While most of the 160 Covid-19 vaccine candidates under various stages of development are conventional intramuscular injection, several research groups and firms, including in the United States, Canada and India, are working on nasal coronavirus vaccines. Instead of a jab into the upper arm, these types of vaccines will be delivered to the respiratory tract, either via a nasal spray or aerosol delivery.
Since coronavirus is a respiratory infection and invades the airway, scientists from the UK’s Oxford University and Imperial College and US’ Yale University have said administering a vaccine at the entry points would train the mucosa to identify Covid-19 and block it from getting through. Scientists have identified two specific types of cells in the nose as the likely initial infection points for SARS-CoV2.
Mucous membranes are squishy tissues that line the surfaces of internal organs like lungs and respiratory tract and catch pathogens that try to get into the body.
“The hope is that mucosal vaccines will do all that their intramuscular competitors can and more, mounting a multi pronged attack on the coronavirus from the moment it tries to breach the body’s barriers,” the New York Times quoted Deepta Bhattacharya, an immunologist at the University of Arizona, as saying.
What is a nasal/mucosal vaccine?
Intranasal vaccines are delivered to the respiratory tract, spritzed through the nose or mouth, to target the immune cells that are found around the mucosal tissues. While an intramuscular vaccination mainly induces an antibody response, a nasal vaccination is beneficial as it triggers mucosal, as well as systemic immunity. Moreover, intranasal vaccination may also offer protection at other mucosal sites such as the lungs, intestines and genital tract.
How will Covid-19 nasal vaccines work?
T cells and B cells are the major cellular components of the body’s immune response. In normal circumstances, upon vaccination, B cells would provide antibodies — called IgG — to search for pathogens. Other cells, called T cells, either helps B cells produce antibodies or seek out and destroy infected cells.
In case of intranasal vaccination, the B cells that reside around mucosal tissues can make another type of antibody — called IgA — that plays a large role in heeling gut and airway pathogens. Nearby T cells can then memorise the features of specific pathogens and patrol the places they first encountered them.
Which firms are working on developing a nasal Covid-19 vaccine?
At present, five firms in the US, Canada, the Netherlands, Finland and India are working on developing a nasal vaccine to cure Covid-19.
Canadian vaccine candidate: Researchers at the University of Waterloo in Canada are developing a DNA-based vaccine candidate that can be given via nasal route. For the vaccine, the scientists are using the bacteriophage-based approach. This will allow the vaccine to stimulate an immune response in the nasal cavity and target tissues in the lower respiratory tract.
Intravacc: Dutch research and development vaccine institute Intravacc, Wageningen Bioveterinary Research (WBVR) and Utrecht University are jointly developing an intranasal vaccine. According to a statement by Intravacc, the vaccine candidate contains a Newcastle disease virus (NDV) vector that expresses the novel coronavirus’ immunogenic spike protein, a key target for neutralising antibodies. The company stated that NDV demonstrated safety for intranasal delivery in mammals, including primates.
AdCOVID: Biopharmaceutical firm Altimmune, in collaboration with DynPort Vaccine, has developed a intranasal Covid-19 vaccine candidate, AdCOVID. In pre-clinical studies, the experimental vaccine has shown strong serum neutralising activity besides potent mucosal immunity in the respiratory tract. The company expects to start manufacturing during the third quarter of this year.
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Finland nasal spray: Researchers at the University of Eastern Finland and the University of Helsinki are developing a Covid-19 vaccine that will be administered as a nasal spray using gene transfer technology. Professor Seppo Ylä-Herttula has told the media that clinical trials would begin in autumn. The vaccine, based on an adenovirus carrier, will contain genetic information on how to produce coronavirus surface protein in humans. The administration of the vaccine into the nose and upper respiratory tract will start the formation of antibodies against the virus.
CoroFlu: Besides Covaxin, Bharat Biotech, in collaboration with University of Wisconsin–Madison and vaccine firm FluGen, has also developed ‘CoroFlu’, a one-drop Covid-19 nasal vaccine. ‘CoroFlu’ will likely undergo human clinical trials by the fall of 2020. ‘CoroFlu’ has been developed on the backbone of FluGen’s existing flu vaccine candidate M2SR, which is a self-limiting version of the influenza virus that induces an immune response against the flu.
How have scientists reacted?
The voice behind the possible benefits of an intranasal vaccine for Covid-19 gained traction after Professor Robin Shattock, an immunologist at Imperial College London, told the House of Commons Science and Technology Committee that a second wave of studies looking into mucosal immunisation should be carried out, a report in The Daily Mail said.
Sarah Gilbert, professor of vaccinology at Oxford University, also said that oral or nasal vaccination would have much stronger mucosal response. “This takes the vaccine itself right down into the lungs where it can access the same tissue that would be reached by the virus infection,” she said. However, she had a word of caution also, saying that delivering a vaccine through the nose “is actually getting very close to the brain”. “Putting it down into the lungs, you’re exposing a very large surface area to the new entity,” she further said.
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