AZ vaccine candidate works better given nasally, animal study shows
doi:10.1038/nindia.2021.69 Published online 12 May 2021
A new study involving the University of Oxford-AstraZeneca COVID-19 vaccine in ferrets shows that nasal delivery, instead of the current intramuscular administration, might potentially improve the vaccine’s effectiveness1.
The ‘ChAdOx1 nCoV-19’ vaccine, known as ‘Covishield’ in India and ‘AZD1222’ in other parts of the world, was found to induce effective immune responses in ferrets (Mustela putorius furo) and reduce viral load in nasal-wash and oral swab samples. The study was carried out by scientists at Australia’s science agency the Commonwealth Scientific and Industrial Research Organisation with funding from the Coalition for Epidemic Preparedness Innovations (CEPI).
According to the researchers, only 2 out of 8 animals that received prime-boost intranasal administration had detectable viral RNA in nasal-wash and oral swab samples three days after getting the dose as compared to 6 out of 8 animals via the intramuscular route. They suggest the potential for intranasal administration as a way to further improve the efficacy of this leading vaccine candidate.
“There was no detectable viral RNA in any of the wash or swab samples for animals in the intranasal group on subsequent days,” the authors say. They add, however, that reduction in viral shedding following intranasal administration warrants further clinical investigation.
The Australian study was the first to investigate if giving the vaccine through the nose would confer additional protection due to mucosal immunity. "The lower serum neutralising titres measured in animals that received intranasally administered ChAdOx1 nCoV-19 compared to intramuscular administration can likely be explained through the induction of a more localised mucosal immune response compared to the systemic response induced by peripheral inoculation, as previously demonstrated with influenza vaccines," the authors say.
If the results from ferrets are confirmed in humans, it could help improve the vaccine’s reported overall efficacy, the authors contend.
1. Marsh, G. A. et al. ChAdOx1 nCoV-19 (AZD1222) vaccine candidate significantly reduces SARS-CoV-2 shedding in ferrets. npj Vaccines doi: 10.1038/s41541-021-00315-6 (2021)