There is currently no approved norovirus vaccine, but multiple companies are actively working towards developing one.
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Every year, between 19 and 21 million Americans experience gastroenteritis, commonly known as “stomach flu,” primarily caused by noroviruses. These infections result in numerous visits to the emergency room, hospitalizations, and approximately 900 deaths annually. The ongoing winter season in the U.S. is witnessing a significant spike in norovirus cases, with the CDC reporting the highest outbreak numbers in the past decade.
The surge in norovirus infections can be attributed to two main factors, according to Daniel Kuritzkes, chief of infectious diseases at Harvard Medical School. Firstly, the circulating virus strains evolve each year, diminishing immune protection similar to influenza and Covid. Secondly, individuals’ immunity to specific norovirus strains diminishes over time, increasing the likelihood of reinfections.
Despite the prevalence of norovirus infections, there are currently no approved treatments or vaccines available. Developing a treatment for norovirus is challenging due to the short duration of the viral infection, typically lasting one to two days, making it difficult to demonstrate efficacy to regulators. Moreover, the primary complication leading to hospitalizations is dehydration, which can be effectively managed with intravenous fluids.
Therefore, the most promising approach to combat noroviruses is through vaccination. Currently, three vaccine candidates are progressing through human trials, with Moderna leading the way by developing a norovirus vaccine using mRNA technology similar to the Covid-19 vaccine. Moderna estimates a substantial market opportunity for a norovirus vaccine, considering the significant economic impact of annual virus infections globally.
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One of the primary challenges in developing a norovirus vaccine, as noted by Doran Fink from Moderna, is the presence of multiple circulating strains that lack common immune recognition features. Immunity to one strain does not guarantee protection against others, necessitating vaccines targeting multiple strains simultaneously, similar to seasonal flu vaccines.
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