By Julie Steenhuysen
CHICAGO, Feb 4 (Reuters) - A highly anticipated study of the
first new tuberculosis vaccine in 90 years showed it offered no
added benefit over the current vaccine when it came to
protecting babies from TB infections, a disappointing but not
entirely unexpected outcome, researchers said on Monday.
The vaccine, known as MVA85A, is the most advanced of more
than a dozen TB vaccines now in clinical trials in people, and
scientists are poring over the results to learn why the trial
failed and how the results can inform future studies.
MVA85A was developed by researchers at the University of
Oxford in Britain with support from Aeras, the Wellcome Trust,
the European Commission and the Oxford-Emergent Tuberculosis
Consortium, a joint venture between Oxford and Emergent
Biosolutions Inc.
"Obviously, we all would have liked to see greater
protection," said Dr Ann Ginsberg of Aeras, a non-profit biotech
based in Rockville, Maryland and funded in large part by the
Bill & Melinda Gates Foundation.
The current TB vaccine, known as Bacille Calmette-Guérin, or
BCG, was developed in 1921, and is given routinely to babies in
countries with high rates of TB to prevent severe disease.
However, protection wears off in just a few years, and BCG
does nothing to protect against the most common form of
tuberculosis that invades the lungs of adults and adolescents,
and can be transmitted through coughing and sneezing.
For the study in the British medical journal, the Lancet,
researchers tested the vaccine in nearly 3,000 healthy babies in
South Africa who had already been given the BCG vaccine. Half
also got the new vaccine and half served as the placebo group.
After a follow-up period of about two years, 32 babies in
the MVA85A group got TB compared with 39 in the placebo group, a
modest, but statistically insignificant improvement.
Researchers said the protection seen in the infants was much
lower than had been seen in adults who had tested the vaccine,
and they plan to look more closely to understand why. They did
not provide figures on how well it worked for adults.
Despite the result, the study represents a landmark.
"This is the first efficacy trial of a new TB vaccine since
Bacille Calmette-Guérin, a significant step in itself, and there
is much that we and others can learn from the study and the data
it produced," Helen McShane from the University of Oxford, who
developed the vaccine, said in a statement.
With many other infectious diseases, scientists can rely on
animal models and protective markers in the blood known as
correlates of protection to predict whether a vaccine will work
in people. This is not that case with TB, an ancient disease
that hides out in the cells of their human hosts.
As a result, TB vaccines must be tested in large clinical
trials in people, a large and costly gamble.
Christopher Dye of the World Health Organization and Paul
Fine of the London School of Hygiene and Tropical Medicine, said
in a commentary published with the study that the trial offered
some of the first hard evidence about protection against TB in
people.
"If the history of TB vaccine research teaches us anything,
it is to expect surprises. We need to keep playing this
high-stakes game," they wrote.
Aeras remains committed. It is backing six TB vaccine
candidates, including two others in large-scale trials -- one by
Johnson & Johnson's Crucell vaccines unit and one by
GlaxoSmithKline.
Ginsberg said it would be "a huge mistake for the world to
get discouraged by this and give up." She said TB was "far too
urgent a problem" and the current tools "far too inadequate" to
address the global TB epidemic, which infects 9 million people
annually and kills 1.4 million.
"The one thing that could change the game on the TB epidemic
is to have safe, affordable and effective vaccines," she said.
"We absolutely cannot afford to slow down at all."
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