A phase 1 randomized controlled trial of an experimental intranasal vaccine against multiple H5N1 avian flu strains generated a broad immune response in US adults, researchers reported today in Nature Communications.

The findings come the same day as the Mexican Ministry of Health reported the death of a 3-year-old Durango girl from H5N1 infection, highlighting the need for prevention.

Intramuscular influenza vaccines mainly trigger systemic immune responses that protect against symptomatic illness when well-matched to circulating strains. But they may be less effective at preventing person-to-person transmission than intranasal vaccines, which stimulate immunity at the infection site.

Potential role in pandemic preparedness

For the study, University of Maryland investigators randomly assigned 40 adults aged 18 to 45 to receive either NanoVax’s adjuvanted, recombinant intranasal influenza A/H5 vaccine or a placebo from July 2022 to October 2023.