Published On: Wed, Dec 7th, 2016

Winning the war against yellow fever

© WHO/D. Lourenco

Four months have passed without a single case of yellow fever related to the outbreak in Angola and the Democratic Republic of the Congo, thanks to the joint response activities of national health authorities, local health workers, WHO and partners.

“It is incredible that such a large and diverse group of partners have come together to protect people against yellow fever,” said Dr Matshidiso Moeti, WHO Regional Director for Africa. “I’m also proud of the Organization-wide support. Staff from across all three levels of WHO – country offices, the Regional Office for Africa and headquarters – have come together under one integrated incident management system. Each level has played an important role: starting from the country level where the outbreak is occurring, to the Regional Office for oversight, command and control and the global level coordination support.”

The outbreak, which was first detected in Angola in December 2015, had caused 962 confirmed cases of yellow fever across the two countries (884 in Angola 78 in DRC) by 16 November 2016, with more than 7300 suspected cases. The last confirmed case reported in Angola was on 23 June and DRC’s last case was on 12 July.

More than 41 000 volunteers and 8000 vaccination teams were involved in the mass immunization campaigns. The vaccines used came from a global stockpile co-managed by Médecins Sans Frontières (MSF), International Federation of the Red Cross and Red Crescent Societies (IFRC), UNICEF and WHO. In the first 6 months of 2016 alone, the partners delivered more than 19 million doses of the vaccine – three times the 6 million doses usually put aside for a possible outbreak. Gavi, the Vaccine Alliance financed a significant proportion of the vaccines.

“This is the result of a gargantuan effort,” said Dr Margaret Lamunu, Yellow Fever Incident Manager at WHO HQ. “30 million people have been vaccinated across the 2 countries – can you imagine the sheer logistics of getting vaccines out to that many people? Many of these people live in dense urban areas or remote rural settings. But we worked tirelessly with the respective governments and our partners – notably Gavi, UNICEF, CDC and all the GOARN partners – and together, we pulled it off.”

A new approach to vaccination for yellow fever outbreaks

When, given the unprecedented nature of the outbreak, more vaccine was needed, WHO consulted global experts on the introduction of an innovative new strategy: an emergency fractional dose of the yellow fever vaccine.

“We had seen studies showing that one fifth of the usual dose of the yellow fever vaccine would provide immunity for at least a year and probably longer,” explained Sergio Yactayo, WHO expert on yellow fever.

“In an urban emergency situation like this one and to ensure greater coverage with the limited available global vaccine stocks, we knew that a fractional dose strategy should provide more people with the protection required to stop the outbreak. And fortunately the people of the Democratic Republic of the Congo were willing to take advantage of this new approach to interrupt transmission in the sprawling capital city of Kinshasa where more than 10 million people were at risk ahead of the rainy season. Their support is one of the key reasons why the country has not seen an outbreak-related case since July.”

Broad support for the yellow fever response

In addition to supporting mass vaccination campaigns, WHO has worked with the governments of Angola and the Democratic Republic of the Congo and 56 global partners to strengthen laboratory capacity and disease surveillance, control the spread of mosquitoes and engage communities on how to protect themselves.

The Organization’s response to the outbreak has been possible thanks to financial support from Angola, Gavi, the Vaccine Alliance, BioManguinhos, CERF, Germany, the ICG Revolving Fund, Japan, USAID, and the newly created WHO Contingency Fund for Emergencies.

“We’re thankful to the governments of both Angola and the Democratic Republic of the Congo for their leadership of the response to date. We’re not finished yet, however,” Dr Moeti continued. “We need to keep a close eye on the situation in both countries, particularly with the coming rainy season – this is a peak time for yellow fever-carrying mosquitoes. We need to continue working together to ensure this outbreak is truly over, and to prevent future outbreaks.”

Preventing future yellow fever epidemics

Outbreaks like the one in Angola and the Democratic Republic of the Congo could become more frequent in many parts of the world unless coordinated measures are taken to protect people most at risk. Climate change, the mobility of people within and across borders, and the resurgence of the Aedes aegypti mosquito, have combined to increase the likelihood of yellow fever epidemics.

Awareness of this increased global risk brought together a broad coalition of partners in Geneva, Switzerland, recently to develop a new global strategy for the “Elimination of Yellow fever Epidemics” (EYE). Key components of the strategy include preventive vaccination (both in routine immunization schedules and mass campaigns), an expanded global vaccine stockpile for outbreak response and support for greater preparedness in the most at-risk countries.

“The current battle against yellow fever in Angola and the Democratic Republic of the Congo is coming to a close,” Dr Moeti explained. “But the broader war against the disease is just getting started.”

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