A sixth experimental COVID-19 vaccine from China is now being tested in humans after Clover Biopharmaceuticals said on Friday an early-stage study of its candidate was underway with vaccine boosters from UK's GSK and US based Dynavax. The trial, which is enrolling about 150 adult and elderly patients, will evaluate the two different boosters, or adjuvants, in combination with Clover's candidate shot, SCB-2019, the Chinese company said. There are no approved vaccines or treatments for the illness caused by the new coronavirus, but about a dozen vaccines are being trialled globally as drugmakers and governments scramble to combat the health crisis. Clover said initial safety data from the study was expected in August this year, and it would target to start broader studies by the end of this year. China now accounts for almost half of the clinical trials testing COVID-19 vaccines, including candidates from CanSino Biological, and Sinopharm and the Wuhan Institute of Biological Products. GSK, the world's largest vaccine maker, on Friday underscored its commitment to backing a conventional immunisation approach. It has mainly acted as a contributor of adjuvants, or efficacy boosters, that are combined with proteins called antigens that help build immunity. Clover and the British drugmaker began their collaboration for a coronavirus vaccine in February this year and the Chinese firm partnered with Dynavax the following month.