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. 2023 Feb 21;19(1):2177461. doi: 10.1080/21645515.2023.2177461
Baseline demographics for non-immunocompromised adults 18–64 years old, excluding recipients of other advanced (non-RIV4) vaccines
Measures Total,
N = 5,289
Vaccine received
Vaccination status
Recombinant,
n = 509
Standard dose (SD),
n = 332
P value recombinant vs. SD Vaccinated,
n = 841
Unvaccinated,
n = 4,448
p Value vaccinated vs. unvaccinated
Age, Mean (SD) 38.4 (13.4) 41.4 (13.3) 41.6 (14.2) 0.853 41.5 (13.7) 37.8 (13.2) <.001
White race, ref. = nonwhite, n (%) 3,853 (72.9) 373 (73.3) 268 (80.7) 0.007 641 (76.2) 3,212 (72.2) <.001
Female sex, ref. = male, n (%) 3,307 (62.5) 372 (73.1) 218 (65.7) 0.021 590 (70.1) 2,717 (61.1) <.001
Age Group, n (%)       0.918     <.001
18–49 years 3,063 (57.9) 245 (48.1) 161 (48.5)   406 (48.3) 2,657 (59.7)  
50–64 years 2,226 (42.1) 264 (51.9) 171 (51.5)   435 (51.7) 1,791 (40.3)  
Influenza case, ref. = non-case, n (%) 1,792 (33.9) 124 (24.4) 81 (24.4) 0.991 205 (24.4) 1,587 (35.7) <.001
High-risk condition,
ref. = no, n (%)
2,131 (40.3) 355 (69.7) 153 (46.1) <.001 508 (60.4) 1,623 (36.5) <.001
Season, n (%)       <.001     <.001
2018–2019 1,168 (22.1) 142 (27.9) 138 (41.6)   280 (33.3) 888 (20.0)  
2019–2020
4,121 (77.9)
367 (72.1)
194 (58.4)
 
561 (66.7)
3,560 (80.0)
 
Effectiveness and relative effectiveness of recombinant and standard dose influenza vaccines against RT-PCR confirmed influenza for non-immunocompromised adults 18–64 years old, excluding recipients of other advanced (non-RIV4) vaccines
Influenza
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) 40 (22, 54) 1 (−38, 28) 2 (−37, 31) −8 (−56, 25) −2 (−41, 27)  
Age 18–49 years 47 (27, 61) 51 (28, 67) −11 (−77, 30) 2 (−61, 40) −5 (−71, 35) −6 (−71, 35)  
Age 50–64 years 29 (3, 48) 28 (−4, 50) 10 (−41, 42) 5 (−53, 41) −1 (−64, 38) −8 (−74, 34)  
Female sex 37 (18, 51) 34 (9, 52) 1 (−47, 32) 5 (−42, 37) −6 (−62, 31) −5 (−58, 30)  
Male sex 46 (18, 65) 49 (21, 68) 2 (−76, 45) −13 (−121, 42) −11 (−121, 45) −6 (−100, 43)  
High-risk condition 42 (25, 56) 21 (−15, 46) 28 (−11, 53) 29 (−11, 55) 26 (−21, 55) 28 (−15, 55)  
No high-risk condition 31 (1, 52) 55 (34, 69) −53 (−153, 7) −67 (−185, 2) −66 (−193, 6) −61 (−174, 5)  
2018–2019 season 43 (15, 62) 47 (20, 65) −7 (−83, 37) −5 (−84, 40) −13 (−113, 40) −9 (−98, 41)  
2019–2020 season 38 (20, 52) 37 (11, 55) 2 (−48, 35) 0 (−55, 35) −15 (−85, 28) −7 (−67, 32)  

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.

Standard dose = All standard dose egg-based; excludes other advanced (non-RIV4) vaccines Propensity score: Generalized Boosted Regression Method was used to calculate the propensity score using TWANG (Toolkit for Weighting and Analysis of Nonequivalent Groups).