Despite some setbacks, nasal covid-19 vaccines remain a good clue for scientists, who hope to find more effective protection with this method than with a classic injection.
This vaccine, administered by aerosol or by drops (like physiological saline solution), is of theoretical interest: by acting directly on the respiratory tract, in particular on the mucous membranes, it more effectively prevents the infection from entering the body.
Current vaccines are highly effective against severe forms of the disease, but fail to prevent simple infections.
In some countries, these nasal vaccines are becoming a reality. Two of them have just been approved, respectively in China and India.
But these authorizations were granted without public trials having demonstrated greater effectiveness of these vaccines against contagion.
Recently, in the UK, researchers from the University of Oxford who were exploring the possibility of administering the AstraZeneca vaccine nasally announced the failure of a first clinical trial in early October.
The results, published in the journal eBioMedicine, showed that the thirty people who received the nasal vaccine developed a lower immune response than those who used a classic, injection vaccine.
Scientists, however, insist that the trail is worth exploring.
– Live attenuated vaccines –
“You shouldn’t be discouraged” by these findings, says virologist Connor Bamford, of Queen’s University in Belfast.
Although initial results are poor, this expert points out, they represent the basis from which progress can be made, once you have verified what went wrong.
Nasal vaccines that are already in circulation – against the flu or polio – are “alive”, recalls this expert, that is, they use an attenuated version of the virus to stimulate the immune system.
Instead, AstraZeneca’s vaccine – developed with the University of Oxford – works through a “viral vector”, which is a harmless virus other than the coronavirus that carries some of its RNA.
– Lack of funds –
The Oxford researchers conjure up another hypothesis of their drug’s failure: their spray does not penetrate the body sufficiently and its effectiveness would greatly improve if it reached the lungs.
“It is possible that this nasal vaccine would simply be ingested and destroyed in the stomach, which could be avoided if it reached the lungs directly,” said researcher Sandy Douglas, who led the studies, in a statement.
There is an auspicious sign: no serious secondary symptoms were detected, either during that trial or after tests with the Chinese and Indian nasal vaccines.
The promoters of these nasal vaccines aren’t just facing scientific challenges. In many highly developed countries, unused batches of vaccines are piling up.
That is why the project by the French biotechnology company TheraVectys, in alliance with the Pasteur Institute, launched in 2020, did not go beyond an animal test.
“We are not in the interest of public bodies, nor of large pharmaceutical companies, in starting the phase of clinical trials on humans,” Pierre Charneau, scientific director, explained to AFP.
Rather, the interest of nasal vaccines is to stop massive infections, explains Martin Moore, scientific director of the American biotechnology company Meissa.
“The only way to control this virus is to break its chain of transmission (…). With a nasal vaccine we can get it,” he told AFP.
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