SAN FRANCISCO — A vaccine in early testing partially protects against a common diarrhea-causing virus, a small trial finds. The culprit, norovirus, is a group of viral strains that includes the infamous Norwalk virus, which plagues some cruise ships. Norovirus causes up to 21 million infections each year in the United States, the Centers for Disease Control and Prevention estimates.
Most people have experienced a norovirus infection, said study coauthor David Bernstein, an infectious disease physician at the University of Cincinnati. He presented the study’s findings October 4 at ID Week, a meeting of infectious disease specialists. Symptom severity varies widely, but the infections can be lethal in elderly and immune-compromised people, he said. Norovirus kills up to 800 Americans every year, according to the CDC.
Bernstein and his colleagues enrolled 98 healthy adults in the trial, with 50 receiving two shots of the vaccine and 48 getting placebo shots. A month later, all drank water contaminated with norovirus.
Slightly more than half of each group became infected, but the vaccinated people were less likely to feel sick. Among them, only one-fifth had vomiting or diarrhea or both, and no case was severe. Of the unvaccinated people, two-fifths had such illness and four cases were severe.
The vaccine, made by Takeda Pharmaceuticals of Osaka, Japan, contains viral particles of the classic Norwalk strain and particles of another common norovirus strain. Combined, these strains cause up to 80 percent of norovirus infections, Bernstein estimated. The particles elicit immunity but cannot cause infection.
“The short-term benefits [of this vaccine] are very, very attractive,” said Andrew Pavia, a pediatric infectious disease physician at the University of Utah in Salt Lake City. That’s true even if it doesn’t end up offering long-term protection or lead to the extinction of norovirus strains, he added. Bernstein agreed, noting that the norovirus vaccine — if further testing results in approval — might prove useful to the military, healthcare workers and food handlers. “You could make a case for giving it to children,” he said, and of course, to people going on cruises.