The Effect of Influenza Vaccination History on Changes in Hemagglutination Inhibition Titers After Receipt of the 2015–2016 Influenza Vaccine in Older Adults in Hong Kong

Abstract

Background Immune responses to influenza vaccination can be weaker in older adults than in other age groups. We hypothesized that antibody responses would be particularly weak among repeat vaccinees when the current and prior season vaccine components are the same. Methods An observational study was conducted among 827 older adults (aged ≥75 years) in Hong Kong. Serum samples were collected immediately before and 1 month after receipt of the 2015–2016 quadrivalent inactivated influenza vaccine. We measured antibody titers with the hemagglutination inhibition assay and compared the mean fold rise from prevaccination to postvaccination titers and the proportions with postvaccination titers ≥40 or ≥160. Results Participants who reported receipt of vaccination during either of the previous 2 years had a lower mean fold rise against all strains than with those who did not. Mean fold rises for A(H3N2) and B/Yamagata were particularly weak after repeated vaccination with the same vaccine strain, but we did not generally find significant differences in the proportions of participants with postvaccination titers ≥40 and ≥160. Conclusions Overall, we found that reduced antibody responses in repeat vaccinees were particularly reduced among older adults who had received vaccination against the same strains in preceding years.

Seroprevalence of influenza viruses in Shandong, Northern China during the COVID-19 pandemic

“…A total of 475 potentially relevant articles were retrieved after systematic search, of which 12 met all the inclusion criteria (Fig. 1B) [2][3][4][5][17][18][19][20][21][22][23][24]. A total of 9656 individuals were included in our metaanalysis (Table S1).…”

Vaccine- and natural infection-induced mechanisms that could modulate vaccine safety

“…a virus or bacterium) is encountered.) [ [105] , [106] , [107] , [108] ]; Prior Influenza Infection/Vaccination (effects of prior influenza infection/vaccination on severity of future disease symptoms) [ [109] , [110] , [111] , [112] , [113] , [114] , [115] , [116] ]; Timing between Viral Exposures (elapsed time between viral exposures) [ [117] , [118] , [119] , [120] ]; Vaccine-Associated Enhanced Respiratory Disease (where vaccination enhances respiratory disease) [ [121] , [122] , [123] ]; Chronic Immune Activation (continuous innate immune responses) [ [124] , [125] , [126] ]. …”

“…Prior Influenza Infection/Vaccination (effects of prior influenza infection/vaccination on severity of future disease symptoms) [ [109] , [110] , [111] , [112] , [113] , [114] , [115] , [116] ];…”

Antibody Responsiveness to Influenza: What Drives It?

“…After repeated influenza vaccination, the serological response to recent vaccination may decrease. Repeat-influenza vaccination can result in higher baseline titers and lower magnitude fold changes, particularly when the vaccine strains were unchanged [126,127]. Importantly, reduced immunogenicity after repeated vaccination did not appear to be associated with reduced protection [128], likely because seroprotective titers were already present or protection was mediated by non-HAI-antibodies.…”