Only 15 percent of children who need treatment are receiving antiretroviral (ARV) drugs, the International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention, the world's largest gathering on AIDS and science, heard on Wednesday in Sydney, Australia.

Treating HIV positive babies has always been difficult: doctors have a very limited choice of drugs at their disposal, and around half of children living with the virus die before their second birthday.

Caring for them is complicated by the fact that the immune system is not fully developed in the first year of life, making these children particularly vulnerable to rapid HIV progression and death.

Existing guidelines suggest that HIV-positive infants should only receive ARVs after they show signs of illness or a weakened immune system, but study findings presented at the conference on Wednesday suggest that the early treatment of babies living with the virus helps them live longer.

"This is the first randomised clinical trial that shows that infants treated before three months of age will do better than infants who have their treatment delayed," said Dr Elias Zerhouni, director of the US National Institute of Health (NIH), which sponsored the trials.

The Children With HIV Early Antiretroviral Therapy study is being carried out in South Africa by the Comprehensive International Programme of Research on AIDS (CIPRA), a division of the NIH.

The trial started in July 2005 and was designed to continue through 2011, but a review of early data last month revealed a significant increase in survival among infants who had received immediate ARV therapy: 96 percent of the children were alive, compared to only 84 percent of those in the control group.

Avy Violari, of the University of Witwatersrand, South Africa, who led the trial, told conference delegates that starting antiretroviral therapy before 12 weeks of age reduced early mortality by 75 percent.

The next step?

The public health implications are significant. "We think that the data is compelling. It is a very strong result, and it is now up to policymakers to decide what to do with it," Dr James McIntrye, head of CIPRA, told IRIN/PlusNews.

The findings, which have already been released to the UN World Health Organisation, should prompt experts to consider changes in standards of care in many parts of the world, the NIH said in a statement.

However, Annette Sohn, professor of Paediatric Infectious Diseases at the University of California, San Francisco, cautioned that "the goal of treatment in children must be balanced between halting the effects of the HIV disease and the long-term effects of antiretrovirals on a developing child".

Children who begin taking life-prolonging ARV medication earlier will likely be forced to switch to more difficult and expensive second- and third-line regimens as the virus becomes resistant to first-line drugs. "What is the future for those children already on second-line drugs at the age of five?" Sohn wondered.

Lack of child-friendly formulations

A minority of HIV-infected children have access to ARVs, because the drugs are still only available in adult formulations. Pharmaceutical companies have not yet developed fixed-dose combination treatments in dosages appropriate for children, and physicians must often portion out a cocktail of three separate adult-dose medicines as the child grows.

To determine correct paediatric doses effectively, caregivers should ideally use the three drugs according to the surface area of the child - a number obtained by a complicated formula of multiplying the child's weight by its length, dividing by 3,600, and then taking the square root of that figure.

This kind of calculation is often impossible, and health facilities are forced to simplify the process, which means setting dose standards - including combinations of syrups and crushed or broken pills - by the weight of the child.

There is a risk of HIV-positive children sometimes being overdosed, with increased side effects, but overdosing is generally preferred to underdosing, which can gradually lead to resistance to the medication.

"We need to expand treatment coverage, and to do that it is essential to have more and better paediatric antiretroviral formulations," said Sohn.