VaxGen
reveals summary of AidsVax data, but results
change from show to show
The
failure of AidsVax to prevent infection
with HIV - in clinical trial results
published in 2003 - triggered an intense
debate about the controversial product
and its manufacturer, VaxGen Inc of
Brisbane, California. Mail to this
website, maintained by Brian Deer, shows that
existing material on a VaxGen-AidsVax
index is read by significant
numbers. This page seeks to
inform the discussion
Below
is material from three different
presentations of apparently definitive
preliminary results of the AidsVax phase
III US trial: (A) February
24, (B) March
19 and (C) March
31. For reasons best known to
the company, the data and its format kept
changing between one showing and the
next, or, in the case of (C)
ethnic categories are switched, making
important comparisons impossible.
[Puzzling time to seroconversion
data for ethnic groups, also
available at this site, was presented at
the first event but mysteriously never
resurfaced.]
(A)
February 24: Presented by VaxGen CEO Dr
Lance Gordon
These
were the data given on the day the
company admitted that the trial had
failed to show overall efficacy, but
claimed that AidsVax had shown astounding
efficacy among US ethnic minorities. The
company made clear that sophisticated
statistical work had been carried out in
consultation with the Centers for Disease
Control. Later it emerged that UNAIDS was
also involved in this statistical work.
(B) March 19:
Presented by VaxGen CEO Dr Lance Gordon
At
the next event - an investors conference
- a different results slide was shown.
This gives much less detail, but the
overall percentages of vaccine efficacy
are the same as on February 24 for the
first three categories ("All
volunteers", "white
and Hispanic" and "black,
Asian and other"), but in
the next three categories ("black",
"Asian" and
"other") the
efficacy has fallen slightly. With so
much data from the first slide absent
from the revised version, it is not easy
to see why this should have happened.
(C) March 31:
Presented by AidsVax inventor Dr Phillip
Berman
At
this event, multiple changes are made in
the presentation of the data, such as in
this new slide giving the overall
figures. Now, in addition to the results
prescribed by the trial protocol
(versions of which are used in A
and B)the company
introduces a new "intention
to treat" (ITT)
category of subject, who have had only
one shot, as opposed to the three shots
in the "per protocol"
groups. This figure (given first) raises
the apparent efficacy of AidsVax from
3.2% (statistically zero), to 5.7% (still
statistically zero, but sounding better
all the time). The confidence interval
for all volunteers is also slightly
different from the first slide.
Broken down by ethnic
group, the (C) March 31
presentation becomes yet more
interesting. The previous binary
conflation of races into BAO
(black-Asian-other) and white/Hispanic
has gone. Now Hispanic volunteers are
moved into a new conflation HBAO
(Hispanic-black-Asian-other). No
compelling reason was given for this
during Dr Berman's presentation, but it
might tend to suggest a line of thinking
that more people than envisaged by the
company on February 24 might be seen as
potential targets for the product.
Multiple variations from previous slides
are also evident in both vaccine efficacy
and confidence intervals.
Discussion of the
company's claims, such as exchanges on
the Yahoo message
board, raised the question
of whether VaxGen's ethnic conflations
represented any credible association, or
whether they had been devised by VaxGen
purely for the purpose of presenting the
statistics in the most
commercially-favorable light.
Time
to seroconversion data can be seen on a pair of
slides from the February 24
presentation.
|
