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Inhaled vaccines may be a better alternative than nasal sprays, study finds

Experts say inhaled vaccines travel farther into the respiratory system to offer stronger protection

Medical concept with lungs
Photo (c) mi-viri - Getty Images
A new study conducted by researchers from McMasters University explored the effectiveness of different types of vaccines delivered through the respiratory system. Their findings showed that inhaled vaccines are likely to reach deeper into the respiratory system, which makes them more effective than nasal spray vaccines. 

“Infections in the upper respiratory tract tend to be non-severe,” said researcher Matthew Miller. “In the context of infections caused by viruses like influenza or SARS-CoV-2, it tends to be when the virus gets deep into the lung that it makes you really sick. 

“The immune response you generate when you deliver the vaccine deep into the lung is much stronger than when you only deposit that material in the nose and throat because of the anatomy and nature of the tissue and the immune cells that are available to respond are very different.”  

Better protection from viruses

The researchers put different types of vaccines to the test on animals. They used both an inhaled and nasal spray tuberculosis vaccine and compared the immune responses, general potency of the vaccines, and the distribution of droplets in the animals. 

While both vaccines proved to be effective, the inhaled vaccine provided a much stronger immune response. The researchers explained that the nasal spray vaccine travels to the nose and throat but doesn’t go much further than that in the body. 

The study showed that the inhaled tuberculosis vaccine was more effective because it was able to reach deeper into the respiratory system. With the inhaled vaccine, the immune droplets never settled in the nasal passages. Instead, they traveled farther into the lungs. 

The researchers are currently in the middle of clinical trials that are testing an inhaled COVID-19 vaccine that would work in this way by targeting the respiratory system. 

“This study for the first time provides strong preclinical evidence to support the development of inhaled aerosol delivery over nasal spray for human vaccination against respiratory infections including TB, COVID-19, and influenza,” said researcher Zhou Xing. 

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