China"s SciClone Pharmaceuticals (6600.HK) has begun a clinical trial to test if its hepatitis B treatment Zadaxin helps to boost immunity provided by COVID-19 vaccines, it said on Monday. SciClone said it is using an inactivated COVID-19 vaccine in its trial but did not specify which one. Three coronavirus vaccines approved in China use inactivated virus and have been developed by China National Pharmaceutical Group (Sinopharm) and Sinovac Biotech (SVA.O). "In view of the mechanism of action of Thymalfasin (Zadaxin) and previous clinical studies, the combination with Thymalfasin may help increase the level of SAR-Cov-2 neutralizing antibody and prolong the antibody protection time," it said in a statement. The company plans to recruit 200 trial participants across China and evaluate the safety and ability to elicit immune responses from the vaccine when combined with Zadaxin. It said the drug has been approved as a vaccine enhancer for the treatment of patients with chronic hepatitis B and immune impairment.