Congo will not permit the use of further experimental vaccines as it combats an Ebola outbreak because doing so risked “confusing the population,” the government said on Friday.

“Due to a lack of sufficient scientific evidence on the efficacy and safety of other vaccines, and the risk of confusing the population, it was decided that no clinical trial of vaccines will be authorized during the current Ebola outbreak,” the health ministry said in a daily bulletin.

But the government did not rule out using other vaccines in the future.

Health workers have vaccinated more than 130,000 people during the nearly year-long epidemic in eastern Democratic Republic of Congo with an experimental vaccine manufactured by Merck that has proven highly effective.

But the outbreak, which is the second worst in history, continues to spread, due largely to mistrust by people in eastern Congo of the response and armed attacks against health workers that have limited access to patients.

Misinformation propagated by some community leaders in eastern Congo has led people to refuse vaccinations or treatment, and the government fears using a second vaccine would stoke further conspiracy theories.