Table 3.
Effectiveness and relative effectiveness of recombinant and standard dose influenza vaccines against RT-PCR-confirmed influenza during the 2018–2019 and 2019–2020 influenza seasons.
| Group | Adjusted Vaccine Effectiveness,* % (95% CI) |
Relative Vaccine Effectiveness of Recombinant vs. Standard Dose Influenza Vaccine, % (95% CI) |
||||
|---|---|---|---|---|---|---|
| Recombinant (a) |
Standard dose (b) |
Unadjusted (c) |
Adjusted using a priori variables** (d) |
Adjusted using propensity score (e) | Adjusted using inverse probability weights (f) |
|
| Overall | 40 (25, 51) | 35 (20, 47) | 6 (−24, 29) | 11 (−19, 34) | 13 (−19, 37) | 11 (−20, 33) |
| Age 18–49 years | 50 (33, 61) | 44 (28, 56) | 8 (−30, 35) | 15 (−24, 40) | 11 (−29, 38) | 9 (−31, 36) |
| Age 50–64 years | 14 (−25, 40) | 13 (−23, 39) | 3 (−54, 39) | 6 (−52, 42) | 4 (−56, 41) | −2 (−66, 36) |
| Female sex | 37 (18, 51) | 29 (10, 45) | 6 (−31, 32) | 11 (−25, 37) | 10 (−28, 37) | 8 (−31, 35) |
| Male sex | 48 (20, 65) | 44 (20, 61) | 9 (−54, 46) | 9 (−62, 49) | 3 (−76, 47) | 6 (−64, 46) |
| High-risk condition | 43 (25, 56) | 20 (−8, 40) | 27 (−6, 49) | 30 (−1, 52) | 32 (−1, 54) | 26 (−8, 50) |
| No high-risk condition | 31 (1, 52) | 47 (30, 60) | −34 (−109, 14) | −35 (−115, 15) | −22 (−95, 24) | −25 (−98, 20) |
| 2018–2019 season | 43 (15, 62) | 40 (13, 59) | 5 (−59, 43) | 8 (−57, 46) | 9 (−58, 48) | 7 (−60, 46) |
| 2019–2020 season | 38 (20, 52) | 33 (15, 48) | 7 (−30, 33) | 9 (−30, 36) | 11 (−28, 38) | 9 (−30, 35) |
Bold indicates non-overlapping confidence intervals.
*Adjusted vaccine effectiveness for recombinant and standard dose vaccines vs. no vaccination.
**Multivariable logistic regression model adjusted for age, race, sex, season, and high-risk conditions, except that the stratified variable is not included as an adjustment in its own analysis.
Propensity score: Generalized Boosted Regression Method was used to calculate the propensity score using TWANG (Toolkit for Weighting and Analysis of Nonequivalent Groups).