Sex-specific effects of aging on the humoral immune response to repeat vaccination with the
1
high-dose seasonal influenza vaccine in older adults
2
3
Janna R. Shapiro
1
, Huifen Li
2
, Rosemary Morgan
1
, Yiyin Chen
3
, Helen Kuo
1
, Xiaoxuan Ning
4
,
4
Patrick Shea
5
, Cunjin Wu
6
, Katherine Merport
7
, Rayna Saldanha
7
, Suifeng Liu
8
, Engle Abrams
2
,
5
Yan Chen
9
, Denise C. Kelly
2
, Eileen Sheridan-Malone
2
, Lan Wang
10
, Scott L. Zeger
11
, Sabra L.
6
Klein
1,5*
, and Sean X. Leng
2,5*
7
8
1
Department of International Health, Johns Hopkins Bloomberg School of Public Health,
9
Baltimore, MD, USA.
10
2
Division of Geriatric Medicine and Gerontology, Department of Medicine, Johns Hopkins
11
University School of Medicine, Baltimore, MD, USA.
12
3
Guangdong Geriatrics Institute, Guangdong Provincial People’s Hospital, Guangdong Academy
13
of Medical Sciences, Guangzhou, Guangdong, China.
14
4
Department of Geriatrics, Xijing Hospital, The Fourth Military Medical University, Xi’an,
15
Shaanxi, China.
16
5
W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins
17
Bloomberg School of Public Health, Baltimore, MD, USA.
18
6
Department of Geriatrics, The Second Hospital of Tianjin Medical University, Tianjin, Hebei,
19
China.
20
7
Zanvyl Krieger School of Arts and Science, Johns Hopkins University, Baltimore, MD, USA.
21
8
Zhongshan Hospital, Xiamen University, Xiamen, Fujian, China.
22
9
Department of Geriatrics, The First Affiliated Hospital of Chongqing Medical University,
23
Chongqing, Sichuan, China.
24
10
Department of Geriatrics, The First Affiliated Hospital, Zhejiang University School of Medicine,
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Hangzhou, Zhejiang, China
26
11
Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore,
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MD, USA.
28
*
Corresponding authors
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30
Running title: Age, sex, and humoral immunity to influenza
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Key words: age, sex difference, HAI antibody titer, influenza vaccination
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Manuscript statistics:
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Abstract: 172 words
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Main text: 4,818 words
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Figure: 5
36
Tables: 4
37
References: 70
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Contact information: Address correspondence to Sabra Klein (sklein2@jhu.edu) or Sean Leng
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(sleng1@jhmi.edu)
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(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
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NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice.
Shapiro et al.
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Abstract
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Older adults (≥65 years of age) bear a significant burden of severe disease and mortality
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associated with influenza, despite relatively high annual vaccination coverage and substantial
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pre-existing immunity to influenza. To test the hypothesis that host factors, including age and
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sex, play a role in determining the effect of repeat vaccination and levels of pre-existing
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humoral immunity to influenza, we evaluated pre- and post-vaccination strain-specific
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hemagglutination inhibition (HAI) titers in adults over 75 years of age who received a high-dose
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influenza vaccine in at least four out of six influenza seasons (NCT02200276). Neither age, sex,
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body mass index, frailty, nor repeat vaccination were significantly associated with post-
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vaccination HAI titer outcomes. Pre-vaccination titers, however, were significantly predictive of
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post-vaccination outcomes. Pre-vaccination titers to H1N1 remained constant with age, while
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those to H3N2 and influenza B decreased substantially with age in males but not in females.
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Our findings highlight the importance of pre-existing immunity in this highly vaccinated older
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adult population and suggest that older males are particularly vulnerable to reduced pre-
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existing humoral immunity to influenza from previous annual vaccination.
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(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprintthis version posted July 23, 2021. ; https://doi.org/10.1101/2021.07.21.21260712doi: medRxiv preprint
Shapiro et al.
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Introduction
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Seasonal influenza is an important public health burden in older adults (people ≥65
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years of age), particularly the oldest and frail subset
1-3
. In the United States (U.S.), there are an
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estimated 4 million incident cases per year in older adults, accounting for 90% of deaths
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associated with influenza
4,5
. The U.S. Centers for Disease Control and Prevention (CDC)
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recommends annual influenza vaccination for prevention of influenza infection and
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complications in people 6 months and older
6
. The high-dose inactivated influenza vaccine (HD-
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IIV) is available to older adults and has demonstrated superior efficacy over standard-dose
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vaccines in this vulnerable age group
6,7
. Seasonal influenza vaccine coverage is relatively high in
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older adults, with >60% of older Americans vaccinated annually, compared to <40% of the 18-
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49 age group
8
.
