The research is the biggest and longest assessment into the effectiveness of highly active anti-retroviral therapy (HAART) — the combination of powerful drugs that suppresses, but does not cure, the human immunodeficiency virus (HIV).

A total of 9803 patients were enrolled in 70 HIV centres in Europe, as well as in Israel and Argentina, for the EuroSIDA study, details of which are published on Saturday's issue of The Lancet, the British medical weekly.

The recruitment unfolded in three stages: in 1994-5, before HAART was introduced; in 1996-1997, when HAART first started to be available; and 1998-2002, when new drugs joined the HAART arsenal and doctors became smarter about how to use these medications.

Mortality from Aids fell sharply between the pre-HAART and late-HAART era, the researchers found.

The biggest improvement was among whose immune systems had been ravaged by HIV and among those whose systems were in relatively good shape. Among these two groups of patients, the death rate fell by half and in one spectacular category by two-thirds.

There was no significant reduction in the death rate among those whose immune defences were in an "intermediate" state, defined as between 101 and 350 CD4 immune cells per microlitre of blood.

Another remarkable finding was that progression from HIV infection to full-blown AIDS also fell sharply between the pre- and late-HAART era, by between a quarter and a half, regardless of the CD4 count.

Overall, the average CD4 count amongst volunteers doubled in the eight years between when there was no HAART and when the enhanced HAART regime was available.

The introduction of HAART initially spawned feverish hopes that AIDS had been slain, for many people with HIV reported a big improvement in their health and the death rate fell by a fifth within the first two years.

Then came a series of disappointments. Evidence emerged that the drug combination was able to reduce HIV to undetectable levels, but the virus holed up in a reservoir in the body — presumed to be the lymph glands — and charged out as soon as the medication was stopped.

In addition, the drugs were found to have toxic side effects among some patients and there were worrying signs that the fast-mutating AIDS virus was building resistance to them.

Despite all this, the big progress initially seen after HAART's introduction "has been sustained," the authors say.

"Potential long-term adverse effects associated with HAART have not altered its effectiveness in treating Aids."

Controversy has swirled around HAART, not for its use as a clinical weapon against AIDS, but its lack of availability to poor countries, which account for the overwhelmingly majority of people with HIV.

It took some five years after HAART was introduced in the West for pharmaceutical giants to make big cuts in the drugs' pricing regimes for poorer countries.

Those reductions, driven by intense pressure by lobby groups, have in some cases been joined by offers to offer the drugs for free in the poorest, worst-hit countries.

The EuroSIDA study was led by Amanda Mocroft, an expert in health and population at the Royal Free and University College Medical School, London.

AFP