MONROVIA, Liberia — Liberians are overcoming their fears of Ebola to volunteer for a vaccine trial.

The gruesome toll of West Africa’s Ebola outbreak, which has killed more than 4,200 Liberians of the more than 10,000 who have succumbed to the disease, has intensified efforts to find a vaccine for a disease that previously infected relatively few people in remote areas.

One year after the World Health Organization declared the Ebola outbreak, vaccine trials are underway in Liberia and Guinea. Sierra Leone will start a trial later this month.

In Liberia, scientists have fanned out across the country to explain the studies and reduce the fear and confusion that have stymied efforts to contain Ebola.

Dr. Stephen Kennedy, the Liberian lead investigator for the study, was among the first people to volunteer for the vaccine trial, getting his injection in front of the media.

Similarly, in Guinea, authorities started the study by injecting a series of prominent officials, including the head of the country’s Ebola response.

The outreach worked in Liberia, where more than 700 people have volunteered, well beyond the 600 required, according to Kennedy.

“All of the reservations I have were explained, my doubts were cleared,” B. Emmanuel Lansana, a physician’s assistant who was the first person to participate in the study, said after he received his injection.

Enrollment will close soon for Liberia’s Phase 2 trial, which is testing two vaccine candidates for safety and for whether they produce an immune response.

“We’ve had no trouble with enrollment,” said Dr. Clifford Lane, the clinical director of the U.S. National Institute of Allergy and Infectious Diseases, which is helping to run the study. “This study has been pulled off in an extraordinarily professional, competent and efficient way.”

Liberia had not seen an Ebola case in weeks before one was confirmed Friday. The low level of the disease means that the trial’s next phase may be moved to Sierra Leone or Guinea, where the disease is more prevalent. Phase 3 will test whether the vaccines actually prevent Ebola, so it must be done in a place with active transmission.