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FORTUNE.COM // DECEMBER 2019
even the most severely ill recover, but that re-
quires early detection and involves close mon-
itoring and maintenance of a patient’s fluid
levels over a period of days. That’s not easy for
resource-strapped health systems, especially
during outbreaks when dengue patients pile
up in hospital wards. For that reason, dengue
kills about 20,000 people a year.
Given all that, Sanofi expected governments,
not to mention donors like the Gates Foun-
dation and GAVI, an international vaccine
alliance, to happily shell out dollars to prevent
the disease. But the potential market was
even bigger than that. Viehbacher envisioned
that Dengvaxia could one day be a vaccine for
everyone—not just for the people who live in
dengue-endemic countries but also for those in
rich, Western countries who travel to them.
That was exactly the sort of game-changing
product Sanofi’s new CEO needed in order to
transform the storied but doddering French
pharmaceutical firm. Three of Sanofi’s top-
selling drugs were soon to lose patent protec-
tion—and with them, a good chunk of the
company’s revenues.
Viehbacher himself symbolized change. The
German-born Canadian was the first non-
Frenchman to helm the company (which this
year ranked No. 288 on the Fortune Glob-
al 500), and many hoped he’d rev up Sanofi’s
slow-moving and rigidly hierarchical culture.
(Viehbacher, who did not respond to requests
for comment on this story, was ousted in 2014.)
Sanofi had grown into one of the world’s
largest pharmaceutical firms through acquisi-
tions. But it traces its history back to the days
of Louis Pasteur, the renowned French scientist
who, among other things, invented the rabies
and anthrax vaccines. He founded the Pasteur
Institute, the respected biomedical research in-
stitute—part of which became Sanofi Pasteur,
Sanofi’s $6-billion-in-revenue Lyon-based vac-
cine business. Today Sanofi Pasteur produces
much of the world’s supply of inoculations
against flu, polio, and meningitis. Viehbacher
saw huge potential in the business.
Backed by Viehbacher, the dengue vaccine
became a marquee project for the company,A child in the
Philippines
being injected
with Sanofi’s
Dengvaxia vac-
cine in April 2016
as part of the
government’s
drive to vac-
cinate 1 million
schoolchildren.