The Global Alliance for Vaccines and Immunization (GAVI) said on Monday it had signed two advance purchase deals with Chinese drugmakers Sinopharm and Sinovac to provide up to 550 million COVID-19 vaccines to the COVAX program.

The new agreements include up to 170 million doses of the Sinopharm shot and up to 380 million shots of the Sinovac vaccine, through to the middle of 2022, the statement said. Sinovac confirmed the agreement in a statement.

“The agreements, which come at a time when the Delta variant is posing a rising risk to health systems, will begin to make 110 million doses immediately available to participants of the COVAX Facility, with options for additional doses,” GAVI said.

GAVI, which runs the global vaccine sharing scheme COVAX with the World Health Organization (WHO) did not immediately provide details of which countries would receive the doses.

Deliveries can start quickly because both vaccines have already been granted emergency use listing by the WHO, GAVI Chief Executive Officer Seth Berkley said.

COVAX, which distributes vaccines to poorer countries, has battled to meet its early commitments amid Indian export disruptions, forcing many countries to freeze their vaccination programmes in their early phases.

However, its latest supply forecast shows that the programme is on track to deliver more than 2 billion doses by early 2022. The vaccines by Sinovac and Sinopharm join nine other vaccines and vaccine candidates already in the programme including those by AstraZeneca and Moderna.