"Vaccination through the nose - do new hopefuls bring sterile immunity?" Jeanne Turczynski, science editor, discussed vaccination with nasal vaccines with high-level experts from science, healthcare and industry. The consensus was that there is still a long way to go before so-called mucosal vaccines can be used routinely and, if so, only as a supplement to current vaccines.
Coronaviruses spread primarily through the air and generally reach the nose, throat and lungs first. Therefore, the obvious approach is to fight the pathogen in the mucous membranes and, optimally, to prevent infection entirely. Numerous research groups have been working on nasal vaccines since the beginning of the pandemic.
The current state of research was discussed by Prof. Clemens Wendtner, Chief Physician of Infectiology and Tropical Medicine at the München Klinik Schwabing, Dr. Thomas Frischmuth, CEO and CSO of baseclick and baseclick vaccine, Prof. Reinhold Förster, Head of the Institute of Immunology at the Medizinische Hochschule Hannover, and Prof. Christian Bogdan, Director of the Institute of Microbiology at the Universitätsklinikum Erlangen/FAU Erlangen - Nuremberg and member of the STIKO.
In principle, the approach of nasal vaccines, which prevent transmission of the infection at the point of entry, is highly interesting and needs to be addressed scientifically. Key advantages would be: They are easy to apply and can therefore be used by laypersons. However, the common tenor of the experts is that there is still a long way to go before a product can be created that has the necessary efficiency and induces an appropriate immune response, not to mention sterile immunity.
In the future, however, the use of nasal vaccines as boosters is conceivable, especially in combination with the current vaccines applied intramuscularly. At the instant, however, a nasal corona vaccine for "sterile immunity is an illusion," Prof. Wendtner said.
More potential, especially for other respiratory diseases, was attributed to inhaled vaccines, which should act specifically in the lungs. It would be important to develop vaccines against influenza or RSV, for example, that enable a highly efficient response against different viral variants and an immune memory.
Potential side effects due to proximity of the olfactory organ to the brain are seen as a major medical challenge in the development of nasal vaccines. In 2001, a nasal influenza vaccine from a Swiss pharmaceutical company was already withdrawn from the market after cases of facial paralysis occurred in vaccinated individuals. Overreactive immune responses would also have to be taken into account. These could occur in the lungs because of the large amount of immune cells involved, the experts said.
The use of nasal or inhaled mRNA vaccines in oncology - both preventive and therapeutic - is also of interest. Dr. Frischmuth sees great potential here, because "mRNA is very specific and can be produced very quickly. This would allow to stimulate immune responses in cancer patients in an individualized way and to elicit a necessary T-cell immune response." This would allow cancer cells to be kept at bay.
And another aspect was brought into the picture: the general acceptance of vaccines. Here, a lot of educational work still needs to be done in society, and it needs to be explained, how a vaccine works exactly. "The form of application is not the decisive point here," says Prof. Bogdan.
Conclusion of the experts: It is still a long way until so-called mucosal vaccines can be used routinely for the necessary immunity. Moreover, the vision would be: vaccines that are broader and more specific, trigger an appropriate immune response, and are also durable. "We will have a mix that is broad but also specific," predicts Prof. Förster. Ultimately, there will likely be a mix of intramuscular vaccines, nasal sprays and inhalations.