Inhaled vaccines better than nasal sprays, study proves

Researchers have proved through a new study that inhaled vaccines are much better than nasal sprays and this is because nasal sprays reach primarily the nose and throat while on the other hand inhaled aerosols bypass the nasal passage and deliver vaccine droplets deep in the airway thereby triggering broad protective immune response.

For the study, published online in the journal Frontiers in Immunology, the researchers used a tuberculosis vaccine to compare delivery methods by measuring the distribution of droplets, immune responses and potency in animals. When the vaccine was delivered directly into the lungs it stimulated stronger immune responses, providing much better protection from TB.

Scientists take the example of viruses like influenza or SARS-CoV-2 and point out that they tend go deep in the lungs and make the patient very sick. The immune response generated when vaccine is delivered deep into the lung is much stronger than when the material is only deposited 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.

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.

Scientists at McMaster, who have developed a unique inhaled form of COVID vaccine, believe this deep-delivery method offers the best defence against the current and future pandemics.

A Phase 1 clinical trial is currently under way to evaluate the inhaled aerosol vaccine in healthy adults who had previously received two or three doses of an injected COVID mRNA vaccine.

Nasal mist flu vaccines have been shown to be highly effective in children, but much less effective in adults, leaving injectable flu vaccines as the most popular choice for seasonal flu vaccinations.

Previous research by the McMaster team has shown that in addition to being needle-free and painless, an inhaled vaccine is so efficient at targeting the lungs and upper airways that it can achieve maximum protection with a much smaller dose than injected vaccines.

The research was funded by the Canadian Institutes for Health Research and the Natural Sciences and Engineering Research Council of Canada.