Vaccination against gastroenteritis coming soon?
It is feared in homes, hospitals and on cruise ships. There are no drugs against the norovirus. Researchers are now working on various approaches for a vaccine.
The norovirus is particularly feared on cruise ships, also because you can get infected again and again.
Foto: Alamy Stock Photo
We have all become acquainted with the norovirus, which causes severe gastroenteritis. In addition to the unpleasant symptoms, you often feel a certain helplessness. Because there is not much you can do about the symptoms, apart from making sure that you don’t lose too much fluid. Stomach flu is annoying for healthy people from school age to old age, but mostly harmless in countries with a functioning health system. However, they are dangerous for small children, very old people and for immunocompromised people. They are also a major problem in poor countries with poor medical care. In the case of severe dehydration, only infusions can help.
A nurse administers the rotavirus vaccine to an infant in Port au Prince, Haiti 2014. The vaccine is intended for children aged 6 weeks to 6 months.
Photo: AFP
There are no medications, so research focuses on vaccinations. There is already a vaccine for the rotavirus, which also causes gastrointestinal flu. The even more common norovirus is a difficult candidate for a potential vaccine. But now researchers are working on promising approaches.
200,000 deaths per year from norovirus
Vaccination is urgently needed. There are 700 million cases of norovirus diarrhea worldwide every year and more than 200,000 deaths, mostly among young children. The Federal Office of Public Health (BAG) estimates that there are around 400,000 norovirus infections in Switzerland every year. The disease is particularly feared in retirement and nursing homes and in hospitals. The World Health Organization (WHO) classifies the norovirus as a “major global threat to public health”.
The fact that it is difficult to develop a vaccine against the norovirus has to do with some peculiarities of the virus. What we know about the corona virus also applies to the norovirus: There are many variants that can be combined with one another again and again. That’s why you can get infected again and again.
The different noroviruses do not always use the same receptors to penetrate human cells.
In addition, the human immune response does not last very long, even against a known variant. “It is fundamentally more difficult to develop a vaccination against viruses that do not have good antibodies after they have been infected,” says Jakob Nilsson, senior physician at the Department of Immunology at the University Hospital Zurich.
Unlike the coronavirus, the norovirus is not easy to study. So far, it has hardly been possible to cultivate the norovirus in the laboratory. And there is no animal model for the scientists to work with. In addition, the different noroviruses do not always use the same receptors to enter human cells, which makes things even more difficult.
The norovirus is a survivor, it even survives temperatures of minus 18 degrees in the freezer.
Illustration: Getty Images
In one of the two new vaccinations, the molecular biologists at Washington University School of Medicine rely on the rotavirus, which is easier to research. They add an important norovirus protein to a rendered harmless rotavirus in order to trigger an immune response. Such vector-based vaccines were also used during the corona pandemic, for example in the AstraZeneca vaccine. And indeed, the experimental vaccine was successful in animal models.
“This is a promising approach,” says immunologist and infectiologist Nilsson. The immune response in the intestinal mucosa is important for a norovirus vaccine. There, antibodies must be present in sufficient concentration to prevent disease. This worked in the first tests.
The norovirus regularly causes major outbreaks in homes, hospitals, kindergartens or on cruise ships because it is so contagious and persistent. Compared to the flu virus, for example, it takes a far smaller amount of norovirus to become ill. In addition, the norovirus is a survivor. It even withstands temperatures of minus 18 degrees in the freezer, which is why you can also become infected through thawed, contaminated food that you don’t cook, such as frozen berries.
Only 20 percent of infections are due to poor hygiene
Experts have long been convinced that norovirus outbreaks can best be prevented with vaccination. It is true that hygiene also plays an important role in the preparation of food, as scientists from the American National Institutes of Health wrote in a research report. However, it is estimated that this route of infection only causes around 20 percent of norovirus infections.
Another one is still further in development Vaccine project by pharmaceutical manufacturer Takeda with virus-like particles. The developers have already successfully completed a phase II study with children between the ages of one and eight for this vaccine.
“It’s good when research pursues different approaches for a vaccine,” says Nilsson. Precisely because the norovirus is a difficult candidate. But you still have to wait a bit for both vaccines. Nevertheless, there is also good news: Around 10 to 20 percent of the population have natural protection against the norovirus and usually do not become ill during outbreaks.
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