Democratic Republic of Congo and Angola began one of the biggest ever emergency vaccination campaigns in Africa this week, working with the World Health Organization (WHO) to curb a yellow fever epidemic that has killed hundreds this year.

Health officials expect to vaccinate 14 million people over the next 10 days including some 8.5 million in the densely populated Congolese capital, Kinshasa, where the disease's presence has sparked fears of a far wider spread.

Vaccinations started in Angola on Monday and about 41,000 health workers have been deployed across more than 8,000 sites with 17.3 million syringes available regionally, WHO said on Tuesday. There are about 6,000 suspected cases in the region.

A small but significant fraction of cases die from jaundice, bleeding and multiple organ failure. More than 400 people have died of the virus since December.

The campaign is being accelerated to try to stop it spreading before the rainy season starts in September and makes more remote parts of the region inaccessible. Other challenges include a lack of reliable power to keep vaccines cold.

"By the end of this vaccination campaign ... we are going to put an end to the progression of yellow fever," Congo's Minister of Health, Felix Kabange Numbi Kabange, told reporters on Tuesday at a ceremony to mark the start of the campaign.

China and Japan, the World Bank, WHO and the U.N. Children's Fund as well as the Global Alliance for Vaccines and Immunization are financing the campaign, WHO spokesman in Congo, Eugene Kabambi, said.

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About 2 million people were vaccinated in Kinshasa during campaigns in May and July. Overall, some 13 million people in Angola and 3 million in Congo have been vaccinated this year.

The outbreak has spread as far as China, carried by workers returning from Angola, but WHO spokesman Tarik Jasarevic said on Tuesday he was optimistic it could be contained.

"The WHO Emergency Committee will reconvene in coming weeks (and) will re-evaluate the situation but we think that the outbreak is manageable if we can protect enough people with the vaccine," he told reporters in Geneva.

The campaign also marks the first time that fractional doses of the vaccine will be given in order to stretch limited supplies amid a global shortage.

The one-fifth dose, which will be used in Kinshasa, protects for at least 12 months but does not give lifelong immunity.