A new intranasal vaccine developed by researchers at Washington University School of Medicine in St. Louis demonstrates significant protection against the highly pathogenic H5N1 bird flu virus. Unlike traditional injectable vaccines, this formulation is administered directly through the nose, triggering robust immune responses and effectively preventing infection in animal models. This approach addresses a critical gap in current bird flu preparedness, especially given the recent and unexpected jump of H5N1 into U.S. dairy cows, raising concerns about a potential pandemic.
The Challenge of Existing Vaccines
Current bird flu vaccines are often outdated, designed for older viral strains, and may not effectively combat the latest H5N1 variants. Widespread availability is also limited. The WashU team built on existing nasal vaccine technology – previously used in a COVID-19 vaccine approved in India and undergoing U.S. clinical trials – to create a more responsive and accessible alternative.
How the Vaccine Works
The vaccine employs a precise antigen design, selecting proteins from H5N1 strains known to infect humans. This antigen is delivered via a harmless adenovirus, effectively training the immune system to recognize and neutralize the virus. The delivery method mimics the approach used in the COVID-19 nasal vaccine, ensuring efficient activation of immune defenses.
Superior Protection in Animal Studies
Testing in hamsters and mice revealed near-complete protection against H5N1 infection with the nasal vaccine. In contrast, animals with prior seasonal flu immunity showed little defense against the bird flu virus. Importantly, the nasal spray consistently outperformed traditional intramuscular injections, even at low doses and under high viral exposure.
The vaccine generated strong immune responses throughout the body, with particularly high activity in the nasal passages and respiratory tract, the primary entry points for infection. This targeted approach offers a significant advantage over injected vaccines by providing better protection where it’s needed most.
Overcoming Prior Immunity
A key advantage of this vaccine is its effectiveness even in individuals with existing immunity from previous flu infections or vaccinations. This is critical, as most people have some level of prior immune memory, making it a practical solution for real-world deployment.
Future Development
The research team plans further animal studies and testing on human tissue models to refine the vaccine. Ongoing efforts focus on minimizing interference from prior seasonal flu immunity and maximizing antiviral responses.
“Delivering vaccine directly to the upper airway where you most need protection from respiratory infection could disrupt the cycle of infection and transmission. That’s crucial to slowing the spread of infection for H5N1 as well as other flu strains and respiratory infections.” – Michael S. Diamond, MD, PhD
The development of this nasal vaccine represents a substantial step forward in bird flu preparedness, offering a potentially more effective and accessible solution to prevent infection and limit transmission.
