Yellow fever virus is transmitted by Aedes aegypti – the same
mosquito that spreads the Zika virus. Symptoms include fever,
muscle pain, headache, nausea, vomiting, and fatigue. At least
half of untreated patients with severe cases of yellow fever die
within 10-14 days.
The good news is that, unlike Zika or Ebola, yellow fever can be
controlled with an effective vaccine, which confers lifelong
immunity within a month of administration. And, indeed,
vaccination forms the core of Angola’s National Response Plan,
initiated early this year with the goal of administering the yellow
fever vaccine to more than 6.4 million people in Luanda
Province. So far, nearly 90% of that target population has been
vaccinated, thanks largely to the World Health Organization, the
International Coordinating Group for Vaccine Provision, and
other countries, including South Sudan and Brazil, which
together made some 7.35 million doses of the vaccine available.
The mass vaccination effort has stemmed the spread of yellow
fever. But to end the outbreak, vaccination has to continue not
only in Luanda, where an additional 1.5 million are at risk of
infection, but also encompass other affected provinces. This will
be a major challenge.
One key problem is cost. In 2013, the yellow fever vaccine cost
$0.82 per dose in Africa – a price that most developing countries
cannot afford. A 2015 report by Médecins Sans Frontières
showed that the vaccine is now almost 70 times more expensive
than it was in 2001.
Making matters worse, even if countries have the money, there
are serious supply constraints. Senegal’s Pasteur Institute of
Dakar, one of only four facilities in the world producing yellow
fever vaccines, manufactures about ten million doses per year,
and the manufacturing process is extremely difficult to scale up.
Moreover, the Pasteur Institute is about to close down for a five-
month renovation, during which it will be unable to produce
more vaccine.
Fortunately, the situation is set to improve. The Pasteur Institute
is constructing a new facility about 30 kilometers from Dakar, in
Diamniadio, that is expected to triple production by 2019.
Another yellow fever vaccine manufacturer, Sanofi Pasteur in
France, is also expanding its manufacturing capacity. (The other
two manufacturers are based in Brazil and Russia.)
For now, however, supplies are tight. One way to stretch existing
stores could be by administering a fractional dose (one-fifth of
the usual dose), which has also been shown to protect against
yellow fever.
But even that may not be enough if the virus spreads further.
And, unfortunately, the high density of Aedes aegyptii
mosquitoes in the affected areas means that the risk of
transmission remains high.
An outbreak in a region like Asia, which lacks experience with a
yellow fever epidemic and has no capacity to manufacture the
vaccine, would be particularly difficult to control. According to
John P. Woodall, the founder of the disease-alert service
ProMED, if yellow fever spreads to parts of Asia with the right
climate and mosquito species, hundreds of thousands could be
infected (and possibly die) before vaccine stocks are delivered.
The virus also has the potential to spread to the Americas, which
are home to Aedes mosquito vectors that transmit not only
yellow fever, but also dengue, Zika, and chikungunya. Already,
the Pan American Health Organization has declared an
epidemiological alert for yellow fever in Latin America.


Source. https://www.project-syndicate.org/commentary/control-yellow-fever-threat-by-melvin-sanicas-2016-05

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