The World Health Organisation (WHO) is rerouting yellow fever vaccine supplies meant for routine immunisations in other countries to replenish Angola's emergency stockpiles that have been depleted by an outbreak of the acute viral haemorrhagic disease.
The country is facing its worst yellow fever epidemic in 30 years, according to the WHO, with nearly 200 deaths and more than 450 cases reported since January.
"The emergency stockpile [usually] has six million vaccines; the outbreak in Angola needs at least 7.5 million vaccines," WHO spokesperson Christian Lindmeier says.
"The stockpile is being replenished constantly through diverting [vaccine] shipments, which were supposed to be used for routine immunisations in other countries," Lindmeier says. "At the same time, production [of the yellow fever vaccine] is on-going. By the end of September we should be stocked up again."
There are only four yellow fever vaccine producers in the world. Lindmeier says this has resulted in a global yellow fever vaccine shortage. "The amount of vaccines they produce yearly is not enough to cover the need. All the prevention campaigns [globally] would need between 30 and 35 million vaccines. There is definitely a need for more production."
Infected mosquitoesYellow fever is transmitted by infected mosquitoes. This is the same mosquito that transmits the Zika virus and Dengue fever, according to the WHO.
Without treatment, half of the people severely infected with yellow fever will die.
The WHO estimates that up to 170 000 cases of yellow fever are recorded every year, with 60 000 people dying globally. Treatment for yellow fever is symptomatic, but it is preventable.
The yellow fever vaccine can provide 99% protection within 30 days of immunisation and a single dose of the vaccine can provide life-long immunity to the disease. In Angola, it is recommended that all babies be vaccinated by nine months. But according to government data, in 2014 only 64% of babies were vaccinated by this age.
The rapid growth of cities, such as Angola's capital, Luanda, the epicentre of the country's yellow fever epidemic, is also a major risk factor for "large and uncontrollable outbreaks", according to the WHO.
Urbanisation has resulted in huge numbers of non-immune people living in settings where "high vector and population density, the main factors contributing to increased virus transmission, are present".
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