Once a month, at around 3pm, Dr Donald Francis, president of the VaxGen corporation, boards a 747 at San Francisco airport for an 18-hour flight to Bangkok. The route is unpopular - with maddening stops in Seoul, Hong Kong or Taipei - and he insulates himself in a business class window seat with earplugs, eye-mask and face-cream. The tedium drives him crazy, but he doesn't sleep much. His adrenaline levels stay high. Speculations loop like a tape through his head: "What if I do? Supposing I don't?"
He's 57, but looks ten years younger, with blue eyes and an animated style that makes people think that he's gay. When they grasp that he's not (married twice, two sons) the next thing they guess is that he works in show business; say, music or motion pictures. Boyish, fit, articulate, charismatic; he's a person you'd choose to sit next to. But he's a doctor and scientist in the gruesome field of Aids, so demons lurk behind the mask.
I couldn't wait to meet him. We've something in common: we've followed the epidemic since the start. I reported on the first known death in Britain, in December 1981. He was the first to alert America's blood banks, arguing that a virus was to blame. In Randy Shilts's 1987 Aids history, And The Band Played On, Francis storms across 76 pages, warning, demanding, lambasting. In the movie of the book, starring Richard Gere and Anjelica Huston, he's played by Full Metal Jacket's Matthew Modine. He's ER meets JFK.
A man with his record might have taken it easy, sure he'd done enough. In the 1960s, as a young MD with the American government's epidemiology service, the Centers for Disease Control (CDC), based in Atlanta, he was dispatched to India to help eradicate smallpox: a triumph against infectious illness. In the 1970s, while studying virology at Harvard, he was rushed to Sudan by the World Health Organisation - the WHO - to investigate the first outbreak of ebola. In the 1980s, he led trials in Phoenix of a successful vaccine against another killer, hepatitis B.
But for him these achievements merely judder like turbulence; they remind him of what's still to be done. When he slips into Bangkok the following morning, his destination is Taksin Hospital, by the Chao Phraya river, a corroded-concrete and grimy-glass hulk full of poor people patiently waiting. He goes to the second floor and through a pair of glass doors, where the atmosphere transforms. There are maroon carpets, soft furnishings and secretaries in beautiful dresses. A sign inside says: "Bangkok Aids Vaccine Evaluation Group". The VaxGen experiment.
People laughed when he declared - seven years ago - that he would be first with a shot against Aids. After 20 years as a fireman with the CDC, everybody said that he couldn't focus on such an intricate project. Although he'd set-up an Aids lab back in 1983, ten minutes at a bench would have him yawning and twitching. He preferred khaki shorts to white coats.
Since the human immune deficiency virus was discovered in 1984, moreover, it has been the definitive white coat challenge - and quite different from his previous foes. Unlike smallpox - an easy target- HIV kills some of the very cells (so-called T-helper cells) which are fundamental to our immune system defences. Unlike ebola, a rare disease, HIV has slayed 14m people and infected another 35m. And unlike hepatitis B virus, which is quite stable, HIV is a so-called "retrovirus", with its genes coded in ribonucleic acid (RNA), and changes so much with each replication that it breeds an infinity of strains.
When Francis was at medical school in the 1960s, a virus was a virus, with maybe three strains, like polio. Vaccines were easy. But such is HIV's frenetic shape-shifting that each infected person harbours an astonishing swarm of strains, totalling about 1 billion, all slightly-different, virions. Scientists lump them into two types (HIV-1 and HIV-2), three groups and ten subtypes. Thousands of strains are studied. At med school he learnt that parasites evolve to live in harmony with their hosts. But HIV is so new and unstable in humans that it may evolve to become a quicker killer, or be more infectious. The truth is, nobody knows.
Cleverer doctors and scientists than him have got lost in this terrain. So far, some three dozen would-be vaccines have been tested in labs, animals or a few individuals, but none has done any good. Vaccines work by priming our immune systems - including antibodies and T-cells - so that they will be ready for action if a bug comes along. But so far every attempt to accomplish this with HIV has either proven dangerous or to have no effect. Some experts say that nothing will work.
Francis crosses the Pacific with an approach to the problem that sounds beguilingly simple. The VaxGen experiment is with a product - brand-named AidsVax - that mimics part of the viruses skin, or envelope. By inoculating healthy people with a manufactured clone of this part - a sugary "glycoprotein" called "gp120" - antibodies are supposed to be primed to protect in the event that sex, blood or drug misuse causes the virus to later intrude.
At Taksin Hospital he fine-tunes the experiment - a "placebo-controlled double-blind trial" - so far the only full-scale Aids vaccine trial ever. On 24 March, the first of 1,250 HIV-negative Thai volunteers started on a course of seven six-monthly shots. Another 1,250 are getting an inactive placebo. Who is getting what is concealed in codes, and any difference in the numbers who later become HIV-positive should reveal if the product works.
Francis meets with Dr Kachit Choopanya, his principal investigator. In silk suits and gold-rimmed glasses, Kachit, 65, controls 17 Bangkok drug dependency clinics, chosen to take part by Francis's old friends at the CDC and WHO. Heroin misusers are top of the HIV risk-list, due to poverty-driven needle-sharing. If they can be protected, the agencies reason, then you, I, or anyone can. "If the VaxGen vaccine can create immunity in humans, then we can solve the whole problem," Kachit declared on the day of the first jab. A 27-year-old heroin addict was equally upbeat. He said: "I believe the trial could bring great benefit to mankind."
There's a similar impression at a high level in America that history may be about to be made. The US government's National Institutes of Health and its Food and Drug Administration, both in Maryland, are backing the experiment. So are officials of the World Bank in Washington and United Nations agencies. And so is the principle lobby group: the International Aids Vaccine Initiative. The group's president, Dr Seth Berkley, said: "We applaud VaxGen."
Francis basks in these endorsements. He settles on the thought that he'll do it. VaxGen is one quarter owned by Genentech Inc, a medical biotechnology leader. Genentech is a subsidiary of Hoffman-La Roche, the Swiss pharmaceutical colossus. All are poised for full-scale production. When shares in the company were launched on the New York Nasdaq market at the end of July, they jumped from $13 to $26. He banks on a license for a crash programme of inoculations like the world has never seen.
But when he flies in from San Francisco, he can never quite quell his anxieties. In his files are papers which suggest that AidsVax can't really work. And he's familiar with scientists who warn of possible hazards on a globally catastrophic scale. His vaccine may make it into millions of people. The profits could buy Bangkok. But the momentum behind the experiment could turn out to be one of medicine's greatest mistakes.