Miracle HIV vaccine continues to elude researchers

Where's the vaccine?


Twenty years after Aids became an unwelcome addition to the worldwide vocabulary, breakthroughs in treatment of the virus represent "maintaining the status quo."

Dr Mark Thomas, a specialist in Aids and infectious diseases at the University of Auckland Medical School, points out that "to an infected person that's important."

Important, yes, but a long way from the miracle vaccine.

Last month, Bill Gates pledged $US100 million ($223 million) to the search for such a vaccine. In response, internet portal company Yahoo! promised $US5 million over three years for what will be called the International Aids Vaccine Initiative.

The million-dollar question is whether throwing money at what Gates has called "an unbelievable market failure" will help to stem a pandemic in which more than five million people contracted the Aids virus last year.

A big obstacle is the virus' mutation rate. In an infected person not on treatment, every possible mutation is produced every 24 hours. Most of these mutations die, but the virus has already managed to spawn more than a dozen subtypes. The next big question is: would a single vaccine be effective?

A vaccine which works well on a person infected in New York won't necessarily work on a person infected in Soweto, says Dr Thomas.

What's on the vaccine horizon?


The first vaccine candidate designed for Africa will enter clinical trials in Nairobi soon. Volunteers for phase one of the trial have already been screened. VaxGen, a Californian-based company, is conducting the first large-scale tests in humans of a possible vaccine. An interim analysis of the tests, which involve 8000 volunteers across three continents, is scheduled for November.

Dr Thomas says that any successful vaccine is unlikely to work like those for measles or chicken pox. It's not going to be a one-jab wonder. The vaccines scientists are optimistic about are more complicated injections which involve delivering a series of vaccines which could work in different ways to boost the immune system.

What has changed in recent treatment of HIV infection?


Treatment now starts later. In the past, treatment was started when the T4 (or CD4 or T cell) count dropped below 500. Now treatment is likely to start when the count is 350 to 300. It became apparent, says Dr Thomas, "that the drugs are horrible and people can't take them reliably for long periods of time. It doesn't look as if there are advantages to starting treatment early."

The period between infection and treatment is now between five and 10 years.

A breakthrough in drugs has been a combination of two of the AZT-like drugs (the first, and still most commonly used, generation of drugs used to treat HIV-infected people). This is regarded as a breakthrough because a major problem with the drugs has long been the large number of pills taken daily - between 15 and 20 - and at precise times of the day. If people don't take on average at least 95 per cent of their pills on time (and not everyone can take them) in any month, the virus starts bouncing back - resistant to one or more of the drugs.

On January 1, Pharmac announced that it would pay for two new drugs: Efavirenz and Abacavir. Again, the advantage is that patients take fewer drugs with fewer side effects.

What's in the medicine cabinet of the future?


A new class of drug to treat those people whose infection has become resistant to the present ones.

What does it cost?


$300 to $500 per drug per month. Those with HIV are normally on three drugs at a time, so the cost can reach $1500 a month.

Four tests a year to determine how much virus is present in the blood and T-cell counts cost $1200 a year.