HIV vaccine trial results are an important step forward in developing an effective vaccine, say WHO and UNAIDS
WHO/UNAIDS HIV vaccine initiative calls for accelerated research to build on trial accomplishments
Geneva, 24 February 2003 - Preliminary results of a large-scale trial of a candidate AIDS vaccine announced today by the US-based biotechnology company VaxGen suggest that it is possible to protect some individuals from HIV infection. The trial of the company’s AIDSVAX vaccine appears to show a protective effect among non-Caucasian populations, especially African Americans, although sample sizes were small. However, for the majority of the participants, who were Caucasians, the effect of the vaccine was minimal.
The company stressed, however, that the results announced today only represent findings from an initial analysis. Additional studies will be conducted over the coming weeks to further clarify the data. “These result are promising. The trial provides clear evidence that a vaccine can work,” said Dr Peter Piot, Executive Director of UNAIDS. “However, there is an urgent need for more targeted research to find out why the candidate vaccine only seems to work in certain population sub-groups. In the meantime, we must continue to expand existing prevention efforts, which have proved their effectiveness when they are implemented at full scale.”
This trial vaccine is a promising first step, but an effective vaccine providing widespread protection is still not on the horizon. The AIDSVAX Phase III trial was the first large-scale human trial of an HIV vaccine. The trial was made possible because of the involvement of over 5400 volunteers from the United States, Canada, and the Netherlands, the majority of whom were men who have sex with men.
Phase III trials, which involve thousands of volunteers, focus on whether a candidate vaccine is effective and can safely protect people. These are only conducted once Phase I and II trials have ensured that the vaccine is safe and produces an immune response against the virus.
The vaccine used in this trial was designed to reduce susceptibility to infection with HIV subtype B, which is prevalent in the Americas, Western Europe, Australia, and New Zealand. To date, eleven subtypes of HIV-1 have been identified. One of the major challenges in HIV vaccine development is to develop one or multiple vaccines effective against all major subtypes of HIV.
“Continued HIV vaccine research remains an urgent global need,” said Dr Gro Harlem Brundtland, Director-General of WHO. “We will need many more trials to develop effective HIV vaccines, particularly against the most prevalent HIV sub-types, which are having a devastating impact on populations in sub-Saharan Africa.” Dr Brundtland added that national governments, the private sector and the international community must ensure that a robust programme of vaccine research is continued and that effective prevention, care and treatment programmes are available.
VaxGen is also conducting another Phase III trial in Thailand, involving a vaccine candidate based on HIV subtypes B and E. That trial, which involves more than 2500 volunteers, mostly injecting drug users, is expected to provide additional valuable information about the potential efficacy of this type of candidate vaccine. Results are expected by late 2003. VaxGen is also currently conducting pre-clinical research to develop a vaccine against the most common subtype, subtype C, which accounts for approximately 50% of all new HIV infections worldwide.
Several other candidate vaccines based on different HIV subtypes are being tested by other public and private organizations, mostly in the United States and Europe, but also increasingly in developing countries, where a total of 22 vaccine candidates have been or are being tested including in Brazil, Haiti, Kenya, Peru, Thailand, Trinidad and Tobago, and Uganda. At least one of these candidate vaccines is expected to enter Phase III trials this year in Thailand, with results available four years later.
The WHO/UNAIDS HIV Vaccine Initiative was established in 2000 to facilitate the development and evaluation of appropriate HIV vaccines, ensuring that once they are developed they are affordable and available to all people in need.
According to UNAIDS and WHO, an estimated 42 million people are living with HIV/AIDS worldwide, of which close to 30 million live in sub-Saharan Africa. An estimated 5 million people were newly infected with the HIV virus in 2002.