Norovirus cases are surging across the U.S., exceeding numbers from the past decade, according to the CDC. Moderna is in Phase 3 trials with an mRNA vaccine, potentially the first of its kind, to combat this highly contagious virus. The trial's progress coincides with the emergence of a new norovirus strain, adding complexity to the vaccine's development.
Understanding the Norovirus Threat
Norovirus, commonly known as the "stomach flu," is a leading cause of gastroenteritis, characterized by vomiting and diarrhea. Dr. Edmund Milder, a pediatric infectious disease specialist at Rady Children’s Hospital and UC San Diego Health, notes that there are nearly 50 different norovirus genotypes, each requiring a specific immune response for protection. While symptoms typically last a few days, severe cases can lead to hospitalization and even death, especially among older adults and infants. The CDC reports approximately 100,000 hospitalizations and nearly 1,000 deaths annually in the U.S. due to norovirus infections.
Challenges in Norovirus Prevention
Unlike many viruses, norovirus requires very few particles to cause infection. It also possesses a hardy outer layer, enabling it to persist on surfaces for extended periods and resist common disinfectants like hand sanitizer. Effective prevention relies on frequent handwashing with soap and water for at least 20 seconds and using diluted bleach solutions to disinfect surfaces.
Moderna's mRNA Vaccine Approach
Moderna's vaccine candidate includes three different norovirus types to broaden protection against circulating strains. Dr. Doran Fink, therapeutic head of gastrointestinal pathogens and bacterial vaccines at Moderna, explains that the multivalent approach aims to provide robust protection against severe disease. The mRNA platform allows for rapid adaptation to new viral strains, similar to the strategy used for annual flu vaccines. Initial studies have shown that the mRNA shot generates antibodies that effectively block the norovirus protein in human gut cells.
Clinical Trial Details and Future Prospects
Currently, Moderna is enrolling 25,000 participants worldwide in its Phase 3 trial. Volunteers will be monitored for at least six months to assess the vaccine's effectiveness. However, the emergence of a new norovirus strain that is causing soaring numbers of cases in parts of the world, including England, may complicate the trial. According to Patrick Moore at the UK’s National Institute for Health and Care Research, one of the most prevalent strains isn’t in that jab. The vaccine is not designed to prevent infection entirely but to reduce the severity of illness and the risk of hospitalization, particularly for vulnerable populations. Moderna expects to complete enrollment in the spring and will continue to gather data on the vaccine's real-world effectiveness.
