- Two immunologists say an intranasal Covid vaccine can elicit an immune response at the site of infection – the respiratory tract.
- Intranasal vaccination, which is administered through the nose, is also needle-free, meaning that more people may be willing to get vaccinated.
- Ultimately, using both intramuscular and intranasal Covid vaccines may be effective in combating Covid-19.
Out of the 108 Covid-19 vaccines that are currently undergoing clinical trials, only eight are delivered intranasally (through the nose) – the rest are mainly given intramuscularly (into the muscle).
Considering SARS-CoV-2, the respiratory virus that causes Covid-19, predominantly enters the nasal passage first (this is why testing for the virus involves nasal swabs), a nasal spray vaccine could be beneficial in the continued fight against Covid, say two immunologists from the University of Alabama at Birmingham (UAB).
Writing in a viewpoint article, published in the journal Science, they explain that a spray vaccine would, therefore, attack the virus at the site of infection before it has the chance to move deeper into the body.
According to an article published in The Conversation, needle phobia could be the cause of 10% of Covid vaccine hesitancy in the UK alone, while another noted that 25% of Americans are averse to needles. New research indicates that people who are afraid of needles are twice as likely to be vaccine-hesitant.
And the fact that they're administered without needles is one of the great advantages of intranasal vaccines, said the authors.
Intranasal vaccines have also long been successful in providing protection against the influenza (flu) virus. “The idea that intranasal vaccination preferentially protects the respiratory tract is not new: Development of the US Food and Drug Administration (FDA)–approved live attenuated influenza vaccine (LAIV) began in the 1960s,” they explained.
Few intranasal vaccines in trials
There are also two additional layers of protection that an intranasal vaccine can give over the intramuscular vaccine, said the researchers. This is because it produces:
- Immunoglobulin A (an antibody) and resident memory B and T cells in the mucous membrane lining the respiratory tract – an effective barrier to infection at those sites
- Cross-reactive resident memory B and T cells that can respond earlier than other immune cells, if a viral variant starts an infection
“Given the respiratory tropism of the virus, it seems surprising that only seven of the nearly 100 SARS-CoV-2 vaccines currently in clinical trials are delivered intranasally,” co-authors Dr Fran Lund, and Dr Troy Randal said in a news release.
“Advantages of intranasal vaccines include needle-free administration, delivery of antigen to the site of infection, and the elicitation of mucosal immunity in the respiratory tract,” they added.
In their viewpoint, they also go on to detail the individual advantages and challenges of each of the intranasal vaccine candidates. (Seven were undergoing trials at the time their article was published.)
'All hands on deck approach'
Commenting on the researchers' article in a tweet, Joint Managing Director of the Apollo Hospitals Group, Dr Sangita Reddy said: “Given their remarkable allure to block Covid-19 transmission, we do need on priority an all hands on deck approach to manufacturing.”
Using both vaccines
After comparing the benefits and disadvantages of intranasal vaccination to intramuscular vaccinations, the authors concluded that effective vaccination need not be restricted to a single route.
The ideal vaccination strategy, they said, may use an intramuscular vaccine initially, followed by an intranasal booster shot, which could then lead to a strong immune response elicited both locally and systemically.
“Thus, intranasal vaccines may have to balance the goal of local immunity in the respiratory tract with the longevity of systemic immunity,” they wrote.