Anti-Influenza Hyperimmune Immune Globulin Not Effective in Hospitalized Adults with Influenza Infection

Encouraged by nonrandomized studies and small clinical trials suggesting convalescent plasma or anti-influenza hyperimmune intravenous immune globulin (hIVIG) might have clinical benefit, a multinational team conducted a randomized, double-blind, placebo-controlled trial to assess the safety and efficacy of hIVIG (in conjunction with standard care) in adults hospitalized with laboratory-confirmed influenza A or B infection.

Patients were eligible if they had a National Early Warning (NEW) score of 2 points or greater at the time of screening, onset of symptoms no more than seven days before randomization, and were expected to be hospitalized more than 24 hours. The investigational hIVIG product was manufactured using high-titer antiinfluenza plasma collected either from fractionated whole blood or by plasmapheresis from U.S. and Canadian volunteers. Donors and plasma units were selected on the basis of increased hemagglutination inhibition antibody titers against contemporary vaccine strains.

In 308 patients enrolled in 34 sites between December 2014 and May 2018, hIVIG treatment produced a robust rise in hemagglutination inhibition titers against influenza A, and smaller rises in influenza B titers. Through 28 days of follow-up, 47 (30 percent) of 156 patients in the hIVIG group and 45 (30 percent) of 152 patients in the placebo group had the composite safety outcome of death, a serious adverse event or a grade 3 or 4 adverse event (hazard ratio 1.06, 95% confidence interval, 0.70-1.60; p=0.79).

On the basis of the primary ordinal outcome of clinical status at day seven (ranging in severity from death to post-discharge resumption of normal activities), hIVIG was not superior to placebo for adults hospitalized with influenza infection. In contrast with a negative finding in patients with influenza A, antibody affinity analyses identified a clinical benefit for patients with influenza B, but confirmation is warranted with a further randomized controlled trial.