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To their surprise, the
researchers said such a vaccine would increase death rates in countries
where the AIDS epidemic was either low or moderate, while the same vaccine
would reduce greatly the death rates in nations where AIDS was rampant.
"The exact same
vaccines could be beneficial in one country, but detrimental in
another," Dr. Sally Blower, professor of biomathematics and a member
of the UCLA AIDS Institute, said in a telephone interview.
Blower said an
attenuated vaccine might prove worthwhile only in developing countries
facing perilous transmission rates, such as those in sub-Saharan Africa.
"If you use such a vaccine, for example, in the United States, you
would definitely make things much, much worse," she said.
Such a vaccine could be
instrumental in fighting the disease because it generates a strong
immunity, but it could also cause AIDS in some vaccinated people because of
its use of the live virus.
Blower, the study's
principal investigator, described a "Catch-22" situation for
public health officials around the world if researchers fashioned an AIDS
vaccine using a live virus.
"The vaccines have
the potential to do a great deal of good, but they also have the potential
to do harm. That's the essence of the Catch-22 problem," Blower said.
"You can develop
very effective vaccines. But they may well be the ones that are the least
safe. There may be a trade-off that people will have to consider between
efficacy and safety once these vaccines have been developed."
The development of any
such vaccine is still years away. Live attenuated vaccines have been used
in the past to control such diseases as polio, smallpox and measles.
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