Dec 10 (Reuters) - Moderna (MRNA.O) said on Friday it would supply up to 150 million extra doses of its COVID-19 vaccine to the Gavi vaccine alliance for distribution through the COVAX vaccine-sharing facility in 2022. Of those 150 million doses, 20 million are fixed via a supply agreement for the second quarter and the other 130 million are options for mid-2022. Moderna also said it would speed up supply of 20 million doses to COVAX to make 54 million doses available to the vaccine-sharing scheme by the end of the year. The COVAX initiative is co-led by Gavi, the World Health Organization (WHO) and the Coalition for Epidemic Preparedness Innovations (CEPI). It has so far delivered more than 600 million doses to 144 countries which is just a fraction of the 8 billion distributed across the world, with the bulk concentrated in wealthier countries. After a slow start due to supply setbacks, the roll-out that seeks to address this inequity is accelerating thanks in part to the resumption of Indian exports after a more than six-month gap. read more Moderna"s announcement came after a call from the CEO of the Gavi alliance for more predictability about supplies from manufacturers. "We need companies to be transparent about this so that countries can plan for large-scale delivery at the national level," Gavi alliance CEO Seth Berkley said. Aurelia Nguyen, managing director at the COVAX facility, welcomed the agreement with Moderna on Friday and repeated a call for manufacturers to prioritise "transparent, consistent and predictable supply to COVAX." Other suppliers to the programme include AstraZeneca (AZN.L), Sinopharm and Johnson & Johnson (JNJ.N) Reporting by Amruta Khandekar in Bangalore and Emma Farge in Geneva; Additional reporting by Stephanie Nebehay; Editing by Amy Caren Daniel, Maju Samuel and Jane Merriman Our Standards: The Thomson Reuters Trust Principles.