FIRST
INFECTION
FIRST
INFECTION
SECOND
INFECTION
ADDITIONAL
INFECTIONS
RISK OF
ILLNESS,
TYPICALLY
MILD
RISK OF
ILLNESS,
TYPICALLY
MILD
RISK OF
SEVERE
ILLNESS
RISK OF
SEVERE
ILLNESS
INFECTION
VACCINE MIMICS
FIRST INFECTION,
BUT DOESN’T
PREVENT A
SECOND ONE
LOW RISK OF
ILLNESS
LOWER RISK
OF ILLNESS
FROM SECOND
INFECTION
... HAS NOT BEEN
VACCINATED
... IS VACCINATED AFTER
THE FIRST INFECTION
...HAS BEEN VACCINATED
BEFORE THE FIRST INFECTION
HOW DENGUE WORKS WHEN A PERSON ...
TRIPPED UP BY A DEVILISHLY
COMPLICATED VIRUS
DENGUE IS MOST DANGEROUS WHEN A PERSON IS INFECTED FOR A SECOND TIME. THE DENGVAXIA
VACCINE RAN INTO TROUBLE BECAUSE IT APPEARED TO ACT LIKE A FIRST INFECTION FOR RECIPIENTS
WHO HADN’T BEEN PREVIOUSLY INFECTED—SET TING SOME OF THEM UP FOR SEVERE SYMPTOMS.
FOR PEOPLE VACCINATED AFTER THEIR FIRST INFECTION, DENGVAXIA IS HIGHLY EFFECTIVE.
111
FORTUNE.COM // DECEMBER 2019
used tires. “It’s beautifully adapted to densely
populated urban environments,” says Jeremy
Farrar, director of the Wellcome Trust, a U.K.-
based charity focused on global health.
Sanofi executives expected that with a
warming climate, the dengue-carrying mos-
quito’s reach would expand, too, spreading the
miserable disease.
Once commonly called breakbone fever,
dengue is painful to endure. (The origin of the
name “dengue” is not certain but is thought
by some to come from the Swahili phrase
ka- dinga pepo, meaning a cramplike seizure
caused by an evil spirit.) Patients suffer debili-
tating spells of headaches, fever, and severe
joint pain that can send them to the hospi-
tal with symptoms that can linger for two
weeks. In the worst cases, patients experience
“plasma leakage,” a life-threatening process in
which the protein-rich fluid of the blood seeps
out of vessels and into surrounding tissues.
Most cases of dengue are not so severe (the
majority are asymptomatic), but up to 5% of
them are—resulting in patients who may in
frighteningly abrupt fashion go into shock or
suffer hemorrhagic fever that can lead to death.
Experts contend no one should die of
dengue. There’s a way to manage cases so that
building of a $398 million plant to produce
Dengvaxia outside Lyon, France. The com-
pany was more than a decade into its dengue
clinical development program, but this was a
next-level, we’re-in-it-to-win-it commitment.
Or gamble, perhaps. At the time, the vaccine
candidate was still in clinical trials and years
from reaching the market. There was a decent
chance it could fail outright—but then, the
potential was enormous. On an earnings call
in 2010, Viehbacher told analysts that the
drug “promises to be potentially the biggest
vaccine we’ve ever sold.”
Preventing dengue, which epidemiolo-
gists call a “neglected tropical disease,” was
an enormous unmet need. There was no drug
to prevent, treat, or cure the illness. And in
the past half-century, as the virus swept from
Southeast Asia to 128 countries, or roughly
half the globe, cases had increased 30-fold.
Dengue is carried by the female Aedes
aegypti mosquito, a resilient, disease-
spreading pest—it also efficiently transmits
yellow fever, chikungunya, and Zika, among
other viruses—that has thrived in the mod-
ern, globalized world. The flying menace
moves around on cargo ships and breeds in
water that collects in, say, plastic waste and
Preventing
dengue
was an
enormous
unme t need.
there was
no drug to
pre vent,
tre at, or
cure this
“neglected
tropical
disease.”
