If you’ve ever suffered through food poisoning, odds are that the bug you caught was norovirus, the most common foodborne illness in the world. Just in the United States, norovirus causes an annual estimated 19 to 21 million illnesses and contributes to 56,000 to 71,000 hospitalizations and 570 to 800 deaths, according to the U.S. Centers for Disease Control and Prevention (CDC). Worldwide, norovirus causes 20 percent of diarrheal illness and as many as 100,000 child deaths each year. Looking at the numbers, it’s easy to see why health professionals are becoming increasingly interested in developing a norovirus vaccine, and one or more may be on the way. In February 2015, CDC worked with the Bill & Melinda Gates Foundation to organize a meeting between experts from 17 countries to discuss the current state of research into a norovirus vaccine. Experts at the meeting included medical professionals and representatives from government, academia, and major charitable organizations. At least four different teams around the world are currently developing vaccines, according to Benjamin Lopman, Ph.D., epidemiologist with the CDC’s Division of Viral Diseases. However, he cautioned that the first vaccines are still likely five or more years from reaching the market. The norovirus vaccine furthest along in development is being made by Japanese pharmaceutical company Takeda Pharmaceuticals, Lopman said. Another is under development by a team in Finland, and two others are in the works in the U.S. Before reaching marketplaces in the U.S. and elsewhere, each of the vaccines needs to go through several more phases of clinical trials and approvals by various committees, such as the Advisory Committee for Immunization Practices in the U.S. Vaccine makers still have a number of questions to answer as well. For one, no one really understand how humans develop immunity to norovirus in the first place. And when they do develop immunity, it’s difficult to know how long it will last or how well that immunity protects against other strains of the virus. Children younger than five years old and the elderly would have the most to gain from a norovirus vaccine, Lopman said, though the virus also causes enormous economic damage by infecting healthy adults who must often miss work in order to care for themselves or family members. Takeda Pharmaceuticals will likely be the first company to conduct large-scale efficacy trials on a norovirus vaccine in the coming years. It’s difficult to predict when the vaccines will reach end-users, but they’re likely to hit the U.S. and other developed nations before the rest of the world, though vaccines are reaching developing nations more quickly today than they have previously, Lopman said. “There used to be a big time gap for when vaccines reached low-income countries, though that’s shortening,” he told Food Safety News. “But there’s still obviously an economic component — you have to find funding to introduce the vaccine to low-income countries.” Until a vaccine is ready, Lopman recommended common measures for preventing norovirus infection: Washing hands, disinfecting surfaces, not preparing meals while ill, and cooking food thoroughly. “From the CDC’s perspective, we can just keep a close eye on these vaccines as they develop,” Lopman said.