The COVID-19 vaccine developed by China's Sinopharm has been approved by the World Health Organization (WHO) for "emergency use."

This means its safety, efficacy and quality has been checked and it can be used by the international COVAX vaccine effort.

WHO Director-General Tedros Adhanom Ghebreyesus said in a news conference that "vaccines remain a vital tool" in the fight against the pandemic but the "volume and distribution of vaccines remains insufficient."

He said by adding the Sinopharm jab to COVAX's arsenal, the relief program could now draw on six approved vaccines to help fight the virus in the world's poorest nations.

Sinopharm Biotech's chairman, Yang Xiaoming, has promised to increase production to meet demand. In an interview with CGTN he explained that plans to produce 3 billion doses are in the final phase and have involved building new factories and agreeing deals with other countries to produce packaging.

More than 100 countries have already agreed contracts with the company to supply vaccines.

WATCH: Sinopharm Biotech chairman talks to CGTN about vaccine production plans

Ghebreyesus said the Sinopharm shot has also been given approval by the Strategic Advisory Group of Experts on Immunization (SAGE), which cleared it for use in those "18 years and older in a two-dose schedule."

Many governments around the world wait for the the WHO's emergency use certificate to be granted before using a new medicine, so the announcement is likely to accelerate the global roll out of vaccines.

It is the first of two jabs made in China under examination by the WHO to get the go-ahead.

The WHO announced at the end of last week the Emergency Use Listing (EUL) results for the vaccines from China's Sinopharm and Sinovac and the jab from U.S. firm Moderna would be published this week, after some delays.

Sinovac's CoronaVac jab is slightly behind on the regulatory path, but the WHO today announced it was "safe and effective" which lays the groundwork for the EUL.