The misery of the common stomach flu may be coming to an end. Pharmaceutical company Moderna has launched a large-scale Phase III trial that will test out a vaccine against norovirus, a frequent and sometimes dangerous source of food poisoning.
Moderna’s Nova 301 trial is set to kick into full gear this year, following the first dose given to a volunteer last September. Around 25,000 volunteers over the age of 18 are expected to enroll in the randomized, double-blinded, and placebo-controlled trial, which will ultimately take two years to complete. People across the world will be able to participate in the research, including throughout much of the U.S.
Norovirus is the leading cause of foodborne illness in America, accounting for around 20 million cases every year. Most cases of norovirus are short-lived—if plenty uncomfortable—with symptoms like diarrhea, vomiting, and flu-like illness lasting up to three days. For many, it’s a miserable but manageable ordeal. However, a significant number of people seek medical care, leading to over two million doctor visits and nearly half a million emergency room trips each year. In rare cases, the infection can become severe enough to result in hospitalization or even death. About 100,000 Americans are hospitalized by norovirus, while 900 die from it every year. It’s an even bigger issue in parts of the world with weaker sanitation and health programs.
“Norovirus is a significant public health concern that affects millions of people worldwide each year, leading to severe symptoms and, in some cases, hospitalization,” said Stéphane Bancel, CEO of Moderna, in a statement last fall. “By advancing our investigational norovirus vaccine into a pivotal Phase 3 trial, we are one step closer to potentially providing a new tool to prevent infection from this highly contagious virus, which places a significant burden on health systems globally.”
Though norovirus has long been a thorn in humanity’s side, the urgency for a vaccine is now certainly high. Following a short lull throughout the early pandemic era, norovirus has surged back as of late in the U.S. During the latter half of 2024, around 500 outbreaks of norovirus were reported, a substantial increase compared to the previous year. And this winter’s norovirus season is on track to be the worst experienced in over a decade.
Scientists have struggled to develop a successful norovirus vaccine. Historically, we haven’t been able to grow the virus in the lab or in small animals, hampering our study of it. The virus is also naturally hardy to our defences. There are several types of disease-causing norovirus circulating at any one time, and being recently infected by one strain doesn’t necessarily protect you from others. Our natural immunity to a specific strain also tends to wane over time as well, perhaps lasting as little as a few months for some.
But more recently, scientists have been able to create effective lab models for studying norovirus, and they’ve developed some promising strategies for vaccination. Moderna’s vaccine candidate, for instance, tries to create immunity by training the body to target virus-like particles (VLPs) that closely resemble norovirus but which contain no actual virus. The candidate uses the same basic mRNA technology implemented in Moderna’s covid-19 vaccines to accomplish this. mRNA vaccines prompt the body’s cells to produce a target protein that’s then recognized by the immune system as a possible threat (in this case, the norovirus VLPs).
The company’s candidate is code-named mRNA-1403, and it’s designed to induce immunity to at least three common types of norovirus, which will hopefully ensure widespread protection. While norovirus is an awful experience for everyone, it’s most likely to cause serious illness in vulnerable populations such as people with weakened immune systems and the elderly. So the majority of trial volunteers (20,000) will be over the age of 60. Other companies are trialing their own norovirus vaccines for children as well, however.
There are more than 250 study sites for the Nova 301 trial across the world, with more than 100 located in the U.S. alone. Participants are required to be in generally good health (this can include having well-controlled chronic health conditions), and to have had no recent history of gastrointestinal illness, among other criteria. The main part of the trial is planned to run for two years, with the completed results expected by May 2027. Those interested in potentially participating can take a survey created by Moderna here.
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