Scientists need to resolve how an HIV vaccine can be tested on children before the vaccine is ready for widespread human use, according to Professor Helen Rees, head of the Medicine Control Council (MCC).
The MCC has to give permission for drug and vaccine trials in this county.
“The primary target population for an HIV vaccine is children under the age of 14 [before they become sexually active],” said Rees.
“But human trials are usually conducted on adults, who are biologically and physiologically different from children,” said Professor Rees.
“If we wait to complete an adult trial, that will take five years. But if the vaccine has not been tested in children, there will be no safety data for children and it would be very difficult for the MCC to license the vaccine for use in children. But how do you start testing on children and babies?”
One option could be to start tests on high-risk groups – such as babies born to HIV positive mothers who were being breastfed, said Professor Rees.
While the scientists hope to begin human trials in the third quarter of this year, Professor Rees said that “we don’t want the regulatory process to be a barrier, but no one can prejudge the regulatory process”.
Give the caution with which the MCC has approached the licensing of Nevirapine for mother-to-child-transmission, it is quite possible that human trials may only begin next year.
Before approval is given for any human trials, the MCC has to review all science, protocols and ethics relating to the proposed trials.
The MCC, Medical Research Council and SA AIDS Vaccine Initiative (SAAVI) have also set up a reference group to review vaccine trial applications.
South Africa is one of a number of countries which has recently begun to grapple with problems associated with a vaccine, said Professor Rees.
The World Health Organisation (WHO) recently convened a meeting for scientists and regulatory authorities from a range of countries, including the USA, Britain, Uganda, Thailand and Kenya, to discuss how best to run vaccine trials.
The intention of the meeting was to review both the scientific knowledge relating to vaccines and the standards involved in evaluating a vaccine.
“We need to define what an effective vaccine is,” said Professor Rees. “Is it one that offers complete protection from HIV? Or do we accept a vaccine that allows some infection, but where the virus is not as aggressive? Do we accept a vaccine that is able to greatly reduce the viral load? And what is the effect of vaccinating people who are already HIV positive?”
Rees said participants at the WHO meeting were also concerned that international standards for measuring a vaccine’s efficacy needed to be set.
“Will the laboratories in different countries be able to maintain the same standards? And if we are measuring immune response, we need to ensure that there is an international standard. But what is a normal immune response?”
Participants also debated whether a person who became HIV positive as a result of being tested with the vaccine should be entitled to anti-retroviral drugs. It would also be difficult to know whether such a person became infected from the vaccine trial or from infection from another person.
Professor Rees added that, as many of the regulatory authorities in the developing world were weak, the WHO and the Joint United Nations Agency on AIDS (UNAIDS) were considering setting up a regulatory reference group to assist them to deal with these “complex problems”.