US researchers say a single nasal spray vaccine could protect against coughs, colds and flu. The vaccine could also prevent bacterial lung infections and may even reduce allergies. Scientists at Stanford University tested the universal vaccine in animals and still need human clinical trials. They describe the approach as a radical break from more than 200 years of vaccine development. Experts called the findings exciting but emphasized that the research remains at an early stage.
Conventional Vaccines Protect Against Only One Infection
Current vaccines train the immune system to fight a single infection. A measles vaccine protects against measles, and a chickenpox vaccine protects against chickenpox. This approach has guided immunisation since Edward Jenner pioneered vaccines in the late 18th century. The new method follows a completely different concept.
Immune Cells Are Placed on Constant Alert
The new approach does not train the immune system in the traditional way. Instead, it mimics how immune cells communicate with each other. The nasal spray leaves white blood cells in the lungs, called macrophages, on alert. These cells stand ready to respond to any invading infection. Animal experiments showed the effect lasted around three months.
Dramatic Reduction in Viruses Reaching the Lungs
The researchers reported a 100-to-1,000-fold reduction in viruses passing through the lungs. The rest of the immune system reacted quickly to any viruses that slipped through. Prof Bali Pulendran said the immune system could fight intruders at extreme speed. The team also showed protection against Staphylococcus aureus and Acinetobacter baumannii bacteria.
Broad Protection Against Viruses, Bacteria and Allergens
Pulendran said the vaccine triggered a broad protective response. He said it worked against flu viruses, Covid viruses, common cold viruses and many tested bacteria. He added that it could even protect against allergens. He described the principle as a radical break from existing vaccine strategies. The immune response also reduced reactions to house dust mite allergens that trigger asthma.
Experts Highlight Major Potential
Prof Daniela Ferreira from the University of Oxford described the research as exciting. She said it could transform protection against respiratory infections if human studies confirm the results. She highlighted the clear explanation of how the vaccine works. Ferreira said the findings could mark a major step forward against infections that place a heavy burden on people worldwide.
Unanswered Questions Before Human Trials
Scientists still need to answer many questions before clinical use. The vaccine was given as a nasal spray in animals, but humans may need a nebuliser to reach deeper lung regions. Researchers do not know if the same effect will occur in people or how long it will last. Human immune systems differ from mice and are shaped by decades of infections. The team plans trials where vaccinated volunteers are deliberately exposed to infections to study their immune response.
Warnings About Overactive Immune System
Experts warn that increasing immune alert levels could cause unintended side effects. Jonathan Ball from the Liverpool School of Tropical Medicine urged caution about friendly fire reactions. He said a hyper-ready immune system could trigger harmful immune responses. The research team said the immune system should not stay permanently activated. They believe the vaccine should complement existing vaccines rather than replace them.
Potential Role During Pandemics and Seasonal Illnesses
Researchers said a universal vaccine could buy time during the early stages of a pandemic. It could reduce deaths and disease severity while specialised vaccines are developed. Pulendran said it could build broader immune resilience with huge impact. He also suggested a seasonal spray at the start of winter to provide broad immunity against circulating respiratory viruses.
