(Photo: AP)

Drugmaker Merck says it will ship another approximately 120,000 doses of an experimental Ebola vaccine to Congo by the end of next month amid the second deadliest outbreak in history.

Associate Vice President Lydia Ogden told the World Economic Forum that the company is committed to having a ready stockpile of 300,000 doses and already has shipped 100,000 to the World Health Organization.

Health officials have called the experimental vaccine highly effective against the virus.

Congo’s health ministry says more than 63,000 people have received the vaccine in the outbreak that was declared on Aug. 1 in the country’s densely populated northeast near Uganda and Rwanda.

Carrying out vaccinations is complicated by rebel attacks, poor infrastructure and in some cases hostility from communities that have never faced an Ebola outbreak before.