Scientists at NIAID’s Vaccine Research Center (VRC) report in two new studies that an experimental influenza vaccine, designed to elicit immunity against a broad range of influenza viruses, performed well in a small trial of volunteers. In fact, the vaccine has advanced to a second trial led by scientists at Duke University through NIAID’s Collaborative Influenza Vaccine Innovation Centers (CIVICs).

In a phase 1 clinical trial of 52 volunteers, the vaccine developed by the VRC – known as H1ssF (influenza H1 hemagglutinin stabilized stem ferritin nanoparticle vaccine) – was safe, well-tolerated, and induced broad antibody responses that target the hemagglutinin stem. The two new studies assessing the nanoparticle vaccine published April 19 in Science Translational Medicine.

Healthy volunteers ages 18-70 enrolled at the NIH’s Clinical Center and were given either a single 20-microgram dose or two 60-microgram vaccine doses. Boosters were given 16 weeks after the initial dose. The trial enrolled between April 1, 2019, and March 9, 2020.

Trial participants did not experience any severe adverse events; the most common vaccine reactions included mild headache, tenderness at the vaccine site, and temporary general discomfort.

As anticipated based on preclinical study results, H1ssF generated binding antibodies to the stem of the influenza H1 hemagglutinin (HA) protein. Antibody responses were observed regardless of dose or participant age. “These responses were durable, with neutralizing antibodies observed over one year after vaccination,” the authors stated, suggesting this vaccine prototype can advance further universal influenza vaccine development.

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