An intranasal vaccine, as the name suggests, is administered via the nose, and doesn’t require a needle. Basically, it works by making the nasal mucus, which is the first line of defense against airborne infections like Covid19, more efficient. As one article reads, “[Intra-nasal vaccines] aim to stop Covid19 where it starts.”

At present, while aerosolized vaccines have not completed trials for Covid19 yet, they already exist for diseases like influenza in humans, and kennel cough in dogs.

The novel coronavirus gains entry into human bodies through the nostrils, where it comes into contact with the mucosal membranes that line our airways — besides our digestive and reproductive tracts. “When you think about it, that’s where we acquire most of our infections: we inhale them, we consume them, or we get them through sex,” said Michael W. Russell, a mucosal immunologist and professor emeritus at the University at Buffalo.

Underneath the mucous membranes, there lies a network of immune cells that make up the mucosal immune system, which “prevent[s] most infections from taking root” by “form[ing] a front line of defense” against invading pathogens. But Russell believes immunologists have been underestimating it while researching potential ways to curb the spread of Covid19. “When the pandemic hit last year and I started to see papers coming out about immunity, it really quite staggered me to see an absence of attention to the mucosal immune response,” he added.

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So far, experts believe intranasal vaccines may have some advantages over intramuscular ones. As Indian Express explained, not only do intranasal vaccines involve smaller quantities than intramuscular ones, but they also don’t require trained healthcare workers to administer the doses.

“Indeed intra-nasal vaccines will be far easier to deliver than intramuscular injections [and] Asha workers can be trained to deliver it at a mass scale unlike IM injections which will need nurses, doctors [and] MBBS students which is a challenge,” Kiran Mazumdar-Shaw, who heads Biocon, an Indian biotechnology company, tweeted.

Some scientists also believe that while intramuscular vaccines are certainly effective at preventing severe disease and death, they may not be as effective at blocking the infection itself as an intra-nasal vaccine can be.

“The whole medical community has been so fixated on injected vaccines that a lot of people just don’t seem to be able to think beyond that. And clearly, they work in the majority of cases, there is no arguing with that… But the immune system doesn’t depend on having stuff injected. There are other ways of going about it,” Russell noted.

For Indians especially, non intramuscular vaccines are hardly news, given how widespread the orally administered polio vaccine is in India.

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Researchers from Wuhan in China have completed Phase I trials of an aerosolized vaccine on 130 human participants. Their results suggested that people who received them experienced fewer adverse effects compared to people who were administered intramuscular vaccines. The most common adverse effects reported within seven days of being vaccinated were fever, fatigue, and headache, and no serious adverse events were detected for up to 56 days after the first vaccine.

In terms of the antibody responses, the researchers noted it was two doses of the aerosolized vaccine were equivalent to one dose of intramuscular one.

An intra-nasal version of the AstraZeneca vaccine — known in India as Covishield — has been trialed in hamsters and monkeys. The findings show that it was able to lower viral shedding — or, the spread of viral particles by infected, asymptomatic individuals) — too.

India, too, has approved Bharat Biotech’s request this month to conduct human trials for an intra-nasal vaccine the company has developed.

Currently, more than five intranasal vaccines are being trialed by different countries across the globe.