TOKYO: Japan's requirement of domestic clinical trials for COVID-19 vaccines cost it precious time in inoculating its population, vaccine programme chief Taro Kono said on Tuesday (Jun 15).

About 4.8 per cent of Japan's population has been fully vaccinated, a Reuters tracker shows, the lowest rate among large, wealthy economies at a time when tens of thousands of visitors are poised to arrive for the Tokyo Olympics starting on Jul 23.