he Asia-Pacific region is the world’s largest and most diverse in terms of geography, populations, cultures, and political and economic systems. Stretching halfway across the globe, from Iraq to Tahiti, it is home to the world’s most populous countries—China, India, Indonesia—as well as some of the smallest and most isolated, the island states of the South Pacific.

The region is also home to a belated, but now burgeoning AIDS epidemic, as several meetings and reports in late 2001 made clear. About 7.1 million Asian people are living with HIV/AIDS, over one million of them infected just within the past year (UNAIDS, December 2001; available online.

Much of the increase was in the region’s giants, India and China, where new data also document HIV’s spread from severely affected high-risk groups (injecting drug users, sex workers and migrant laborers)—some with prevalence rates over 50%—into the general population (see also MAP report; available online).

Overall prevalence is still relatively low in Asia, where more than 60% of the world’s population live. But speaker after speaker at the International Congress on AIDS in the Asia-Pacific (ICAAP, Melbourne, 5-9 October 2001) and India’s International Conference on HIV/AIDS (16-19 December, Mumbai) projected that these early-stage epidemics will burgeon into tens of millions of new infections within the decade, leading Asia to eclipse sub-Saharan Africa as the region with the world’s highest number of HIV-infected people.

Adding to the grim picture was the backdrop of the two meetings: the US bombing of Afghanistan began during ICAAP, which took place four weeks after the World Trade Center attack, while the Mumbai conference began within days of the Indian Parliament bombing and the resulting escalation of tensions with neighboring Pakistan. Corridor conversation focused largely on discussions of how these events have changed the global landscape and affected government priorities for attention and resources, just as many countries face ballooning numbers of sick and dying people, and of affected families and communities.

Alongside the dire predictions was a recognition that strong preventive measures implemented quickly could go a long way towards blunting the coming wave of infections, while vaccines are key in the longer term. But many countries in the region have not mounted comprehensive prevention programs, and few have prioritized AIDS vaccine development. There are exceptions: decreasing prevalence among pregnant women in Cambodia suggests that efforts to stem HIV spread are starting to pay off, while Australia and the Philippines show continued success in keeping infection rates low. China and India have both launched HIV vaccine projects, and a major initiative is underway in Australia (see article).

But for the biggest success stories on these fronts, eyes at both meetings turned to Thailand. National prevalence rates (now just over 2%) have dropped by 80% over the past decade, and it is estimated that the country’s early response—which combined intensive epidemiological surveillance, high-level political commitment, pragmatic efforts to curb the demand for commercial sex, and harm-reduction approaches such as the "100% condom program"—prevented between 1 and 2 million infections.

"Thailand’s success shows that we’re not helpless against HIV," says Tim Mastro, head of the US Centers for Disease Control (CDC) HIV vaccine unit in Atlanta, and formerly of the CDC’s Bangkok unit. "We really can do something to stop this virus."

Thailand’s vaccine agenda

From early on, microbicides and vaccines were seen as key, albeit future, weapons in the country’s response to HIV/AIDS. By 1992, Thailand—with its extensive field experience in testing other vaccines—began engaging in vaccine issues, with crucial support from the World Health Organization’s Global Programme on AIDS, then headed by Jonathan Mann.

In the current issue of the IAVI Report we highlight Thailand’s current AIDS vaccine activities, drawing on discussions with the principals in Bangkok as well as presentations at ICAAP, Mumbai, the "AIDS Vaccines 2001" conference in Philadelphia (see article) and Thailand’s International Conference on HIV Vaccines (Bangkok, 23-27 July 2001). (Additional coverage of the Mumbai meeting will be included in the next issue.)

At present these activities are centered on the ongoing Phase III trial of VaxGen’s gp120-based vaccine (see article)—one of only two AIDS vaccine efficacy trials worldwide—and the prime-boost efficacy study planned for late 2002 (see article) which will be a large, community-based trial in Thailand’s south (see article and interview with Supachai Rerks Ngarm). Both come after nearly a decade of planning, building capacity and carrying out smaller studies: Of the 13 Phase I and II HIV vaccine trials in developing countries to date, 7 were done in Thailand. Down the road, a new Australian prime-boost strategy based on Thai subtype E strains should undergo Phase I testing in 2004, while a Japanese-Thai collaboration is developing HIV vaccines based on the bacterial vector BCG.

But some Thai researchers are wary that the "success story" label can breed complacency towards today’s challenges. Thailand has nearly one million people living with HIV/AIDS, and providing care—let alone making anti-retrovirals widely available—is a formidable task now facing the public health system. Another is curbing the still-rampant epidemic in IDUs, where HIV prevalence has barely changed over the past decade even as it dropped in virtually all sexual risk groups. While Thailand is almost alone within Southeast Asia in offering methadone treatment for heroin withdrawal, it has yet to move towards other harm-reduction measures, such as wide-scale needle exchange programs or long-term methadone maintenance, that could have a real impact. In a region which is flooded with plentiful, cheap heroin, reducing HIV spread in IDUs is crucial not just for Thailand’s epidemic but for that in neighboring China, Vietnam, India and Myanmar.

There is also concern over a possible resurgence in new infections, given the low rates of condom use by steady couples and the fact that young men increasingly seek partners among peers rather than commercial sex workers; vaccine preparedness studies in southern Thailand recently found that young married women now represent one of the highest-risk groups (see article). On the political front, Thailand is still operating without an AIDS vaccine subcommittee, which was dissolved last summer amid renewed disputes over Phase III trials of the Remune therapeutic vaccine (see IAVI Report Dec. 2000-Jan. 2001), temporarily shutting down a key component of the approvals pathway for clinical studies just as the next Phase III trial is being prepared.

In the longer term, Thailand’s role in HIV vaccine testing is also changing. With heterosexual transmission rates dropping to a level that makes future efficacy studies difficult in this population, the country may focus on higher-risk groups and early-stage trials. In a "Viewpoint" article (see article), Bangkok-based vaccine developer Jean-Louis Excler advocates building Phase III testing capacity in neighboring countries that are now experiencing more severe heterosexual epidemics. While acknowledging the difficulties of working in places with far less infrastructure and political commitment than Thailand’s, he argues that closer collaboration between international players and among local stakeholders are essential missing ingredients.

Within Thailand, another worry is the sparsity of new candidate vaccines based on subtype E, the region’s predominant subtype (but actually a recombinant between subtype A and a never-detected "pure" subtype E)—not to mention its emerging recombinants. With the epicenter of the epidemic now in sub-Saharan Africa, most international attention is focused on subtypes C and A. But Mahidol University’s Punnee Pitisuttithum, a key figure in Thailand’s vaccine effort, echoed sentiments expressed by several others when she concluded a long discussion of the country’s vaccine work with the plea, "Don’t forget Thailand!"