If an ounce of prevention is worth a pound of cure, a
herpes vaccine could be just the ticket. In fact, the
US-based National Institutes of Health and pharmaceutical
giant GlaxoSmithKline are banking on it with their co-sponsored
Herpevac clinical trial, which is about to launch its
Canadian arm.
Results from an earlier already
completed Phase III study have been encouraging, showing
a 75% reduction in genital herpes in women who received
Herpevac ("There's
no simplex solution... yet," May 30, 2004, Vol 1,
No 11). Dr Iris Gorfinkel, principal investigator in
Toronto, is really excited about those earlier results.
"A 75% reduction is a very attractive number," says
Dr Gorfinkel, a family physician with a long involvement
in clinical and vaccination trials. "It's a huge reduction."
WANTED:
THE HERPES-FREE
The study, which involves a total of 7,500 participants
in a randomized double-blind trial with Herpevac and
the hepatitis A (control) vaccine, has been up and running
for over a year in the US at 35 different sites. In
Canada, the trial will be held at six sites with 175
participants required per site. Canadian recruitment
kicked off in early May for women ages 18 to 30 with
no history of oral or genital herpes. And that's where
it gets complicated.
Although there's been tremendous
interest, the American experience has proven recruitment
to be tougher than expected. Simply put, it's not easy
finding women who test negative for both the HSV1 and
HSV2 antibodies. Dr Gorfinkel says this was as much
a surprise to investigators as it was to participants.
"What we've learned from those [US] sites is that the
seroprevalence rates are higher than we had expected
them to be," she says. "That has been the biggest stumbling
block to this trial to this point."
The trouble is many of the trial
participants had no idea they had the virus. "Seroprevalence
rates in some sites were as high as 50%, which is huge,"
explains Dr Gorfinkel. "It's estimated that up to 20%
of people who have herpes never have any episodes or
manifestations of it."
KNOWLEDGE
IS POWER
With herpes detection flying under the radar to such
a degree, exact statistics are impossible to come by.
Seroprevalence rates in the US are estimated at 1:4
to 1:5, and in Canada 1:5 to 1:6, according to Dr Gorfinkel.
"But we really don't know. There are no real reliable
studies that have undertaken huge numbers of cross sectional
population."
There is, however, an upside for
seropositive women excluded from the trial —knowledge.
And as Dr Gorfinkel stresses, "knowledge is power. It
is power to recognize the disease, power potentially
to prevent its complications," she elaborates. "And
although neonatal herpes is not a common event, it is
such a serious event that should it go unrecognized
it has devastating consequences to the fetus including
meningitis, encephalitis, and blindness in newborns."
Personal benefits aside, the primary
reason given by women for participating in the trials
is to help the greater good. "Their number one answer
was actually: 'I want to help women's health.' That's
the biggest motivator," says an impressed Dr Gorfinkel.
"Their secondary reason is for potential protection
personally against the herpes virus."
Either way, the passion is there,
both from investigators and potential participants,
and Dr Gorfinkel encourages Canadian physicians to get
the word out to their patients who fit the parameters
(contact details are at the end of the article). Due
to a 50% screen failure rate, she estimates at least
350 women would need screening to find 175 suitable
candidates.
WHERE
ARE THE MEN?
And what of men in this equation? The initial Phase
III trial that looked at 7,440 men and women showed
no efficacy in men. "We believe it may be related to
cervical mucous and vaginal mucous immune differentials
between men and women, or chromosomal differences, but
we don't know for sure why," says Dr Gorfinkel, adding
that vaccination of women will indirectly help men by
reducing disease loads throughout the community of women,
thereby exposing fewer men.
Although a herpes cure continues
to elude, Dr Gorfinkel is passionate about prevention
for what many consider merely a 'nuisance disease.'
"If this trial should show good efficacy and safety,
there's a good chance it will go on to be an approved
vaccination. And that has huge implications for women's
health."
Canadian
trial sites are in Toronto, Halifax, Beauport, QC, Surrey,
BC, Winnipeg and Edmonton. For information on the Herpevac
trial for women visit www.herpevac.com.
Toronto area physicians may obtain additional information
or refer interested patients to Dr Iris Gorfinkel at
416-486-8444.
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