New Delhi: An intranasal version of the AstraZeneca Covid vaccine has been found to prevent infection and lower viral shedding in animals, a result that may pave the way for an improved vaccine that also prevents Covid transmission.
The study suggests that intranasal Covid-19 vaccines may be better able to control the replication of SARS-CoV-2 virus in the nasal cavity.
While the intramuscular AstraZeneca Covid vaccine, ChAdOx1, is being widely used across the world — it is available in India as Covishield — and has been found to be effective in preventing severe infection and deaths, previous studies in monkeys have shown that it does not reduce shedding of SARS-CoV-2 from the upper respiratory tract, according to researchers of this study.
For the study, published Wednesday in the journal Science Translational Medicine, researchers, including those from the University of Oxford, administered the ChAdOx1 vaccine intranasally to hamsters and monkeys.
They found that the vaccine generated antibodies and protected the animals from SARS-CoV-2 infection. But along with this, the vaccine also lowered viral shedding and viral loads in nasal swab samples from the hamsters more effectively than an intramuscular injection.
The study comes just a day after CanSino shared Phase 1 trials results of its inhaled vaccine, which showed that the vaccine was safe for human use.
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Checking the spread
It is currently unclear whether the detection of virus in nasal swabs translates directly to transmissibility in humans after infection.
This means that if a vaccinated individual gets Covid, though the person may not be severely ill, the SARS-CoV-2 virus might still be replicating in the upper respiratory system — which includes the nose, nasal cavity, and the throat — and be transmitted to other individuals.
Currently, the majority of Covid-19 vaccines in development utilise an intramuscular (IM) injection, which tends to yield poorer immune responses in mucosal tissues, which contain some components of the immune system. Mucosal tissues are strategically located tissues in areas from where pathogens enter the body, such as the nose, mouth and throat. These tissues have plasma cells that make up an important part of the immune system known as mucosal immunity.
When vaccines are injected through intramuscular injection, this part of the immune system gets ignored or does not get activated. For a vaccine to elicit mucosal immunity, antigens will need to be encountered at the initial site where the virus replicates — the upper respiratory tract.
“To address this, we evaluated the potential of using the Covid-19 vaccine candidate, ChAdOx1 nCoV-19, as an intranasal vaccine in hamster and rhesus macaque models,” researchers wrote in the study.
The researchers said that they are now conducting a phase 1 clinical trial to test the intranasal vaccine with 54 healthy adults.
(Edited by Poulomi Banerjee)
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