A seasonal nasal spray that vaccinates against Covid is to be tried on patients having returned positive results in lab tests.
The spray targets mucous membranes – moist inner linings of organs or cavities that produce phlegm – and is much better at preventing spread than muscle jabs, say the Berlin team behind it.
‘Nasal vaccines are far more effective in this regard than injected vaccines – which fail or struggle to reach the mucous membranes,’ said co-author Dr Emanuel Wyler, of the Max Delbruck Centre in Germany.
When infected people speak, cough, sneeze or laugh they expel droplets of saliva containing the virus. Others catch the bug by breathing in airborne pathogens which take hold in the nose, mouth, throat and lungs.
Dr Wyler and colleagues developed a weakened form of SARS-CoV-2, the virus that causes Covid, that is administered through the nose.
Trials in humans are already being planned – with potential benefits going far beyond providing a nasal pump as an alternative for those afraid of needles.
When a vaccine is injected it infers immunity primarily in the blood and throughout the entire body. This means the immune system only detects and combats coronaviruses relatively late on in an infection – as they enter the body via the mucous membranes of the upper respiratory tract.
Co-author Dr Jakob Trimpert, of Freie University, said: ‘It’s here, therefore, that we need local immunity if we want to intercept a respiratory virus early on.’
Ideally a nasal vaccine directly stimulates antibodies in the mucous membranes – preventing infection from occurring in the first place.
‘Memory T cells that reside in lung tissue play a similarly useful role to antibodies in the mucosa,’ said co-author Dr Geraldine Nouailles, from Charite University Hospital.
‘These white blood cells remain in affected tissue long after an infection has passed and remember pathogens they have encountered before. Thanks to their location in the lungs, they can respond quickly to viruses that enter through the airways.
‘We were able to show prior intranasal vaccination results in the increased reactivation of these local memory cells in the event of a subsequent SARS-CoV-2 infection. Needless to say, we were particularly pleased with this result.’
Experiments found the virus was unable to replicate after hamsters were given two doses of the vaccine. They are the best animal model for Covid as they are prone to the same variants and symptoms as humans.
‘We witnessed strong activation of the immunological memory and the mucous membranes were very well protected by the high concentration of antibodies,’ said Dr Trimpert.
Further tests on the lab rodents found it outperformed all other currently available vaccines – probably due to immunity building up at the viral entry site.
In addition, it contains all components of the virus – not just the spike protein, as is the case with mRNA vaccines. The spike is the coronavirus’s most important weapon, but the immune system can also recognise the infection from about 20 other proteins.
Best results were provided by double nasal vaccination, followed by the combination of a muscular injection of the mRNA vaccine.
Lead author Julia Adler, a doctoral student at Freie, said: ‘This means the live vaccine could be particularly interesting as a booster.’
The researchers were also able to specifically alter the genetic code of the vaccine’s weakened virus.
Co-author Dr Dusan Kunec, from Freie, said: ‘We wanted to prevent the attenuated viruses from mutating back into a more aggressive variant.
‘This makes our live vaccine entirely safe and means it can be tailored to new virus variants.’
The study was published in the journal Nature Microbiology.
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