American scientists are developing a new nasal spray vaccine that could potentially protect the body against all types of influenza, the common cold, bacterial lung infections, and even certain allergies, reports BBC.

Researchers at Stanford University have already tested their “universal vaccine” in animals and are now preparing to conduct human trials.

They say their approach differs radically from traditional vaccines, which have been used for more than 200 years. Experts in the field describe the findings as truly impressive, although the research is still at an early stage. They hope the vaccine could represent a major breakthrough in combating disease.

Current vaccines “train” the body to fight one specific infection. For example, a measles vaccine protects only against measles, just as a chickenpox vaccine targets only that virus. This has been the principle of immunization since it was first introduced in the late 18th century by British physician Edward Jenner.

However, the approach described by the authors in the journal Science does not aim to train the immune system to recognize a particular pathogen. Instead, it mimics the way immune cells communicate with one another.

The vaccine is administered as a nasal spray, which leaves white blood cells in the lungs — known as macrophages — in a state of readiness for activation. As a result, they respond regardless of which specific infection attempts to enter the body.

In animal experiments, the vaccine’s effect lasted about three months. The study showed that the heightened readiness of macrophages significantly reduced the number of viruses entering the body through the lungs — by 100 to 1,000 times fewer viral particles.

“The immune system is fully primed to respond instantly to any viruses that do manage to get through,” said Professor Bali Pulendran, professor of microbiology and immunology at Stanford University.

The research team also found that the new vaccine helped protect against two bacterial species — Staphylococcus aureus and Acinetobacter baumannii — which are responsible for several hospital-acquired infections.

“This vaccine, which we call universal, triggers a much broader immune response and protects not only against influenza, not only against COVID, not only against the common cold, but practically against all viruses and many different bacteria, as we have shown experimentally — and even against allergies,” Pulendran told the BBC.

Changes in immune system function also appear to reduce its reaction to allergens found in dust, which can trigger allergic asthma.

“This is a truly impressive study,” said Professor Daniela Ferreira, a vaccinology expert at the University of Oxford, who was not involved in the Stanford research.

According to her, the work “could change the way we protect people from colds and other respiratory infections” if the results are confirmed in human trials. She added that one strength of the research is the clear explanation of how the vaccine works.

However, many questions remain. In animal experiments, the vaccine was delivered as a nasal spray, but in humans it may require nebulizers to ensure it reaches the lungs effectively.

It is still unknown whether the human body will respond in the same way or how long the immune system would remain in this heightened state. Human and mouse immune systems differ significantly, partly because human immunity develops through decades of exposure to infections.

Researchers now hope to conduct trials in which volunteers receive the vaccine and are then exposed to a virus to assess the immune response. There are also concerns that maintaining the immune system in a more active state could potentially cause unintended immune-related side effects.

Professor Jonathan Ball, professor of molecular virology at the Liverpool School of Tropical Medicine, called the work highly impressive but cautioned: “We need to be sure that keeping the immune system on ‘high alert’ does not result in friendly fire, where an overactive immune response causes unwanted side effects.”

The American researchers emphasize that their vaccine is not intended to replace existing vaccines but rather to complement them.

In the early stages of a pandemic — such as at the beginning of the global spread of COVID-19 in 2020 — a universal vaccine could buy time while a pathogen-specific vaccine is being developed.

“It could reduce mortality, make the disease less severe, and likely create immune resilience — the ability to recover quickly. The impact could be very significant,” Pulendran said.

He also suggested another possible application: at the beginning of winter, as seasonal viruses spread, “one could imagine using such a seasonal spray to create broader immunity.”