Factors associated with humoral immune response in older adults who received egg-free influenza vaccine. Issue 3 (16th January 2023)

• Record Type: Journal Article
• Authors: Williams, Katherine V.; Moehling Geffel, Krissy; Alcorn, John F.; Patricia Nowalk, Mary; Levine, Min Z.; Kim, Sara S.; Flannery, Brendan; Susick, Michael; Zimmerman, Richard K.
• Is Part Of: Vaccine. Volume 41:Issue 3(2023)
• Page Start: 862
• Page End: 869
• Publication Date: 2023-01-16
• Subjects: Influenza -- Egg-free influenza vaccine -- Hemagglutination inhibition assay -- Adults -- Humoral response; Vaccines -- Periodicals; 615.372
• DOI: 10.1016/j.vaccine.2022.12.041
• Languages: English
• ISSNs: 0264-410X

Abstract

Highlights: Age and baseline HAI titers were associated with immune response to egg-free influenza vaccine. HAI response differed by antigen level contained in prior season's influenza vaccine. The ideal sequence of vaccine formulations across influenza seasons remains unknown. Abstract: Background: Immune responses to influenza vaccination tend to be lower among older, frequently vaccinated adults. Use of egg-free influenza vaccines is increasing, but limited data exist on factors associated with their immunogenicity in older adults. Methods: Community-dwelling older adults ≥ 56 years of age were enrolled in a prospective, observational study of immunogenicity of 2018–2019 influenza vaccine. Hemagglutination inhibition (HAI) antibody titers were measured pre-vaccination (Day 0) and four weeks after vaccination (Day 28) to calculate geometric mean titers, seropositivity (HAI titers ≥ 1:40), seroconversion (fourfold rise in HAI titer with post-vaccination titer ≥ 1:40) and geometric mean fold rise (GMFR). Linear regression models assessed the association of predictors of GMFR for each vaccine antigen. Results: Among 91 participants who received egg-free influenza vaccines, 84 (92.3 %) received quadrivalent recombinant influenza vaccine (RIV4, Flublok, Sanofi Pasteur), and 7 (7.7 %) received quadrivalent cell culture-based influenza vaccine (ccIIV4, Flucelvax, Seqirus). Pre-vaccination seropositivity was 52.8 % for A(H1N1), 94.5 % for A(H3N2), 61.5 % for B/Colorado and 48.4 % for B/Phuket. Seroconversion by antigen ranged from 16.5 % for A(H1N1) and B/Colorado to 37.4 % for A(H3N2); 40 participants failed to seroconvert to any antigen. Factors independently associated with higher GMFR in multivariable models included lower pre-vaccination HAI antibody titer for A(H1N1), B/Colorado and B/Phuket, and younger age for A(H1N1). Conclusion: Overall pre-vaccination seropositivity was high and just over half of the cohort seroconverted to ≥ 1 vaccine antigen. Antibody responses were highest among participants with lower pre-vaccination titers. Among older adults with high pre-existing antibody titers, approaches to improve immune responses are needed.