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The need for a vaccine
Historically, vaccination is the only strategy that has ever led to the elimination of a viral disease, namely smallpox, in poor countries as well as in wealthy ones, for women and children as well as for adult men. While the biology of HIV is less favourable than smallpox to vaccine development, some experimental vaccines do, to varying degrees, protect animals against related viruses.
An ideal vaccine would be cheap to produce, stable at room temperature, easy to transport and administer without special equipment, completely safe, and would need only one dose to provide complete lifelong protection against all routes of transmission and all variants of HIV. All current vaccine candidates are likely to fall short of these criteria, although even an imperfect vaccine could deliver public health benefits and provide further insights for prevention and treatment strategies.
While no-one knows when a vaccine will become available, and while other responses are sometimes very effective, nothing else would seem to offer a globally sustainable answer to HIV and AIDS. Reductions in HIV prevalence have been achieved through behaviour change in many communities, but mostly when HIV is present at high levels and with no sign that this can eradicate the virus. There is no reason to believe this effort can be maintained, and some evidence that it is not, once HIV is seen as a declining problem. HIV can develop resistance to all known antiviral treatments and multi-drug-resistant HIV can be transmitted from person to person.
There are people in all communities who lack the control over their circumstances to ensure their protection from HIV and AIDS. While microbicides may usefully extend prevention options and serve as valuable prototypes for vaccine development, it is not clear that these can be delivered sustainably to everyone at risk. (Conversely, an AIDS vaccine will not diminish the case for developing microbicides that can protect against a broader range of sexually transmitted infections.)
So, however long it takes, only an effective preventive vaccine has any reasonable prospect of eliminating HIV as a global public health problem. To achieve this, we need to think in terms of a series of vaccines to be developed and tested, in parallel and then against each other, possibly in combinations, and successively improved over many years. This process will require extended collaborations between countries with the technical resources to develop the vaccines and those with the largest populations affected by HIV. It will require private sector expertise in manufacturing and production of vaccines, underpinned by public financial and legal guarantees where market mechanisms fail to secure the investment to take products forwards. It will need community education and mobilisation to enable evaluation to proceed in an ethically acceptable way, with backing from governments and international institutions.
For the communities worst affected by HIV and AIDS, whose members must be involved in any programme to evaluate preventive vaccines, there are increasingly complex medical and social issues to be addressed. At a community level, any vaccine will need to be evaluated and used in combination with other treatment and prevention strategies. It is essential that this happens in ways that reinforce those other strategies and do not undermine them.