Nasal Spray H5N1 Vaccine Shows Near-Complete Protection in Early Animal Studies
核心洞察
Researchers at Washington University School of Medicine developed a nasal spray vaccine (搜索) for H5N1 (搜索) bird flu (搜索) that provided near-complete protection against infection in hamsters and mice.
The nasal vaccine generated stronger immune responses and better protection than traditional intramuscular vaccines, particularly in preventing infection in the nose and lungs where flu viruses first establish themselves.
The vaccine remained effective even in animals with pre-existing immunity from prior flu exposure, addressing a key concern for practical deployment.
Researchers at Washington University School of Medicine have developed a promising nasal spray vaccine (搜索) for H5N1 (搜索) bird flu (搜索) that demonstrated near-complete protection against infection in early animal studies, offering new hope for pandemic preparedness as the virus continues to spread among animals and humans.
The intranasal vaccine (搜索), tested in hamsters and mice, generated strong immune responses throughout the body, particularly in the nose and respiratory tract where flu viruses first infect and replicate. According to findings published in Cell Reports Medicine, the nasal delivery provided superior protection compared to the same vaccine formula administered through traditional intramuscular injection.
Superior Protection Against Infection and Transmission
"Delivering vaccine directly to the upper airway where you most need protection from respiratory infection could disrupt the cycle of infection and transmission," said Dr. Michael Diamond, Professor of Molecular Microbiology at Washington University and co-senior author of the study. "That's crucial to slowing the spread of infection for H5N1 (搜索) as well as other flu strains and respiratory infections."
The nasal vaccine's advantage lies in its ability to stimulate mucosal immunity in the nose and airways, stopping viruses from establishing themselves at their primary infection sites. While traditional flu vaccines delivered by injection are highly effective at preventing serious illness, there remains a 40 to 60 percent chance that vaccinated individuals can become infected and silently transmit the virus to others.
The research team found that nasal vaccines respond to features shared across all strains rather than targeting a single variant, making them better suited to rapidly changing viruses and requiring less frequent updates to remain effective.
Addressing Pre-existing Immunity Concerns
A critical finding was that the vaccine maintained strong protection even in animals with pre-existing immunity from prior flu exposure. This addresses a significant concern, as pre-existing immunity from seasonal influenza (搜索) infection or vaccination could potentially diminish H5N1 (搜索) vaccine efficacy.
"We've shown that this nasal vaccine delivery platform we conceived, designed and conducted initial testing on at WashU Medicine (搜索) can prevent H5N1 (搜索) infection from taking hold in the nose and lungs," Diamond noted.
Growing Pandemic Threat
The vaccine development comes as H5N1 (搜索) continues to pose an escalating pandemic threat. Since 2022, at least 70 people in the US have contracted the virus, mostly after close contact with infected animals, with two fatalities reported. The virus has become endemic in US dairy cattle and was recently detected in European cows in the Netherlands for the first time.
"This particular version of bird flu (搜索) has been around for some time, but the unique and totally unexpected event where it jumped across species into dairy cows in the United States was a clear sign that we should prepare for the event that a pandemic may occur," said Dr. Jacco Boon, Professor at WashU Medicine (搜索) and co-senior author of the study.
Since October alone, more than nine million birds have been culled following farm outbreaks in the US, Canada, and Europe. Scientists warn that the growing number of cases increases opportunities for the virus to mutate and potentially gain the ability to spread between humans—a scenario the World Health Organization calls an "enormous concern."
Limitations of Current Vaccines
Existing H5N1 (搜索) vaccines were developed to match older virus strains from the mid-2000s and are poorly matched to newer, rapidly mutating strains that have spread widely since 2020. Some estimates suggest their effectiveness could be as low as 45 percent against current variants.
The virus historically carries a very high case fatality rate: of nearly 900 people who have contracted H5N1 (搜索) since the late 1990s, nearly half have died.
Next Steps and Development Timeline
The vaccine's development remains in early stages and will require rigorous testing in humans through multiple phases of clinical trials before potential rollout—a process that typically takes years. The researchers plan to conduct additional studies in animals and organoids representing human immune tissue, while developing new versions that further minimize effects of prior seasonal influenza (搜索) infection and promote greater antiviral responses.
The nasal vaccine technology builds on a platform previously developed at Washington University, with a COVID-19 vaccine based on their approach already available in India since 2022 and approved for clinical testing in the US last year.