HIV vaccine results encouraging but current preventive measures vital – UN

24 September 2009

The largest ever HIV vaccine clinical trial to date provides hope for eventual immunization in the general population, but much more work needs to be done and current preventive strategies must be maintained, United Nations health agencies cautioned today


“The study results, representing a significant scientific advance, are the first demonstration that a vaccine can prevent HIV infection in a general adult population and are of great importance,” the World Health Organization (WHO) and the Joint UN Programme on HIV/AIDS (UNAIDS) said in a statement, calling the results of the trial encouraging.

The RV144 HIV vaccine study in Thailand showed a 31.2 per cent efficacy in preventing HIV infections, a modestly protective result with no safety issues noted. “However, these results have instilled new hope in the HIV vaccine research field and promise that a safe and highly effective HIV vaccine may become available for populations throughout the world who are most in need of such a vaccine,” the agencies said.

“Until a highly effective HIV vaccine becomes available, UNAIDS and WHO underline the importance of effective and proven HIV prevention methods for all people,” they added, citing changes in behavioural and social norms, correct and consistent condom use, access to safe injection equipment, and male circumcision to combat the infection, which is spread by sexual contact and use of contaminated needles.

They warned that much more has to be done to analyse the data, understand the protective mechanism, determine the duration of protection, and map next steps.

“It remains to be seen if the two specific vaccine components in this particular regimen would be applicable to other parts of the world with diverse host genetic backgrounds and different HIV subtypes driving different regional sub-epidemics,” they said, stressing that once a vaccine becomes available, it will need to be universally accessible to all persons at risk.

Moreover, early HIV vaccines with modest levels of efficacy would most likely have to be used as complementary tools in combination with the current strategies.

The trial, involving 16,395 Thai adult male and female volunteers, was a test-of-concept of a novel regimen with two different candidate vaccines, carried out by the Thai Ministry of Public Health and sponsored by the United States Army Surgeon General with funding from the US National Institute for Allergy and Infectious Diseases and the US Army Medical Research and Materiel Command.

The two agencies began supportive work for the trial in 1991, when Thailand was recommended as one of the WHO-sponsored countries in preparation for HIV vaccine trials.

“WHO and UNAIDS will work with the global HIV stakeholder community to further understand and resolve a range of questions related to the potential introduction of an HIV vaccine of moderate protective efficacy. This includes additional, in-depth trials in different populations with diverse host and virus genetic backgrounds,” they concluded.

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