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Age-related immunosenescence, defined by a decline in cellular and humoral immune
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function combined with a chronic low-grade inflammatory phenotype (CLIP)
9-11
, is believed to
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be the primary reason for the reduced effectiveness of influenza vaccines observed in older
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adults
12-14
. Repeated annual vaccination may also have a negative effect on vaccine-induced
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humoral immune responses as well as vaccine effectiveness (VE). For example, a recent
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observational test-negative study using ten years of vaccination history found that in older
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adults, VE decreased with increasing numbers of previous vaccinations but that vaccination
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continued to offer some level of protection
15
. Another study over eight seasons in the general
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adult population found that VE to H3N2, but not influenza B, was reduced among individuals
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with frequent vaccination history compared to those without prior vaccination
16
. The impact of
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repeat vaccination on H3N2 was confirmed by a meta-analysis, which found heterogeneous
79
All rights reserved. No reuse allowed without permission.
(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprintthis version posted July 23, 2021. ; https://doi.org/10.1101/2021.07.21.21260712doi: medRxiv preprint
Shapiro et al.
4
effects of repeat vaccination overall; however, when negative effects were observed, they were
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most pronounced for H3N2
17
. In contrast, a recent systematic review and meta-analysis
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concluded that the available evidence does not support a reduction in VE with consecutive
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repeat vaccination, but that certainty in the evidence was low
18
. Case control studies in both
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Australia and Spain found beneficial effects of repeated annual vaccination on VE in older
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adults
19,20
, and an observational population-based study in Sweden found no differences in VE
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between those who had been vaccinated in the current season only and those who had been
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vaccinated in both the current and previous seasons
21
. Based on the conflicting evidence,
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multi-season clinical studies to address the effects of aging and repeated vaccination have been
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recommended
17
.
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Mechanistically, pre-existing immunity generated to various influenza virus exposures
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over time can have an important impact on the outcome of vaccination. According to immune
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imprinting theory, the memory response established by an individual’s first influenza exposure
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has a lifelong effect on subsequent immune responses to infection or vaccination
22
. Broad pre-
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existing immunity is thought to have negative consequences, as pre-existing antibodies can
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suppress the response to novel influenza virus strains by reducing the amount of available
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antigen or epitope masking
23,24
. A theoretical benefit of HD-IIV is that pre-existing antibodies
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cannot sequester the increased amount of antigen delivered, and, thus, more antigen is
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available to activate memory B cells and elicit a protective response
25-27
. To our knowledge,
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however, the impact of pre-existing immunity in the context of the HD-IIV has not been
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adequately characterized.
100
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(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprintthis version posted July 23, 2021. ; https://doi.org/10.1101/2021.07.21.21260712doi: medRxiv preprint
Shapiro et al.
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In addition to age, other host factors including sex, frailty, and body mass index (BMI)
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can impact vaccine responses in older adults. Females have been found to mount greater
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antibody responses to HD-IIV than males
28
. The relationship between frailty and influenza
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vaccine responses is debated in the literature, with one study reporting frailty having a negative
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effect
29
, others reporting no effect
30-34
, and others still reporting a positive effect
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. Finally, in
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older adults, obesity is significantly associated with decreased hemagglutination inhibition (HAI)
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titers and percentage of switched memory B cells
36
. We hypothesize that the variation across
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studies in estimates of the effects of pre-existing immunity and repeat annual vaccination is
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partly caused by failure to adequately account for heterogeneity and interactions among host
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factors that likely differ across studies. To address this knowledge gap, we used a longitudinal
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cohort of older adults over 75 years of age who had received high-dose, trivalent inactivated
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influenza vaccine (HD-IIV3) in at least four out of six influenza seasons to estimate the impact of
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repeat vaccination on the antibody response to HD-IIV3 and its dependence on the intersection
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of age, sex, frailty, BMI, pre-existing immunity.
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Results
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Study Participants and annual influenza immunization with HD-IIV3
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Over the six influenza seasons from 2014-2015 to 2019-2020, 90 individuals participated
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in at least four study seasons and 433 doses of HD-IIV3 were. The strains included in each
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vaccine and the study protocol are described in Figure 1. Table 1 shows demographic and
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clinical characteristics of the study participants. There was a slight predominance of females
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(55.6%), and yearly study enrollment increased over time. Baseline characteristics, measured
122
All rights reserved. No reuse allowed without permission.
(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprintthis version posted July 23, 2021. ; https://doi.org/10.1101/2021.07.21.21260712doi: medRxiv preprint
