Estimates for HIV vaccine demand `sketchy` says IAVI

Although more than 30 potential HIV vaccines are currently being tested in 19 different countries, information about global demand and uptake by high risk groups is inadequate, according to a paper published in the October issue of PloS Medicine.

“For a vaccine to make a difference in halting the AIDS pandemic, it needs to be widely available and accessible, and must be taken up,” say Robert Hecht and Chutima Suraratdecha, in Estimating a demand for a preventive HIV vaccine: why we need to do better.

Some potential vaccines have reached the human testing stage with a large phase III trial currently being carried out in Thailand. Another trial (phase IIB) which is investigating whether a vaccine built on an adenovirus vector platform will work, is being carried out on several thousand volunteers in Latin America, the Caribbean, Europe, and North America.

In the paper, which reports on 18 previous studies into HIV vaccine demand in countries with significant HIV epidemics, the authors point out that the first generation HIV vaccines are likely to be very expensive and not very effective, lowering the chances of widespread use. “Furthermore, the stigma associated

with HIV/AIDS, if not adequately addressed, may lower demand for a vaccine.”

For these reasons, governments and health policy makers need to be thinking about who should be targeted and how to ensure that the people who will benefit most from vaccination are reached. “If combined effectively with parallel policy analysis on vaccine impact, cost-effectiveness, and strategies for financing and delivering an HIV vaccine, such additional work on vaccine demand could make an important contribution to speeding up development and access to a vaccine that could help to stop the epidemic and end AIDS,” say the authors.

Globally, demand is projected to be between 200 and 300 million doses per year, especially in the early “catch-up years” of vaccination, with one author estimating as many as 700 million doses needed.

Four studies - in Brazil, India, Southern Africa and Thailand - have looked at what the needs at country level will be once a vaccine becomes available. If the general population is targeted, it was estimated that in Brazil over 121 million doses would be needed while another 195 million doses would be needed in Southern India.

However, narrower targeting, giving the vaccines to high risk groups, would lower the number of required doses dramatically — down to 9.1 million doses in Brazil and 9.6 million doses in Southern India. The African study estimated that 1.3 million doses would be needed to protect 15-year-old school students in Southern Africa, while the Thai study considered that 5.9 million doses would cover the people in ‘priority groups’ while an extra 1.3 million doses would be needed annually to maintain that coverage.

While targeting high-risk groups seems the more realistic strategy, the authors say the research done so far has not yielded much information about demand for and uptake of vaccines in the groups most likely to benefit from them, such as commercial sex workers and intravenous drug users. “Little is known about the uptake of vaccines and other health services by adults and marginalized social groups in developing countries.”

The studies estimating doses needed also made assumptions about cost (that it will be relatively low) and efficacy (that it will be one hundred percent effective), both of which are unlikely to be borne out by reality. Those studies that have looked at cost, and whether it will be a barrier have found that, indeed, when cost goes up, interest in vaccine uptake goes down. However, if a vaccine is known to be effective, respondents said they were more willing to pay a higher price.