Stanford develops nasal spray vaccine that protects against multiple viruses

A universal vaccine could fight colds and flu

Researchers at Stanford University have developed a nasal spray vaccine that, in animal studies, protected against a wide range of viruses, bacteria, and even allergens. The approach represents a fundamental shift from how vaccines have worked for over two centuries.

Current vaccines train the immune system to recognize and fight one specific pathogen. The new method, detailed in the journal Science, instead puts the lungs' frontline immune cells into a heightened state of general readiness.

How the new vaccine works

The vaccine is administered as a nasal spray. It leaves white blood cells in the lungs, called macrophages, on "amber alert." This means they are primed to jump into action against virtually any invader that tries to enter through the respiratory tract.

In experiments on mice, this effect lasted for about three months. It led to a 100-to-1,000-fold reduction in the amount of virus that could penetrate from the lungs into the body.

"The rest of the immune system was poised, ready to fend off these in warp speed time," said senior author Prof Bali Pulendran, a professor of microbiology and immunology at Stanford.

Broad protection against multiple threats

The team showed the vaccine provided protection not just against flu and common cold viruses, but also against two species of antibiotic-resistant bacteria: Staphylococcus aureus and Acinetobacter baumannii.

It also appeared to reduce the immune system's response to house dust mite allergens, a common trigger for allergic asthma. Pulendran told the BBC the vaccine works against "virtually all viruses, and as many different bacteria as we've tested."

Key aspects of the vaccine's mechanism and tested protections include:

• It mimics immune cell communication instead of targeting a single germ.
• It reduced viral load in lungs by 100 to 1,000 times in mice.
• It protected against multiple viruses and two drug-resistant bacteria.
• It moderated allergic responses to common triggers like dust mites.

Experts call it a potential major step

Independent experts in the field, while noting the early stage of the research, described the study as highly promising. Prof Daniela Ferreira, a professor of vaccinology at the University of Oxford, called it a "really exciting piece of research."

"It could change how we protect people from common coughs, colds and other respiratory infections," she said, if the results hold in human trials. She added the work "could mark a major step forward" against infections that place a heavy burden on society.

Significant questions remain before human use

Major hurdles must be cleared before this could become a usable product. It is unknown if the same powerful effect can be achieved in humans, whose immune systems are more complex and shaped by a lifetime of prior infections.

The researchers plan initial human challenge trials, where a vaccinated person is deliberately exposed to a pathogen to test the response. The method of delivery may also need to change from a simple nasal spray to a nebulizer to ensure it reaches deep into human lungs.

There is also a critical safety question about keeping the immune system in a prolonged state of high alert. Prof Jonathan Ball of the Liverpool School of Tropical Medicine cautioned, "we have to ensure that keeping the body on high alert doesn't lead to friendly fire, where a hyper-ready immune system accidentally triggers unwelcome side effects."

Envisioned as a complement to existing vaccines

The Stanford team does not envision this as a permanent replacement for current vaccines. Instead, they see it as a complementary tool for specific situations.

One scenario is at the start of a pandemic, like COVID-19 in early 2020, where a universal vaccine could buy critical time and save lives while a pathogen-specific vaccine is developed. Another is a seasonal spray at the start of winter to provide broad protection against circulating respiratory bugs.

"That would reduce mortality, disease severity, and perhaps build up a level of immune resilience that would have a huge impact," said Pulendran.