Researchers have said an experimental Ebola vaccine shows promise in an early clinical trial, but requires much more testing, New York Times News Service reports.

The trial included 120 healthy adults in China who received either a low or high dose of the vaccine, or a placebo. 28 days later, 38 of 40 people in the low-dose group and all 40 of those in the high-dose group showed an immune response to the vaccine.

No serious side effects occurred among the participants who received the vaccine.

While the results suggest the vaccine is effective and safe, more long-term testing is needed to determine whether it can actually protect people against Ebola, according to the authors of the study published March 25 in The Lancet.

The vaccine is based on the strain of Ebola that has been circulating in the West African outbreak. The researchers note that, until now, all tested Ebola vaccines have been based on the Ebola strain from the 1976 outbreak in Zaire.

The vaccine was developed by the Beijing Institute of Biotechnology and Tianjin CanSino Biotechnology in China. Both helped fund the study, along with China National Science and Technology.