Influenza Immunoglobulin for Adults Hospitalized with Influenza
123 Pages Posted: 5 Apr 2019More...
Background: Despite treatment with licensed antiviral agents, high rates of influenza-related morbidity and mortality occur worldwide.
Methods: Adults hospitalized with laboratory-confirmed influenza were randomized (1:1) to a single double-blind infusion of high-titer anti-influenza intravenous immunoglobulin (hIVIG) or saline placebo. The primary endpoint was an ordered categorical outcome, ranging in severity from death to post-discharge resumption of normal activities, assessed at Day 7. The odds ratio (OR) (hIVIG versus placebo) of a favorable outcome was estimated with a proportional odds model.
Findings: Of 308 randomized patients, 73% and 27% had influenza A and B, respectively; antiviral use was 95%. As expected, hIVIG produced a robust rise in influenza A hemagglutination inhibition (HAI) titers, and smaller rises in influenza B titers. Viral load declined after 3 days by 1.99 (hIVIG) versus 2.32 log10 copies/mL (placebo) (p=0.49). The OR for favorable outcome was 1.25 (95% confidence interval [CI] 0.79-1.97, p=0.33). ORs for influenza A and B were 0.94 (95% CI: 0.55-1.59) and 3.19 (95% CI: 1.21-8.42), respectively (p=0.02 for difference). This difference between influenza A and B was mirrored for secondary clinical outcomes, changes in viral load, and in sensitivity analyses, overall and by strain. To investigate this outcome further, anti-HA antibody affinities were measured in the hIVIG lots administered, and much stronger antibody affinities for B strains were observed than for A in hIVIG used.
Interpretation: Overall, hIVIG was not superior to placebo for adults hospitalized with influenza. In contrast to our pre-study subgroup hypothesis based upon conventional HAI titers in hIVIG, benefit was evident for those with influenza B but not A. Consistent with findings of a contemporaneous anti-influenza plasma trial (IRC005), adjunctive immunotherapy appears ineffective for severe influenza A. The beneficial effect of hIVIG for influenza B is supported by antibody affinity analyses, but confirmation of clinical benefit is warranted.
Clinical Trial Registration: ClinicalTrials.gov Identifier: NCT02287467.
Funding: NIAID, NIH.
Declaration of Interest: There are no competing interests to declare in regard to this manuscript submission.
Ethical Approval: The trial was approved by the institutional review board or ethics committee for each clinical site. All patients provided written informed consent.
Keywords: immunotherapy, influenza, intravenous immunoglobulin
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