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The need for vaccine research
Vaccines are preparations which direct the immune system to prevent or control infection by an infective agent or pathogen. 'Preventive vaccines' would be given to people who are uninfected with HIV, to prevent or limit HIV disease - or at the very least, prevent onward transmission - if they are subsequently exposed to HIV. Vaccines are also being developed as therapies for people who are already living with HIV. Such 'therapeutic vaccines' or 'immunogens' are covered in HIV therapeutic vaccines in Anti-HIV therapy: Restoring the immune system.
Despite more than 20 years of AIDS research, there is still no preventive vaccine which has been shown to be effective in humans. Nonetheless, a great deal of scientific progress has been made and much more can be expected. Translating that understanding into products which can change the course of the epidemic remains a major challenge for reasons which go beyond scientific uncertainty, with political, economic and social dimensions.
The need for vaccine research
At an individual level, antiviral drugs prolong life and reduce the need for hospital care to an extent that can easily justify their cost. However, in terms of global public health, their impact may be limited. There is not yet any strong evidence that they reduce transmission, other than from mothers to babies. Drug resistant viruses rapidly appear and can be transmitted to uninfected people. The drugs require complex monitoring, education and support - to prevent or deal with viral drug resistance and to cope with side effects - which is a challenge to healthcare systems.
Current prevention technologies, including treatment of sexually transmitted diseases and targeted promotion of condoms, can make a big difference to HIV epidemics at certain stages of their development and in some sections of society. These interventions could be enhanced with the development of effective and non-toxic microbicides - such as gels or creams to inactivate HIV in semen. Sustaining their use in the longer term remains a major challenge.
Other behavioural changes, including postponement of sex among young people and avoidance of multiple simultaneous relationships, have had a major impact on HIV transmission in some countries. Unfortunately, these are generally countries where great many sexually active adults are already HIV-positive.
The best long-term prospect of eradicating the virus as a public health problem therefore remains the development of effective preventive vaccines, however difficult or long-term the process may be.
Progress to date
The mechanism by which HIV infects human cells is now better understood than for most viruses. This has re-opened the possibility of making broadly protective antibody-inducing vaccines by targeting the virus at particular stages during the process of cell entry when it is most vulnerable.
In recent years, researchers have focussed on generating cellular immune responses to prevent HIV infection. Several research groups are now combining various approaches to induce both antibody and cellular (killer T-cell) immune responses.
Investment and research
Vaccines attract far less investment than treatments, but the level of interest and political commitment has markedly increased in recent years.
The World Health Organization’s Global Programme on AIDS and its inter-agency successor, the United Nations Joint Programme on AIDS (UNAIDS) have consistently advocated vaccine development and have supported a number of countries in developing national plans.
The International AIDS Vaccine Initiative (IAVI), a non-governmental organisation founded in 1996, has as its goal "to ensure the development of safe, effective, accessible, preventive HIV vaccines for use throughout the world." IAVI has raised substantial funding from governments and private foundations, including the Bill and Melinda Gates Foundation, and played a key role in bringing together public and industrial researchers from around the world.
On May 18th 1997, United States President Bill Clinton announced that finding an HIV vaccine within ten years was a national goal, and funding for HIV vaccine research was steadily increased through his administration and that of President George W. Bush. The need for an HIV vaccine has been endorsed internationally by successive G8 summits and the United Nations General Assembly in its special session on HIV/AIDS.
The United States is funding an international HIV Vaccine Trials Network, which is promoting a major programme of international clinical trials with a series of industry partnerships, notably with Merck & Co., the pharmaceutical company which has by far the most substantial private sector HIV vaccine research and development programme.
The latest development in the field is the Global HIV Vaccine Enterprise, defined as a virtual consortium of independent agencies, working to a shared strategic framework. The aim is to coordinate work more effectively than in the past, with a secretariat initially been provided by the Bill and Melinda Gates Foundation. An early contribution to the programme is a call for proposals from the United States National Institutes of Health to set up a new vaccine and immunology research institute, probably in an American university, to address basic scientific issues. Other priorities include investment in clinical trial sites and standardisation among laboratories of new immunological methods used to assess responses to HIV vaccines.
Whether the necessary financial, political and social conditions can be created to enable such a vaccine to be used to maximum effect is another question.