AstraZeneca’s adenovirus-based vaccine does not produce adequate immunity as a nasal spray. The company will therefore no longer develop it in this form. This is the result of a first clinical study on 130 people in Wuhan, carried out by a team led by Alexander D. Douglas from the University of Oxford.
As the working group writes in the journal “eBioMedicine”, they were able to detect practically no antibodies in the nasal mucosa after one dose of nasal spray, and after the second dose only in some of the test subjects.
Overall, such a type of vaccination produces only weak and inconsistent immune reactions, which are not sufficient to continue pursuing the approach in this form, according to the publication.
Experts hope that nasal spray vaccinations will provide better protection against infection with Sars-CoV-2 than previous vaccines offer. These produce only a few antibodies in the mucous membranes, so that the virus has a clear path at the site of the first infection.
The hope is that an aerosol from the adenoviruses used for vaccination will produce effective protection right there. However, it is much more difficult to produce such a vaccine.
The mucous membranes are a very effective barrier against pathogens and also keep vaccines out. That’s why it’s difficult, for example, to dose so that enough of the virus enters cells to generate a robust immune response.
Experts therefore suspect that vaccines based on the non-replicating adenoviruses are generally only suitable for nasal vaccinations to a limited extent.
There is a FluMist nasal spray vaccination against influenza; however, it is based on a weakened influenza virus that multiplies in the mucous membrane. So far there is no such live vaccine for Covid-19.
There may also be differences between the adenovirus lines used. The nasal spray vaccine from the Chinese manufacturer Cansino, which was approved in September, produces a better immune reaction in the blood than the preparation from AstraZeneca that has now been tested – however, there is no data on the immunity in the mucous membranes of this vaccine.
The dosage form may also play a role. For example, Cansino uses a nebulizer to create an aerosol. The nasal vaccine BBV154 from the Indian manufacturer Bharat Biotech, which was also approved in September 2022, is administered as nasal drops.
Both generated a better immune response than AstraZeneca’s nasal spray in clinical studies. This is now being redesigned after the failure of the study; in addition to a changed dosage form, the experts will possibly also adjust the dose and any active enhancers.
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The original to this article “Nasal spray vaccine from AstraZeneca failed” comes from Spektrum.de.