COVID-19 nasal vaccines are available but should you get one?
The Centre has given its nod to Bharat Biotech's nasal vaccine: iNCOVACC. It has been included in the COVID-19 vaccination program and has been approved to be used as a heterologous booster from today. But the burning concerns are whether nasal vaccines are efficacious and whether they can help curb the transmission of the COVID-19 virus. Let's take a look.
Why does this story matter?
iNCOVACC is the first nasal vaccine in India to be approved by the government. There are more than 100 mucosal vaccines that are being developed across the world. The needle-free vaccines might also help overcome the reluctance among certain parts of the population who refrain from getting jabs. Given the promising results of nasal vaccines, they could be a game-changer.
First, what are nasal vaccines?
Nasal vaccines, as the name suggests, are administered via the nose as opposed to the most commonly used intramuscular route. These vaccines offer several advantages compared to traditional vaccination approaches such as convenience, ease of delivery, cost, and disposal. Furthermore, several studies report that intranasal administration of COVID-19 vaccines can prevent disease development as well as limit the transmission of the virus.
How do nasal vaccines work?
Nasal vaccines target mucous membranes lining the nose, mouth, and lungs. The mechanism by which they work is that nasal vaccines act as the "first entry block" and produce immune responses where the pathogen first enters the body. This subsequently prevents the infection and curbs the spread to other people, something which the current intramuscular vaccines cannot do.
Tissue-resident memory cells produce immunoglobulin A antibodies
The immune cells in the mucosal linings are referred to as tissue-resident memory T and B cells and they function differently from the T cells and B cells that are in circulation. The tissue-resident memory B cells produce antibodies called secretory immunoglobulin A (or IgA), which are also predominantly present in external secretions, including mucus in the digestive tract, saliva, and tears.
The IgA antibodies can entrap and block pathogens
IgA has various functions in mucosal defense, including entrapping pathogens and preventing them from direct contact with the mucosal surface and thereby blocking them. However, a more pressing concern is the evolving variants of the COVID-19 virus, which have the potential to evade or suppress the immune system, and a changed route of administration does not address this issue.
