UPDATE: Merck Study: No Significant Safety Risk For Shingles Vaccine
May 06 2010 - 04:34PM
Dow Jones News
A new study designed to answer questions about the safety of
Merck & Co.'s (MRK) shingles vaccine suggests it doesn't
significantly increase the risk of serious side effects.
The Merck-sponsored study of nearly 12,000 people ages 60 and
older did find a higher rate of serious adverse events among
recipients of the vaccine, Zostavax, than among those who got a
fake shot, or placebo. However, the difference wasn't statistically
significant, which means it could have been due to chance.
The Zostavax "and placebo groups had similar safety profiles"
both in the six weeks and six months following vaccination,
according to a summary posted online by the Journal of the American
Geriatrics Society. Results also have been posted on the online
government database clinicaltrials.gov. Full results are scheduled
to be presented May 13 at the geriatrics society's annual
scientific meeting in Orlando, Fla.
A Merck spokeswoman said the company couldn't discuss the safety
results until they're presented at the medical conference.
Zostavax, which Merck started selling in 2006, was shown in an
earlier study to reduce the occurrence of shingles among people 60
and older by about 50%. Shingles is a nerve and skin disorder that
results from reactivation of the virus that causes chickenpox;
shingles also can lead to a painful condition called postherpetic
neuralgia.
Previous clinical-trial data have sent mixed signals about
Zostavax's safety. A large study to prove Zostavax's efficacy,
which was published in The New England Journal of Medicine in 2005,
found that the overall rate of serious adverse events among vaccine
recipients was similar to those on placebo--suggesting the shot was
safe.
But a pre-specified safety analysis of a smaller group of
participants in the same study found a higher risk of serious
events, including heart-related problems associated with Zostavax.
The prescribing label for Zostavax warns about this apparent
risk.
Some researchers have said the safety risk in the subgroup study
was an aberration because there was no pattern to the adverse
events that would indicate the vaccine caused the problems. Still,
some doctors have remained cautious about recommending the
shot.
To address the uncertainty, Merck conducted a new study
specifically designed to assess safety. The trial enrolled and
tracked nearly 12,000 people in the U.S., Canada and Europe between
September 2007 and January 2009. Roughly half received Zostavax and
the other half got placebo shots.
At 42 days post-vaccination, the Zostavax recipients experienced
84 serious adverse events, which were defined to include those
resulting in death, hospitalization, cancer and other events. There
were 67 such events in the placebo group. The risk of serious
adverse events among Zostavax users was 1.4%, versus 1.1% in the
placebo group, a statistically insignificant difference.
At six months following vaccination, some 340 serious adverse
events were reported in the Zostavax group, a rate of 5.7%, versus
300 in placebo, or 5%, also a statistically insignificant
difference.
There were 24 fatal serious adverse events in the Zostavax group
and 17 in the placebo group, but researchers didn't deem any of the
deaths to be vaccine-related. One doctor said he still has concerns
about a potential safety risk with Zostavax. C. Bernie Good,
professor of medicine at the University of Pittsburgh, said he was
concerned about the higher number of deaths and serious adverse
events in the Zostavax arm, even though the difference was
statistically insignificant.
Good, who treats older patients, said the new study doesn't
change his policy of not routinely recommending the vaccine.
"Rather I will discuss both the absolute benefits, with the
absolute harms that we have from both studies," he said. "Based on
that information, some patients will choose the vaccine, and others
will decide to pass on it. Neither patient will be wrong in their
choice."
Merck's Zostavax sales declined 11% to $277 million for 2009, as
a manufacturing snafu constrained supplies. Merck says it's working
to resolve the supply problems, but it has put off launching
Zostavax outside the U.S. until 2011.
Merck also is seeking to widen the market for Zostavax. It
expects to file for regulatory approval sometime this year to
market the vaccine to people ages 50 to 59, an age group for which
it's currently not approved, even though risk for shingles begins
to rise substantially at age 50.
Merck shares dropped 3.6% to $34.32 Thursday amid a broader
market downturn.
-By Peter Loftus, Dow Jones Newswires; 215-656-8289;
peter.loftus@dowjones.com
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