The story so far: On September 6, Union Health Minister Mansukh Mandaviya tweeted that the Central Drugs Standard Control Organisation had approved Bharat Biotech’s nasal vaccine for primary immunisation against COVID-19 in the 18-plus age group for restricted use in an emergency situation. It is hoped that Bharat Biotech’s ChAd36-SARS-CoV-S recombinant vaccine, to be administered nasally and developed in association with the University of Washington, will prove a powerful tool in the battle against the virus by preventing infections, something the other vaccines have not been able to do.
What does the vaccine do?
A nasal vaccine is delivered through the nose or mouth and it is expected to work on the mucosal lining, prompting an immune response at the entry points of the virus in the human body. It likely prevents the infection right there, thereby also blocking its spread. Scientists have called this sterilising immunity, where the virus is prevented from causing infection in the host effectively.
Early studies at Washington University, according to a report published on the varsity’s website, “showed that nasal delivery of this vaccine creates a strong immune response throughout the body, especially in the nose and respiratory tract. In animal studies, the nasal vaccine prevented infection from taking hold in the body.”
Emily Waltz explains in an article in Nature, that the COVID-19 vaccines currently in use do a good job of reducing disease severity and preventing hospitalisation, but don’t block mild illness or transmission that well. The reason for that is that they are injected into the muscle. “Intramuscular shots prompt an immune response that includes T cells, which destroy infected cells, and B cells, which produce antibodies that ‘neutralise’ pathogens — binding to them to stop them entering healthy cells. These cells and antibodies circulate through the bloodstream. But they aren’t present at high enough levels in the nose and lungs to provide rapid protection. In the time it takes for them to journey there from the bloodstream, the virus spreads, and the infected person gets ill.”
Is a nasal vaccine the best defence against COVID-19 so far?
“Exactly how successful these vaccines will be is unclear. Expecting a vaccine to stop transmission of a virus or prevent even mild illness — achieving what is called sterilising immunity — is a high bar. Bharat [Biotech] and CanSino [Chinese vaccine maker that has secured a licence to use another nasal vaccine] won’t know whether their vaccines can achieve this until they have conducted further efficacy studies,” explains Ms. Waltz.
Both Bharat Biotech and CanSino have announced that their trials have been successful but have not released data. She points to two other nasal vaccines that have reportedly been deployed in populations, one in Iran and the other, an intra-nasal version of Sputnik V in Russia, but says scant data is available from either of them.
In a release, Bharat Biotech said: “The product — iNCOVACC — is stable at 2-8°C for easy storage and distribution. The reactogenic events and adverse events that were documented during the trial were highly comparable to the published data from other COVID-19 vaccines. Product development data will be submitted to peer-reviewed journals and will be made available in the public domain.”
The University of Washington article indicated that two clinical trials of the nasal vaccine were conducted in India. “A phase 3 trial involving about 3,100 previously unvaccinated people who received two doses of the nasal vaccine, and a booster trial with about 875 people who received a single dose of the nasal vaccine after two doses of another COVID-19 vaccine. These trials, which concluded in August, indicated that the vaccine is safe and effective at eliciting a strong immune response in people when used either as a primary vaccine or as a booster.”
Early publication of trial data and a speedy rollout of a nasal vaccine would be ideal. By avoiding the jab, the nasal vaccine might be more appealing to people not yet vaccinated. It can be an option for children too, for whom it has not been authorised for use yet. Also, though two vaccines were authorised for use in the 5-12 and 6-12 age groups in April, there is no sign of a rollout for these candidates.