The HIV vaccine trial launched in February has been suspended after it was discovered that it failed to prevent infections.
The trial was brought to a halt on Friday after interim results from sister trials in the US and Australia showed it failed to prevent HIV infection. But researchers of the Phambili trial claim the decision is just a safety precaution.
"We know it's safe and that it will not cause HIV, but we do not know if it will protect against HIV infection," said Glenda Gray, chief investigator in the South African trial of the Merck MRKAd5 vaccine at Chris Hani-Baragwanath Hospital.
"We all feel despondent about the sudden halt of the vaccine's trial. We will take a month to examine the data from the sister trial before deciding whether to continue with the Phambili trial in a modified form or suspend it," Gray said.
Seven hundred people had enrolled in the Phambili trial at five sites across the country. The organisers have assured volunteers that they are not at risk.