An inhaled COVID-19 vaccine developed by CanSino Biologics has entered late-stage clinical trials, with data suggesting it is eligible to apply for emergency use in China, the company's chief scientist said.

Zhu Tao, a member of the Chinese People's Political Consultative Conference National Committee, said future COVID-19 vaccination may replace the "jab" with a "huff", and the procedure is as simple as "sipping a cup of coffee".

The recipient takes a deep breath from a cup containing the aerosol of the vaccine, holds the gas for around five seconds, and slowly breathes out. The whole process takes around 10 seconds and is completely painless, making it ideal for individuals who are scared of needles, he said.

Zhu said clinical data shows that the inhaled vaccine is safe and can deliver broad protection against the novel coronavirus that causes COVID-19, including its mutated strains.

As respiratory viruses typically target the lungs and upper airways, an inhaled vaccine can bolster the immune response in cells that form the mucous membrane in those parts of the body, serving as the first line of defense against the pathogen, Zhu said.

"This respiratory mucosal protection is a property that is lacked by vaccines delivered through intramuscular injection," he said.

Studies have shown that one of the key reasons behind the Omicron variant's high transmissibility is that it is very efficient at infecting the upper respiratory tract, so a person taking an inhaled vaccine would be better protected against that kind of virus, Zhu added.

In addition, inhaled vaccines require a lower dosage to elicit an immune response, he said.

The inhaled vaccine being researched by CanSino is based on its Convidecia adenovirus vector vaccine for COVID-19, which has been approved for use in more than 10 countries, including China, Pakistan, Mexico, Chile, Indonesia and Malaysia.

"The inhaled version only uses about one-fifth of the dosage of a conventional injection," Zhu said, making it much easier to administer and more accessible to people around the globe.

With these advantages, some experts around the world believe that an inhaled vaccine could be a game changer in the global battle against COVID-19.

Researchers in the United States, Canada, the United Kingdom, India and Japan are also developing inhaled or nasal spray COVID-19 vaccines designed to fight the virus in the upper airways, according to the World Health Organization.

However, while inhaled medicine has been widely used to treat asthma and other respiratory diseases, inhaled vaccines are a relatively new technology, and not all vaccines can be huffed, Zhu said.

For example, vaccines that require aluminum-containing adjuvants, a common ingredient to help vaccines induce a stronger immune response, are not suitable because the adjuvants cannot be atomized into tiny particles with diameters less than 5 micrometers, or five-thousandths of a millimeter.

"If the particle is too big, it is unsafe to breathe into the respiratory tract," Zhu said.

"The vaccine also cannot contain any form of solid particles. Overall, making a safe and effective inhalable vaccine is much harder than traditional ones."