German scientists are currently researching the possibility of administering coronavirus vaccinations via a nasal spray. The idea is to provide better protection against coronavirus and its variants, and also slow down the rate at which the virus mutates.

Nasal spray being developed to replace injections

Despite ongoing efforts to vaccinate people all over the world, the number of coronavirus infections continues to rise, spurred on by the Delta mutation. The problem is that current coronavirus vaccines do not guarantee “sterile immunity”, as the virus can still infect and be spread amongst vaccinated people. Thus, there is still a real risk of future outbreaks.

Researchers have begun looking into other, more effective ways of vaccination and one such method is via a nasal spray. Reinhold Förster, an immunologist from Hannover Medical School, and Gerd Sutter, a virologist from the Ludwig Maximillian University in Munich, have been researching a nasal spray vaccine, which uses the cowpox virus as a vector to deliver the coronavirus spike protein into the body, in much the same way the traditional coronavirus vaccines by AstraZeneca and Johnson & Johnson work. The two scientists have already been able to immunise animals with the spray

The idea for a nasal spray vaccine is also being researched by AstraZeneca. Their nasal spray vaccine has already moved into phase one clinical trials. Following successful trials on animals, the international company is planning on enrolling around 30 adults for the next stage of the trials.

Do nasal spray vaccines actually work?

It is hoped that nasal spray vaccinations will provide better protection against the coronavirus than traditional vaccines, since they have the potential to stop vaccinated people from being infected, as well as limiting the spread of the virus. "That is the great hope with the nasal spray vaccines that they generate real sterile immunity," Förster said.

Inhaling the vaccine causes antibodies to be formed in the places that are most susceptible to coronavirus; that is the airways and lungs. "The coronavirus penetrates the body via the respiratory tract and causes the greatest damage in the case of an illness in the lungs," Förster explained. Researchers believe that the B and T immune cells, which are found largely in the lungs and help the body’s immune system to remember previous threats and muster its defences, will complement a nasal spray vaccine and prevent the virus from moving to the rest of the body.

In this way, the spray vaccines help slow down the rate of mutation, as the virus is unable to test how to bypass the body’s defences. This helps prevent so-called “escape mutations”.

Further research needed

It is still unclear whether spray vaccines will actually be approved since none of the spray vaccines have advanced far enough in clinical trials to be considered for approval by authorities.

Nasal vaccines are currently a relatively limited practice, with only one nasal spray vaccine being approved against influenza. It is a live vaccine that uses weakened influenza viruses and is mainly used for vaccinating children. Currently, no approved coronavirus vaccines are live vaccines.