Chinese researchers have shown that a new vaccine against the hepatitis E virus (HEV) can provide protection for at least four and a half years, HealthDay reports.

The new findings, published in the New England Journal of Medicine, show that hep E is now a vaccine-preventable disease. That’s good news, considering that there is currently no treatment available for an HEV infection.

Hep E is relatively uncommon in the United States, but is a leading cause of liver disease and failure in the developing world, especially in regions where sanitation is poor. The virus is spread through contaminated water and person-to-person contact.

The HEV vaccine was originally licensed in China in 2011, but until now researchers say they have not known how long the shot could actually provide protection.

According to the World Health Organization, about 20 million people get hep E every year. Of those, about 3 million people will develop acute liver disease and nearly 57,000 will die. HEV is most life-threatening among pregnant women.