Interseason waning of vaccine-induced hemagglutination inhibition antibody titers and contributing factors to pre-existing humoral immunity against influenza in community-dwelling older adults 75 years and older

Table 4 Independent effects of interseason antibody waning and prior season post-vaccination HAI antibody titers on current season pre-vaccination HAI titers^a

		Model 1^b Interseason titer waning		Model 2^c Prior season post-vaccination titers
Vaccine Strain	Consecutive two seasons	Adjusted for prior season post-vaccination titers	Adjusted for additional covariates^c	Adjusted for interseason antibody waning	Adjusted for additional covariates^c
IAV-H3N2	2014–2015 (n = 49)	1.06 (1.04–1.08) (p < .01)	1.06 (1.04–1.08)(p < .01)	1.82 (1.65–1.99) (p < .01)	1.83 (1.67–2.01) (p < .01)
IAV-H3N2	2015–2016 (n = 52)	1.21 (1.18–1.24) (p < .01)	1.21 (1.18–1.24) (p < .01)	1.98 (1.90–2.07) (p < .01)	1.98 (1.90–2.07) (p < .01)
IBV	2014–2015 (n = 49)	1.27 (1.22–1.31) (p < .01)	1.26 (1.22–1.31) (p < .01)	2.04 (1.94–2.13) (p < .01)	2.04 (1.95–2.14) (p < .01)
IBV	2015–2016 (n = 52)	1.16 (1.14–1.18) (p < .01)	1.16 (1.14–1.18) (p < .01)	2.02 (1.94–2.10) (p < .01)	2.02 (1.94–2.11) (p < .01)
IAV-H1N1	2016–2017 (n = 78)	1.17 (1.15–1.19) (p < .01)	1.17 (1.14–1.19) (p < .01)	1.91 (1.81–2.00) (p < .01)	1.92 (1.82–2.03) (p < .01)

^aSummary of estimated effects of interseason antibody waning adjusting for prior season post-vaccination HAI antibody titers (Model 1) and vice versa (Model 2) on current season pre-vaccination HAI antibody titers. Notes: Outcome measure is current season pre-vaccination HAI antibody titers measured using prior season vaccine strain antigens
^bEstimated effects are expressed as expected fold-change (95% confidence interval) in current season pre-vaccination HAI titers that is associated with a 0.1-unit less interseason antibody waning after adjusting against prior season post-vaccination HAI antibody titers (Model 1) or a two-fold increase in prior season post vaccination HAI antibody titers after adjusting against interseason antibody waning (Model 2), with or without adjusting for additional covariates (both Model 1 and 2)
^cAdditional covariates include age at prior study season, sex, race, and education

ISSN: 1742-4933