A nasal version of the Oxford/AstraZeneca Covid-19 vaccine has failed in an early-stage trial, dealing a blow to hopes for a more effective way to prevent transmission of the virus.
Oxford university said on Tuesday a nasal formulation of the vaccine elicited mucosal antibody responses in a “minority of participants” and systemic immune responses were also weaker compared with intramuscular vaccination.
The setback highlights the complexity of designing a nasal formulation against coronavirus, which spreads through tiny particles in the air. Researchers have posited that targeting the airways could effectively prevent transmission of the disease. Currently available vaccines, delivered as intramuscular injections, only offer limited protection against contagion, although they retain significant effectiveness against more severe outcomes.
Oxford’s Sandy Douglas, chief investigator on the trial, said the spray, which used the same formulation as the intramuscular version of the vaccine, did not perform as well as researchers had hoped.
“We believe that delivery of vaccines to the nose and lungs remains a promising approach, but this study suggests there are likely to be challenges in making nasal sprays a reliable option,” said Douglas. He said it was possibly because the majority of the spray ended up being swallowed and destroyed in the stomach, although targeted delivery into the lungs could avoid that.
Oxford said a possibility for the future would be to develop formulations made specially for nasal administration, for example with higher concentrations or elements that help the spray stick in the upper airways rather than being swallowed.
There were no adverse events or safety concerns reported in the phase 1 study, which also explored administering the spray as a booster.
There are more than a dozen Covid-19 nasal vaccine candidates currently in trials. China recently approved a nebulised Covid-19 vaccine made by CanSino, although the delivery mechanism was slightly more complex. India recently approved an intranasal vaccine made by Bharat Biotech.
AstraZeneca, Oxford’s partner for the Covid-19 vaccine, funded the study.