NIH-led phase 1 trial finds experimental universal flu vaccine BPL-1357 well tolerated

A peer-reviewed phase 1 trial published in Nature Communications on 12 October 2026 reports that BPL-1357, an experimental whole-virus “universal” influenza vaccine developed with NIH intramural support, was generally well tolerated and immunogenic in healthy adults — especially when given by intramuscular (IM) injection.

Study design

Forty-five healthy participants were randomized to IM BPL-1357, intranasal (IN) BPL-1357 or placebo, with a prime and a boost 28 days apart (NCT05027932). The vaccine contains four wild-type, low-pathogenicity avian influenza viruses inactivated with beta-propiolactone. Primary endpoints were adverse and serious adverse events through 28 days after the boost; secondary endpoints included longer safety follow-up and serum IgG / nasal IgA titers.

Main results

Side effects were mostly mild; mild injection-site pain was more common in the IM group. IM vaccination raised serum IgG to H3, H5 and H7 versus placebo, with response rates of 71.4%, 71.4% and 85.7% of participants respectively, plus neutralizing and neuraminidase-specific serum responses. IM dosing did not induce mucosal IgA to HA or NA. IN dosing produced only subtle mucosal and serum responses.

Limitations

This is an early safety and immunogenicity study in a small healthy cohort — not a test of protection against influenza infection or disease. Dose finding, broader immune characterization and efficacy trials are still needed. The article is not medical advice; talk to your doctor about flu vaccination.