Pornchai Kittiwongsakul/Agence France-Presse — Getty Images
A patient receives medical treatment at the AIDS hospital in Bangkok, Thailand.
By DONALD G. McNEIL Jr.
Published: June 12, 2013
Drug-injecting addicts who took a daily antiretroviral pill were half as
likely to become infected with H.I.V. as those who did not, a major new
study has found, providing the final piece of evidence that such
treatments can prevent AIDS in every group at risk. Earlier clinical
trials showed that the therapy can sharply reduce the risk of H.I.V.
transmission from mother to child, and in gay and bisexual men and
heterosexuals.
“This provides the totality of the evidence that the drugs used to treat
the infection are also very effective at preventing it,” said Dr. Salim
S. Abdool Karim, a prominent South African AIDS researcher who wrote a
commentary in The Lancet, which published the new study on Wednesday.
The accumulating evidence from clinical trials means antiretroviral
drugs are increasingly seen as another in the arsenal of weapons to
prevent AIDS, along with condoms, abstinence and fidelity; early
antiretroviral treatment; male circumcision in Africa; microbicide gels;
and other options.
The formal results of the study, which involved 2,400 drug users in
Thailand, showed that taking tenofovir pills — a therapy known as
pre-exposure prophylaxis, or PrEP — reduced infections by 49 percent.
Addicts who took the pills regularly, based on measures of tenofovir in
their blood, did much better: They were 74 percent less likely to become
infected.
“This is an exciting day,” said Dr. Jonathan Mermin, director of H.I.V.
prevention for the Centers for Disease Control and Prevention in
Atlanta. “This culminates a decade of PrEP research.”
Prophylaxis usually involves taking a daily pill of tenofovir or
tenofovir plus another drug, but can also include antiretroviral-laced
vaginal gels used before sex and the use of various antiretroviral drugs
by infected mothers just before they give birth.
The potential impact of the treatment for drug addicts is greatest in
Eastern Europe and Central Asia, where they account for up to 80 percent
of infections. Many countries in those regions, for religious and
political reasons, outlaw proven tactics like handing out clean needles
or offering methadone or other needle-free opioid substitutes.
About 10 percent of the new infections in the world — and about 8
percent of those in the United States — are thought to result from
needle sharing.
The new five-year study was run by Thai researchers with C.D.C. support
through 17 Bangkok drug-treatment clinics. Addicts are notoriously
unreliable about keeping clinic appointments and have been known to sell
even lifesaving drugs, so the participants were offered modest payments
to take their daily pills under the eyes of a nurse. They got $8.75 for
each month they stayed in the trial, plus $8.75 for each week they
showed up all seven days, plus $1.90 each day they appeared. Those who
came in only monthly were paid to keep drug-use diaries.
“We should be under no illusions that these were real-world settings,”
said Mitchell Warren, executive director for AVAC, an organization that
lobbies for AIDS prevention.
On paper, 87 percent of all drugs were scheduled to be taken daily under
observation, but some patients were much more consistent than others;
women and addicts older than 40 did better.
Now that it is clear that the medications work, Mr. Warren said, new
studies must work out how best to motivate unpredictable drug users to
take them.
Dr. Julio Montaner, a University of British Columbia AIDS researcher who
works with a large addict population in Vancouver, said the news that
the therapy worked among drug users was “all very good and dandy — and a
new piece to the puzzle.”
But he said he worried that it would compete for limited government
health budgets with tactics that he were already proven: clean needles,
methadone and test-and-treat, which involves hunting aggressively for
all who are infected in a city and putting them on antiretroviral
treatment immediately, which makes them 96 percent less likely to infect
anyone else.
But Dr. Mermin of the C.D.C. said: “I think we’ve moved beyond
competition between prevention and treatment. Even this is not for
everybody.”
The United States is setting up studies, he said, to see which
anti-H.I.V. tactics work best in different neighborhoods and different
risk groups.
The new study may affect individual doctors’ decisions. For example, a
doctor with an uninfected patient known to inject drugs might choose to
put that patient on daily tenofovir, just as some doctors do with
uninfected but promiscuous gay male patients, or uninfected patients
with infected regular sex partners.
Exactly how the tenofovir protected the participants cannot be known,
Dr. Karim pointed out, because many addicts both share needles and sell
their bodies to get money for drugs, so they engage in two risky
behaviors.
Given how fast AIDS shot through various risk groups when it first
appeared in the 1980s, researchers have long assumed that injecting
blood and sharing needles was the riskiest behavior, followed by anal
sex, then vaginal sex — but there is little data to prove that.
For that reason, some researchers thought it unlikely that pre-exposure
prophylaxis would protect drug addicts, and they were pleasantly
surprised it worked fairly well.
Exactly how well it works in any risk group depends on how study results
are analyzed, but it seems to be roughly as protective for drug users
as it is for gay men, and about as protective as circumcision is for
heterosexual men in Africa.
According to the C.D.C., when study results are adjusted to include only
participants who took their pills most of the time, the protective effects are 92 percent for gay men,
nearly 90 percent for couples in which only one partner is infected, 84
percent for heterosexual men and women, and about 70 percent for drug
injectors.
Two trials done in heterosexual women, known as Fem-PrEP and Voice,
were stopped early because women receiving drugs and those given
placebos were getting infected at similar rates. Later analysis of the
results showed that many of the women had not been taking their drugs.
Some said they did not believe they were at risk, and others said that
if they had bottles of antiretroviral medicines in their homes, their
families and potential lovers would assume they were infected and shun
them.
But single heterosexual women in another trial, conducted in Botswana and known as TDF2, were protected.
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