Better ways to combat HIV than seeking a vaccine
As HIV experts gathered for a major global conference in Boston, US, earlier in March, it was a reminder of a decade ago when respected Harvard professor Ronald Desrosiers gave a plenary talk at the same conference, in same venue. This was soon after the STEP vaccine trial, which, instead of protecting people from HIV, was found to have increased their infection risk 41%.
This was a dark moment for the HIV-research community as many had high hopes the STEP vaccine would work. Yet I fear lessons have not been learnt from past mistakes.
Desrosiers stressed that the failure should have not come as a surprise, given that clinical trials carried out in monkeys had not shown convincing protection from infection. He criticised the use of large amounts of money "to manufacture and test products with little reasonable hope of efficacy". Nearly $200m had been spent on the STEP clinical trial, and even more on product development.
However, the failure of the STEP vaccine trial did not dissuade researchers from continuing to hunt for a vaccine.
A decade and billions of dollars later, Desrosiers’s criticism still looms large: "Are human-vaccine trials the best use of resources?"
In Africa, the question is particularly acute in the face of declining resources. UNAids reported a 7% decline in donor funding for the fight against HIV in poor and middle-income countries between 2015 and 2016. This is the lowest funding level since 2010.
A lot of progress has been made in HIV-prevention strategies as well as in understanding the virus. Since 2000, the global response to HIV has averted 30-million new infections and nearly 8-million AIDS-related deaths, according to UNAids.
However, on the vaccine front, one essential piece of the puzzle is still missing. It is still not known how to prompt people’s immune systems to create their own antibodies which can protect against HIV — known to scientists as "broadly neutralising activity" – using a vaccine.
Conventional vaccines activate the body’s immune system to recognise and destroy disease-causing agents such as viruses and bacteria. But because HIV changes rapidly, an ideal vaccine would need to cause the recipient to create antibodies that are effective despite those many changes, or "broadly neutralising". As scientists continue to grapple with this challenge, several HIV vaccine clinical trials are under way.
One vaccine prototype being tested will use a broadly neutralising antibody made in a laboratory. But while the prototype has worked in tests on monkeys, it may still not be practical. The vaccine is expensive, works only for a few weeks or months and doesn’t appear to be effective against the strain of HIV prevalent in Southern Africa. It does not take a medical expert to figure out that the chances of broad success are slim. Yet, expensive clinical trials are under way for this prototype in North America, South America, Europe and Africa.
Instead of ploughing more of our limited resources into large-scale vaccine clinical trials, the global community should provide more support to proven strategies for HIV prevention — such as pre-exposure prophylaxis, or PrEP, where individuals at high risk of contracting HIV take antiretrovirals (ARTs) to prevent infection.
While there is valid concern about the possible side effects of long-term ARV use as PrEP, the drugs are getting better and there are now long-term formulas that can be administered just once every month or two. This significantly reduces the discomfort associated with taking daily doses of the drugs while making it easier for programmes to administer.
In SA about 50% of HIV-infected people who could benefit from ARVs are not accessing them due to a lack funds — leading to more than 100,000 unnecessary deaths for the untreated. The same is true in many East African and Southern African countries — the region worst affected by the HIV epidemic — where nearly half the infected people do not have access to treatment.
An HIV-positive person being treated with ARVs is less likely to pass on the virus, making ARVs a critical tool in preventing the spread of the virus. This is not to say that all HIV-vaccine research should stop — an effective vaccine would undoubtedly be the most effective weapon against HIV.
History also teaches that in drug and vaccine development, failures must be experienced before success. However, research must be appropriately targeted to solutions that are the most likely to work and are easily widely applicable.
Based on the current reality, HIV treatment and prevention strategies that have been proven to work would be a much better use of the millions of dollars being spent on the large-scale vaccine clinical trials. It may not make vaccine researchers happy, but it would save lives.
• Chopera is the executive manager for the Sub-Saharan African Network for TB/HIV Research Excellence.