 44) | 27 (−11, 53) | 21 (−15, 46) | 32 (−7, 57) |
| 2017–2018 | ||||
| All influenza A | 5 (−38, 35) | 5 (−45, 38) | 27 (−6, 50) | 13 (−36, 45) |
| Influenza A/H3N2 | 5 (−39, 36) | 2 (−52, 37) | 31 (−2, 54) | 13 (−40, 46) |
| 2018–2019 | ||||
| All influenza A | 10 (−31, 39) | 26 (−14, 52) | 26 (−6, 49) | 29 (−11, 54) |
| Influenza A/H1N1 | 19 (−35, 51) | 47 (3, 71) | 31 (−12, 58) | 26 (−35, 59) |
| Influenza A/H3N2 | 1 (−64, 40) | 5 (−67, 46) | 21 (−29, 52) | 27 (−31, 59) |
| 2015–2018 | ||||
| All influenza A | 17 (−2, 32) | 24 (5, 39)b | 25 (8, 38) | 29 (10, 44)b |
| Influenza A/H1N1 | 31 (−1, 52) | 40 (10, 61)c | 30 (−1, 51) | 30 (−7, 54)b |
| Influenza A/H3N2 | 14 (−8, 31) | 19 (−5, 37)b | 25 (6, 40) | 31 (9, 47)b |
Adjusted for a priori variables age, race/ethnicity, sex, clinical site, interval from onset to enrollment, any prior high-risk condition, and bi-week (indicator variable of 2-week blocks of calendar time).
Adjusted for a priori variables age, race/ethnicity, sex, clinical site, season, interval from onset to enrollment, any prior high-risk condition, and bi-week (indicator variable of 2-week blocks of calendar time).
Season included as continuous variable, because there was no A/H1N1 in 2016–17 (There was no change in VE, when season was excluded from the model).