WashU Medicine Develops Promising Nasal Vaccine for H5N1 Bird Flu
Researchers at Washington University School of Medicine in St. Louis (WashU Medicine) have developed an innovative nasal vaccine targeting the highly pathogenic H5N1 avian influenza virus, commonly known as bird flu. This vaccine demonstrated a strong immune response and effectively prevented infections in rodents exposed to H5N1.
The Looming Threat of H5N1 Bird Flu
The H5N1 avian influenza virus has been present in the U.S. since 2014, making concerning jumps from wild birds to livestock, and subsequently to humans. Since 2022, the U.S. has reported over 70 human cases, tragically including two fatalities.
The virus's continued circulation among animal populations raises significant global health concerns about its potential to evolve human-to-human transmissibility and trigger a widespread pandemic.
Developing the Intranasal Solution
The new intranasal vaccine leverages existing nasal vaccine technology previously developed by WashU Medicine for a COVID-19 vaccine. Researchers Jacco Boon, PhD, and Eva-Maria Strauch, PhD, meticulously selected specific H5N1 proteins representative of circulating strains that had infected humans to create an optimal antigen. This antigen was then integrated into a harmless, non-replicating adenovirus, which serves as the efficient delivery vehicle.
Comprehensive testing in hamsters and mice showed the vaccine provided near-complete protection against H5N1 infection. In stark contrast, current seasonal influenza vaccines offered only minimal protection.
The nasal spray vaccine proved more effective in protecting against H5N1 infection than the same formula administered through traditional intramuscular immunization.
Notably, strong protection was observed even when the nasal vaccine was given as a low dose against a high exposure to bird flu.
Benefits of Nasal Administration
Nasal delivery of the vaccine elicited a robust immune response throughout the entire body, with a particularly strong localized effect in the nose and respiratory tract.
Researchers noted that this method offers superior protection against infection in the nose and lungs, which could reduce transmission in addition to preventing severe disease.
The study also addressed a critical practical concern: whether existing immunity from other flu vaccines or prior infections would negatively impact the H5N1 vaccine's performance. Results conclusively indicated that the nasal vaccine still provided strong protection, even in the presence of pre-existing immunity—a vital feature given that most individuals have prior immune experiences with influenza.
Next steps for the research team include conducting additional studies in animals and organoids representing human immune tissue. They also plan to develop new vaccine versions aimed at further minimizing the effects of prior seasonal influenza infection and promoting even greater antiviral responses.
The promising findings were officially published on January 30 in the esteemed journal Cell Reports Medicine.