By Betsy McKay in Atlanta, Preetika Rana in Hong Kong and Noemie Bisserbe in Paris
Sanofi SA's recent disclosure of safety problems with the
world's only approved vaccine against the viral infection dengue
has complicated efforts to contain a growing global epidemic and
could delay potential new vaccines, public-health experts said.
Late last year, the French pharmaceutical giant said its
Dengvaxia product, first approved for sale in 2015, could in some
cases worsen rather than prevent symptoms of the debilitating
tropical disease. It was a frightening finding, and a setback for
scientists who have spent decades and hundreds of millions of
dollars trying to develop an immunization against dengue, a
mosquito-borne virus that each year infects an estimated 390
million people in tropical regions world-wide.
Now, international health officials say Sanofi's troubles could
fuel public distrust of vaccination and lead to regulatory or
political hurdles that developers of new dengue vaccines such as
Takeda Pharmaceutical Co., Merck & Co., and GlaxoSmithKline PLC
must overcome, even though their vaccine candidates differ
substantially from Sanofi's.
"There will be greater scrutiny now," said Joachim Hombach,
executive secretary of the Strategic Advisory Group of Experts on
Immunization, or SAGE, which advises the World Health Organization.
Regulators, Dr. Hombach said, may require several additional years'
worth of data on a vaccine's performance before allowing companies
to market their dengue vaccines.
Lawmakers in the Philippines, where more than 800,000 children
were vaccinated in a government-led immunization drive, have called
for stricter reviews of drugs intended for mass use.
Future vaccine candidates will have to be tested carefully,
Sanofi said. "Regarding the impact on other research efforts, we
cannot know for sure, " a company spokesman said.
Of the people infected each year with dengue, about 96 million
develop a flulike illness, sometimes called breakbone fever for the
excruciating muscle and joint pain it can produce. About two
million cases of dengue a year are severe, with internal bleeding
or shock, and about 20,000 people die. Nearly four billion
people--more than half of the world's population--are at risk of
dengue infection.
The fallout from Dengvaxia "does impact, overall, the dengue
field and the perception of dengue vaccines," said Rajeev Venkayya,
who heads the vaccines business unit of Takeda, whose dengue
vaccine is in a late-stage clinical trial involving more than
20,000 participants.
"We do not think this is going to be a showstopper in any way or
form," said Anthony Fauci, director of the National Institute of
Allergy and Infectious Diseases. He cautioned, however, that
Sanofi's problems mean "clearly there's going to be not as smooth a
trip." NIAID's dengue vaccine candidate is in a late-stage clinical
trial involving 17,000 participants in Brazil.
"We should not give up on a dengue vaccine," Dr. Fauci said.
"It's too important a disease." The NIAID vaccine has been licensed
to several companies, including Merck, which said it plans to start
its own trial this year.
Developing a vaccine is challenging: Four types of dengue virus
can cause disease, and infection with one doesn't provide immunity
to the others. Instead, an infection with one type increases the
risk of severe dengue when someone is infected a second time, with
a different type of the virus. Subsequent infections are less
concerning because a person's immunity is broad by that point,
scientists say.
Sanofi said in November that Dengvaxia could worsen symptoms in
people who never had the disease. The vaccine, in effect, could
mimic an initial infection in those people, increasing their risk
of developing a severe form of dengue if they were infected
later.
The government of the Philippines last month launched an
investigation into its immunization program and Dengvaxia's
possible link to the deaths of at least three children. The
nation's health secretary said Thursday that regulators had
temporarily suspended the vaccine's license and separately fined
the company $2,000for failing to meet some post-marketing
requirements.
Sanofi stopped producing Dengvaxia and said it would take a $119
million charge in the fourth quarter. The company said last month
it would keep selling the vaccine, which it says is safe for people
who had a prior dengue infection.
To avoid Sanofi's problem with its vaccine, new candidates must
provide balanced protection against all dengue types, said Duane
Gubler, chair of the Global Dengue and Aedes-Transmitted Diseases
Consortium and an emeritus professor at Duke-NUS Medical School,
who has consulted on dengue vaccines with Sanofi, Merck and
Takeda.
NIAID's vaccine induced an immune response in tests against all
four dengue types, individually and together, said Anna Durbin, a
professor at the Johns Hopkins Bloomberg School of Public Health
who led U.S.-based trials on the vaccine. Results from the clinical
trial in Brazil could be available within the next year, Dr. Fauci
said.
In studies, Takeda's dengue candidate demonstrated a "sustained
antibody response" against all four dengue types in people
regardless of previous dengue exposure, Dr. Venkayya said, adding
results from its current trial are expected late this year.
Researchers drew pre-vaccination blood samples from all
participants in late-stage trials of both vaccines, to determine
whether they were infected with dengue before--a step Sanofi didn't
take that made it difficult to pinpoint the problem with its
vaccine.
GSK conducted an early-stage trial on one vaccine candidate, but
now says it is trying "to identify the composition of a vaccine
that could really induce a balance in response" against the four
dengue types, though this work is at a "very early stage."
Write to Betsy McKay at betsy.mckay@wsj.com, Preetika Rana at
preetika.rana@wsj.com and Noemie Bisserbe at
noemie.bisserbe@wsj.com
(END) Dow Jones Newswires
January 07, 2018 08:14 ET (13:14 GMT)
Copyright (c) 2018 Dow Jones & Company, Inc.
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