PARIS, Oct 18, 2022 (BSS/AFP) - Nasal vaccines could still be a powerful
future weapon in the fight against Covid-19 despite "disappointing" recent
trial results for an AstraZeneca spray, experts say.

By entering the body the same way as the virus, nasal vaccines aim to build
immunity in the mucous membrane that lines the nose and mouth.

This could block people from getting infected in the first place -- and also
potentially hamper those who have Covid from spreading it further.

That would represent a huge boost compared to traditional shots in the arm,
which have proved very effective at preventing severe Covid but perform far
less well when it comes to stopping transmission.

Last month China became the first country to approve a needle-free Covid
vaccine, an aerosolised mist inhaled through the nose and mouth using a
nebuliser device, while India greenlit a homegrown nasal drop vaccine days
later.

With some wondering when Western nations would catch up, last week Oxford
researchers revealed the results of a phase 1 trial for a simple nasal spray
using the AstraZeneca vaccine.
 
However, the vaccine promoted mucosal antibodies only in a minority of the
participants, and the immune responses were weaker compared to those from
traditional vaccines, according to a study published in the journal
eBioMedicine.

- Don't be 'too downhearted' -

"The nasal spray did not perform as well in this study as we had hoped," said
the trial's chief investigator, Sandy Douglas of Oxford University.

"This was quite different from recent data from China, which has suggested
good results can be achieved by delivery of a similar vaccine deep into the
lungs with a more complex nebuliser device," Douglas said in a statement.

"One possibility is simply that the majority of the nasal spray vaccine ends
up being swallowed and destroyed in the stomach -- delivery to the lungs
could avoid that."

Connor Bamford, a virologist at Queen's University Belfast, told AFP that it
was important to "not be too downhearted" about the AstraZeneca results.

He said that working out exactly why the nasal spray fell short could help
researchers discover how to make a future version more effective.

Unlike AstraZeneca, successful nasal vaccines used for other diseases such as
polio, rotavirus and influenza are all live vaccines, which means they
replicate inside the nose, Bamford said, potentially pointing a way forwards
for researchers.

Eric Tartour, an immunologist at the European Hospital Georges Pompidou in
Paris, said that while the AstraZeneca results "are indeed disappointing", he
did not think the news "dampens hope for nasal vaccines".

It was "reassuring" that the AstraZeneca, Chinese and Indian nasal vaccines
have not shown any serious side effects, he added.

Around 100 different intranasal Covid vaccines are under development
worldwide, according to analysis by health data firm Airfinity and Nature
last month, with some 20 being tested on humans.

Russia and Iran have also approved nasal vaccines. However, like China and
India, they have not published trial data showing that their vaccines stop
transmission in a peer-reviewed journal.

And with falling inoculation rates worldwide leading some countries to
destroy millions of expired doses, the demand for a new Covid vaccine remains
unclear.

- 'Wake up and lead' -

For example, in 2020 France's Pasteur Institute and biotech firm TheraVectys
developed a nasal vaccine candidate that was found to block transmission and
produce antibodies for different variants in tests on animals, according to
chief scientific officer Pierre Charneau.

However, the vaccine has not "aroused enough interest from funding agencies
or 'Big Pharma' to hold trials on humans," so the firm has turned its focus
back towards cancer vaccines, Charneau said.

US biotech firm Meissa Vaccines has developed a nasal vaccine shown to
produce an immune response in phase 1 trials on humans, said its chief
scientific officer Martin Moore.

So how long could it take for such a nasal vaccine to be made available to
the public? It depends, Moore said.

He called for the world to put similar resources into creating a nasal
vaccine as it did into the first round of Covid jabs, which were developed
and deployed en masse in less than a year -- the fastest rate in history.

"If there was a Warp Speed 2.0, and there should be, our vaccine could be
available to the public with a similar timeline," Moore said.

"Reducing transmission is the best way to gain control over the virus," Moore
said. "The challenge is proving that a nasal vaccine can actually do this,"
he added.

"The upside to our health and economies is enormous. Western countries need
to wake up and lead."