Immunogenicity of H5N1 influenza vaccines in elderly adults: a systematic review and meta-analysis

Abstract

Several different vaccines have been produced for human use to prevent the highly pathogenic H5N1 influenza. Some studies reported that the clinical effectiveness of influenza vaccines in older adults may be lower than in younger adults. In this study, a meta-analysis of the immunogenicity of H5N1 influenza vaccines in elderly adults was performed. Database search was conducted in EMBASE, PubMed, the Cochrane Library, Chinese VIP, Wanfang and CBM. A total of 3951 elderly adults from 10 articles were included in the meta-analysis. Compared to a single dose, two doses of H5N1 vaccines resulted in the higher seroconversion and seroprotection. For all groups treated with adjuvanted vaccines, there were significant increases (1.55- to 2.16-fold) in the seroconversion rates (SCRs) and seroprotection rates (SPRs) after two immunizations. Oil-in-water emulsion (OE)-adjuvanted 7.5 μg vaccine caused higher antibody responses than 3.75 μg of vaccine (SCR: risk ratio (RR) = 1.26 (1.19, 1.33); SPR: RR = 1.25 (1.14, 1.36)). Elderly adults exhibited slightly lower antibody responses only when given 7.5 μg of OE-adjuvanted vaccine (SCR: RR = 1.06 (1.01, 1.11)) than younger adults. After treatment with the 7.5 μg of OE-adjuvanted vaccines, the most commonly reported adverse events were injection site pain, swelling and erythema, with the incidence of 32%, 3% and 2%, respectively, and no serious adverse events were found. These data demonstrate that two doses of 7.5 µg of OE-adjuvanted H5N1 vaccine are well tolerated and induce a robust antibody response in elderly adults.

Immunological and clinical efficacy of COVID-19 vaccines in immunocompromised populations: a systematic review

“…Risk factors for non-response status often included older age, which is consistent with data provided by phase 1 and 2 studies of COVID-19 vaccines [ 191 , 192 ], as well as in other vaccines such as influenza, pneumococcal and hepatitis B vaccines [ [202] , [203] , [204] , [205] ]. Immunosuppressive therapy and biological agents, especially B-cell depleting agents, often negatively impact immune responses to COVID-19 vaccines.…”

Precision Vaccine Adjuvants for Older Adults: A Scoping Review

“…In a meta-analysis of 16 studies evaluating real-world vaccine effectiveness (VE) in adults ≥65Y, the MF59-adjuvanted vaccine demonstrated significant absolute VE and improved relative VE for the prevention of influenza-related medical encounters compared with nonadjuvanted trivalent (pooled estimate of +13.9%) and quadrivalent (pooled estimate of +13.7%) influenza vaccines [ 17 ]. AS03-adjuvanted influenza vaccine also induced robust Ab responses, whereas modest Ab responses were evident after receipt of alum-adjuvanted H5N1 influenza vaccine [ 18 ]. Several systematic reviews and meta-analyses have focused on safety in older adults, with the most comprehensive one demonstrating significantly increased risk of local AEs following MF59- and AS03-adjuvanted vaccines compared with control vaccines.…”

“…Encouraging preclinical and clinical data support a growing pipeline of novel adjuvants tailored to older adults [ 31 ]. In contrast, our review indicated that the conventional alum adjuvant did not consistently enhance humoral immune responses in older adults when evaluated in pneumococcal, RSV, influenza, and Clostridium difficile vaccines, which highlights the need for new adjuvants that are active in older adults [ 10 , 18 , 37–39 ].…”

Substantial effect of phytochemical constituents against the pandemic disease influenza—a review

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