New data on an
experimental AIDS vaccine that failed to work shows
volunteers who got the shots were far more likely to get
infected with the virus through sex or other risky
behavior than those who got dummy shots.
The new details,
released Wednesday by drugmaker Merck & Co., don't
answer the crucial question of whether failure of the
vaccine also spells doom for many similar AIDS
vaccines now in testing. Researchers weren't sure why
more of the vaccinated volunteers wound up getting HIV than
those who got dummy shots.
''One of the
possibilities is that the increase in the number of
infections was related to the vaccine,'' meaning it could
have made people more susceptible to HIV infection,
said Keith Gottesdiener, vice president of clinical
research at Merck Research Laboratories. He couldn't
say how likely that was but said other factors, even
coincidence, could be the explanation.
Merck, based in
Whitehouse Station, N.J., announced on September 21 that
it was stopping the study because the vaccine didn't work.
It was a stunning setback in the push to develop an
AIDS vaccine. Merck's vaccine was made from a common
cold virus with three synthetic HIV genes tucked
inside. It was designed to stimulate the immune system to
kill any HIV-infected cells encountered in the future.
researchers found that volunteers with pre-existing immunity
to this particular cold virus were much more likely to get
infected with HIV if they got the AIDS vaccine than if
they got the dummy shot.
people, mostly gay men and female sex workers, had
volunteered to get the experimental vaccine or dummy
shots. All were warned to protect themselves from AIDS
At the time the
study was halted in September, Merck said 24 of 741
volunteers who got the vaccine in one segment of testing
later developed HIV; 21 of 762 participants who got
dummy shots also were infected.
New data released
Wednesday showed that to date, 49 of 914 vaccinated men
became infected with HIV, compared with 33 of the 922 men
who got dummy shots. Only one woman and a small number
of heterosexual men were infected.
''In my mind,
this doesn't damn anything,'' Anthony Fauci, head of the
National Institute of Allergy and Infectious Diseases, said
of the vaccine's failure. ''It tells you you need to
be very careful with every aspect'' of vaccine design
and testing. The international testing was partly
funded by the National Institutes of Health.
Merck's head of
medical affairs for vaccines, Mark Feinberg, said it
could be a few years before further data mining and results
of other drugmakers' vaccine tests clear up the
Wednesday, Merck shares fell $1.79, or 3.2%, to $54.20 amid
a broad decline in the stock markets. (AP)