FDA Panel Backs Shingles Vaccine
Experts Say Vaccine Is Safe and Effective for People Over 60
Dec. 15, 2005 -- An FDA advisory panel backed the approval of the first
shingles vaccine Thursday, though for a narrower group of patients than
manufacturers had sought.
But experts also strongly urged more studies of how the vaccine works in
patients with chronic disease and suppressed immune systems and asked the
agency to require manufacturer Merck to carefully monitor safety if it is
released to the U.S. market.
The vaccine -- known as Zostavax -- is actually a double dose of chickenpox
vaccine. Both shingles and chickenpox are caused by the same virus, called
Shingles usually occurs in older adults and the immunocompromised and is a
reactivation of the chickenpox virus. It can cause chickenpox-like skin blisters that usually appear in a band-like pattern; hence the name
"shingles." The rash can cause severe pain, tingling, and numbness in
some patients that can last long after the visible rash has resolved.
In trials, the vaccine cut the risk of shingles roughly in half for patients
over 60. Patients between 60 and 69 who got the vaccine were nearly two-thirds
less likely to develop shingles than patients who got an inert placebo shot,
but the treatment was progressively less effective as it was used in older
That fact concerned some experts. People over 80 are at greatest risk for
severe pain and chronic nerve pain known as postherpetic neuralgia that can
result from shingles.
Merck sought to sell the vaccine to adults over 50 years of age. But members
of the advisory panel unanimously recommended that the agency reject that bid
because the company did not present clinical evidence that it is safe and
effective in patients under 60.
Bonnie M. Word, MD, an assistant professor of pediatrics at Baylor College
of Medicine and a member of the expert panel, says Merck was asking for "a
leap of faith" concerning use of the vaccine in patients under 60.
"My guess is it will work once the company does the studies but until we
have the studies we really can't comment," says David Markovitz, MD,
another committee expert.
Experts unanimously backed the vaccine as safe and effective in preventing
shingles in patients over 60. Though positive for Merck, the panel made its
recommendation considerably narrower than the company had wanted.
Merck had also asked the FDA to approve Zostavax for prevention of
postherpetic neuralgia in patients who already have shingles, which can linger
for years. The company's data suggested that the vaccine could cut that risk by
nearly 40% overall.
But several experts questioned whether trials showed a strong ability to
prevent neuralgia itself or whether the effect was mostly due to a lower rate
Booster Shot Needed?
Researchers still don't know exactly how the vaccine would be used if the
FDA grants approval. The FDA isn't required to follow the recommendations of
its advisory panel, but it usually does. Merck's clinical study lasted four
years, leaving open questions on whether or not patients may require a booster
shot if the vaccine's effect dips after that time.
Experts also asked the FDA to require Merck to study how the vaccine works
in patients with suppressed immune systems caused by medical treatments or HIV
infection. Those patients are the most vulnerable to debilitating shingles but
are also at the highest risk for vaccine complications.
"The concern is that you're talking about giving this to a universally
large population without adequate safety data, says Gary D. Overturf, MD, a
professor of pediatrics and pathology at the University of New Mexico, and
chair of the advisory committee.
Jeffrey Silber, MD, Merck's senior director of clinical research, tells
WebMD that the company would begin trials with immunosuppressed patients in
2006. The company also plans to continue its study to find out how long the
vaccine's protective ability lasts.
"That question is in the process of being answered but will of course
take several years," he says.