Angola's yellow fever outbreak exposes vaccine supply dilemma
Death rates as high as 75% in severe cases requiring admission to hospital
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.
Most patients improve and their symptoms disappear after 3 to 4 days, according to the World Health Organization.
But death rates from yellow fever as high as 75 per cent in severe cases requiring admission to hospital.
The condition, which takes its name from the jaundiced colour 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."
Low-dose vaccine proposed
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.
"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.
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.
With files from CBC News