Corona injections protect against severe courses or even death. However, there is one thing that the current vaccines cannot do: stop the spread of the virus. New preparations from China and India for spraying and inhaling are now raising hopes.
Almost two years ago, the scientific world made a decisive breakthrough in the pandemic: the development of mRNA vaccines against the coronavirus. Since then, these and other vaccines have saved countless lives from hospitals and ventilators. So far, however, they have not been able to end the pandemic as some had hoped. They prevent people from becoming infected and passing on the virus only insufficiently and for a limited time. The reason, many experts are convinced, lies in a lack of immunity of the mucous membranes in the mouth and throat – where the virus enters the body.
However, there is now a new beacon of hope that should stop the spread of Sars-CoV-2 once and for all. At least Federal Health Minister Karl Lauterbach seems certain: “The pandemic will end when we achieve mucosal immunity, for example via nasal vaccines,” tweeted the SPD minister at the end of August. And further: “Far too little money is invested here. We could already have such vaccines.”
In fact, China and India are a step ahead of us in this respect. As the journal “Nature” reports, China’s manufacturer CanSino Biologics has modified its vaccine, which was previously administered by syringe, so that it can be converted into an aerosol for inhalation using a nebulizer. The vaccine uses an adenovirus type 5 as a means of transport for a piece of genetic information from the coronavirus. If patients inhale this vaccine, it is said to trigger an immune reaction of the mucous membranes against corona. India’s BBV154 vaccine from Bharat Biotech follows more or less the same principle. Here, a chimpanzee adenovirus is genetically modified and applied to the mucous membranes as nasal drops.
The mucous membranes have their own immune system with a special form of antibodies, explained molecular biologist Emanuel Wyler to “Zeit”. However, they would only be insufficiently stimulated by classic vaccinations. However, the upper respiratory tract is crucial in fighting off an infection, as this is where the virus attacks first. An effective immune defense there could drastically weaken the infection or prevent it entirely, is the idea behind the nasal vaccinations.
A study published in the journal “The Lancet” confirmed its effectiveness. According to this, the use of the Chinese vaccine as an inhalant was able to significantly increase the immune response of the vaccinated compared to an injection. About ten times higher titers of neutralizing antibodies were found than when the same vaccine was administered intramuscularly. However, neither the Chinese nor the Indian manufacturer have yet published the results of their phase 3 clinical trials.
“The data still look promising, you can see a good immune reaction with antibodies in the blood,” said Leif Erik Sander, vaccine researcher at the Berlin Charité, in the “Tagesspiegel”. “Unfortunately, the reaction in the oral and nasal mucosa has not been investigated.” However, it is generally assumed that an immune response in the mucous membranes provides better protection against becoming infected and passing on the virus. “We conclude this on the one hand from animal experiment data and also from observations of breakthrough infections as well as generally known facts about mucosal antibodies.”
Not all scientists agree on whether nasal vaccination could actually become the decisive factor in the pandemic. Jonas Schmidt-Chanasit, virologist at the Bernhard Nocht Institute in Hamburg, believes it is fundamentally important to also have vaccines with a different mechanism of action, for example for risk groups. “But the nasal vaccines are by no means necessary to end the pandemic,” Schmidt-Chanasit told the “Welt”. The infections that are currently occurring in the millions have already led to better mucosal immunity than the mRNA vaccines could achieve.
Epidemiologist Timo Ulrichs, however, observes a discrepancy between conventional vaccine development, which is “progressing rapidly”, and the less rapid development of other vaccines. “The technology would be there” to prevent infections, says Ulrichs. That would massively inhibit the transmission of the virus. “So, as was hoped for at the beginning of the pandemic from all anti-corona vaccines.”
However, an important question is how long the generated immunity lasts in the mucosa. Life-long protection, such as with measles, is unlikely. “Unfortunately, with Sars-CoV-2, as with other respiratory diseases, there is no sterile immunity that permanently protects against infection,” explained infectiologist Christoph D. Spinner from the Klinikum Rechts der Isar in an interview with ntv.de. Over time, the number of antibodies in the mucous membrane will also decrease – and the risk of infection will increase again.
