GENEVA: The head of the World Health Organization hailed the rapid progress towards a Covid-19 vaccine but insisted Friday that every country must reap the benefits.

"A vaccine will be a vital tool for controlling the pandemic, and we're encouraged by the preliminary results of clinical trials released this week," Tedros Adhanom Ghebreyesus said, in closing the WHO's annual assembly.

US pharmaceutical giant Pfizer and its German partner BioNTech announced Monday that their candidate vaccine had proven 90 percent effective in ongoing final phase trials involving more than 40,000 people, less than a year after the novel coronavirus emerged in China.

"Never in history has vaccine research progressed so quickly. We must apply the same urgency and innovation to ensuring that all countries benefit from this scientific achievement," said Tedros.