US drug developer Novavax Inc has said it has started a mid-stage study of its experimental Covid-19 vaccine in South Africa, as the country experiences a surge in coronavirus cases, Reuters reported.

“Because South Africa is experiencing a winter surge of Covid-19 disease, this important Phase 2b clinical trial has the potential to provide an early indication of efficacy,” Novavax research chief Gregory Glenn said.

The trial of Novavax's NVX-CoV2373, backed by a $15 million grant from Bill & Melinda Gates Foundation, was being conducted in two separate groups, one comprising 2,665 healthy volunteers and the other, 240 HIV-positive adults.