Angola: Yellow fever outbreak exposes vaccine supply dilemma


23 Apr 2016 | by
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Angola: Yellow fever outbreak exposes vaccine supply dilemma

The worst yellow fever outbreak in decades has killed 250 people in Angola and is straining global vaccine supplies, posing a dilemma for health officials who fear it could spread further in Africa and possibly into Asia.

The disease already caused the death of one Kenya in March this year

Between 15 and 18 March 2016, the National IHR Focal Point of Kenya notified WHO of 2 imported cases of yellow fever. Both cases were male Kenyan nationals, in their early 30s, working in Luanda, Angola. Both travelled while symptomatic and none were vaccinated against yellow fever prior to traveling to Angola.

 

The first case developed symptoms on 8 March in Luanda and travelled to Kenya on 12 March. At his arrival, he was hospitalized in a private clinic in Nairobi and was later referred to another health care facility. The patient died after experiencing multi-organ failure.

 

The second case presented symptoms on 1 March in Luanda, and flew back to Kenya on 7 March. He went to his home town (Namanga) on the Kenyan-Tanzanian Border. He returned to Nairobi to seek treatment on 11 March where he was hospitalised. The patient was treated and has since recovered and been discharged.

 

After the two cases, the Kenyan government has since urged all county health departments to enhance disease surveillance, in particular  yellow fever, at points of entry within the country.

 

Some experts have called for a radical switch in strategy to use just one-tenth of the usual vaccine dose to conserve scarce stocks but the World Health Organization (WHO) says it can't be sure this would work.

Yellow fever is transmitted by the same mosquitoes that spread the Zika and dengue viruses, although it is a much more serious disease with death rates as high as 75 percent in severe cases requiring admission to hospital.

The condition, which takes its name from the jaundiced color of some patients, has spread to the Democratic Republic of Congo and there is concern it could gain a foothold for the first time in Asia.

The WHO says cases of yellow fever imported into China, which has close commercial ties with oil-rich Angola, show that "this outbreak constitutes a potential threat for the entire world".

And it is warning that further spread elsewhere in Africa and Asia would increase the squeeze on vaccine supplies and could interrupt routine immunization.

Adding to the problem is the complicated process of making yellow fever vaccine, which means there is no quick way to boost supplies. Manufacturers, including the Institut Pasteur, government factories in Brazil and Russia, and French drugmaker Sanofi, use a time-consuming method involving sterile chicken eggs.

A short-term solution could be to slash the dose, since research suggests just one-tenth can produce the same immune response as a full dose, according to Jack Woodall, a retired virologist who formerly worked for the WHO and the U.S. Centers of Disease Control and Prevention.

"We need to get a low-dose vaccine authorized as soon as possible because if we keep using full doses we will never catch up," he said.

Woodall and colleagues laid out the case for the emergency use of a one-tenth dose in an article in The Lancet medical journal on April 16.

The WHO, however, is not convinced. A spokesman said more research was needed to measure immune response in children and duration of protection. The availability of suitable syringes for delivering a smaller dose was also a limiting factor, he said.

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