Last updated: September 24, 2009 7:07 pm

Scientists hail HIV vaccine breakthrough

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A patient with Aids sits on his bed at a hospital©AFP

The findings of a scientific trial offer hope that Aids could be preventable. Above, a patient with the condition sits on his bed at a hospital in a Buddhist temple in Thailand

Scientists on Thursday heralded the results of the world’s first successful trial in humans of an HIV vaccine, which cut the risk of infection by 31 per cent.

The positive results in a test of more than 16,000 Thai volunteers offered a boost to researchers who have spent more than 20 years and more than $8bn (€5.4bn, £5bn) on studies with little sign of progress. It could help revitalise lagging donor funding and interest by companies in the field. Colonel Jerome Kim, HIV vaccines product manager for the US army, which provided funding for the trial, said: “This is the first evidence that a safe and effective HIV vaccine is possible.”

However, he and other specialists warned that the findings were of only “modest” advances and raised many technical and practical questions – so that it would be several years, even at the most optimistic, before a vaccine could be approved by regulators.

Anthony Fauci, director of the ,US National Institute of Allergy and Infectious Diseases the main sponsor of the $105m project, called RV 144, said: “This is the beginning of the effort. It has opened up the door for us to ask fundamental scientific and clinical questions.”

The trial used a combination of ALVAC HIV – from Sanofi-Aventis, the French pharmaceutical company – as “prime” vaccine, with a second vaccine booster called AIDSVAX B/E, developed by GenVax of the US, and since ceded to the non-profit group Global Solutions for Infectious Diseases. It was overseen by the Thai authorities, with US military support. The work, beginning in 2003, was complex, involving initial interviews of 60,000 people aged 18-30 from the Rayong and Chon Buri provinces, before 16,402 initially took part. Almost 0.8 per cent contracted HIV, including 51 people who were vaccinated and 74 who were not.

Thailand was chosen because its high rate of HIV infection helped to minimise the total number of recruits required, as well as its well developed medical infrastructure and strong commitment to the issue.

However, the government’s subsequent success with HIV prevention programmes, combined with ethical rules requiring the highest “standard of care” – including counselling and distribution of condoms – meant the numbers recruited were not large enough for US regulatory approval.

The efficacy of 31 per cent would in any case be insufficient to justify use of the vaccine, although based on the latest trial, and previous studies in several thousand patients, there are no signs to date that either of the two vaccines creates any serious side-effects or concerns over safety.

There is also a practical issue: with six separate vaccinations of a complex product required over six months in RV 144, the costs and difficulties of widespread adoption would be enormous. Condoms, circumcision and counselling will remain far cheaper and more effective options for a long time to come. And some fear that this week’s findings may displace scarce money from such practical tools to scientific hopes for the future.

The findings leave many questions unanswered. Most important is that while those who were vaccinated had a lower rate of HIV infections, it had no effect in reducing the “viral load” or presence of HIV for those who had been vaccinated. This reinforces uncertainty over the mechanism by which vaccines affect the human immune system.

There are uncertainties about the longer term probability of infection and the development of HIV in those who have been vaccinated; and the effects in other groups at higher risk of HIV including sex workers, gay men and intravenous drug users.

Scientists also need to consider how best to improve efficacy towards more significant levels, and how far the vaccine would provide protection against the different types of the HIV virus that circulate in Africa and in other parts of the world.

Additional reporting by Tim Johnston

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