Norovirus cases are surging across the U.S. this winter, but Moderna may soon offer a solution. The biotechnology company is conducting a large Phase 3 clinical trial for a norovirus vaccine, with results expected as early as late 2024 or 2026. The study, involving 25,000 participants, is enrolling ahead of schedule, reflecting strong interest, according to Moderna’s clinical therapeutic area head for gastrointestinal and bacterial pathogens, Doran Fink.
Norovirus is a highly contagious stomach virus that causes severe vomiting and diarrhea. It spreads rapidly in nursing homes, daycare centers, and cruise ships, with infections typically peaking during winter. This season has been particularly severe, with twice as many positive tests reported in January compared to last year. The Centers for Disease Control and Prevention (CDC) also recorded a 36% increase in outbreaks as of December.
Currently, no vaccine exists for norovirus, partly due to the challenge of immunizing against its multiple strains. Moderna’s vaccine candidate targets three genotypes that are most commonly linked to infections. The shot works by training the immune system to recognize a harmless version of the virus, enabling it to respond effectively upon real exposure.
However, the vaccine does not include the genotype responsible for most infections this season. A key objective of the trial is to determine whether it offers broader protection against additional norovirus strains. Moderna notes that mRNA technology allows for quick adjustments to the vaccine if necessary.
Rather than aiming to prevent infections entirely, the vaccine’s primary goal is to reduce symptom severity and lower the risk of hospitalization. Given that norovirus symptoms appear within 12 to 24 hours of exposure, complete prevention is difficult to achieve.
Moderna sees the greatest potential in vaccinating seniors, who are at higher risk of severe complications such as dehydration. According to the CDC, people aged 65 and older account for the majority of the estimated 900 norovirus-related deaths in the U.S. annually. Healthcare workers, daycare staff, teachers, and cruise ship passengers are also identified as potential candidates for vaccination.
While investors are evaluating the commercial viability of the vaccine, analysts believe its primary use will be in high-risk environments such as nursing homes and cruise ships. Moderna has yet to test the vaccine in children, but if proven effective in adults, regulatory requirements would mandate pediatric trials in the future.
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