The World Health Organisation approved on Tuesday Sinovac's COVID-19 vaccine for emergency use for adults 18 and over.

It is the second such authorisation the global body has granted to a Chinese company, after Sinopharm.

In a statement Tuesday, the UN health agency said data submitted to its experts showed that two doses of the vaccine prevented people from getting symptoms of COVID-19 in about half of those who got the shot.

WHO said there were few older adults enrolled in the research, so it could not estimate how effective the vaccine was in people over 60.

“Nevertheless, WHO is not recommending an upper age limit for the vaccine,” the agency said, adding that data collected from Sinovac’s use in other countries “suggest the vaccine is likely to have a protective effect in older persons.”

In April, a study published by a team of scientists in Brazil confirmed a previously reported efficacy rate of over 50% for Sinovac. A real-world study in Chile in April found an efficacy rate of 67%.

WHO also gave the green light to the COVID-19 vaccines developed by Pfizer-BioNTech, AstraZeneca, Moderna and Johnson & Johnson.

Eyes on developing countries

WHO’s authorisation means the vaccine can be bought by donors and other UN agencies for use in developing countries, including in the UN-backed initiative to distribute COVID-19 vaccines globally known as COVAX.

“The world desperately needs multiple COVID-19 vaccines to address the huge access inequity across the globe,” said Dr Mariângela Simão, WHO Assistant-Director General for Access to Health Products.

“We urge manufacturers to participate in the COVAX Facility, share their know-how and data and contribute to bringing the pandemic under control.”

The effort has been slowed considerably after its biggest supplier in India said it would not be able to provide any more vaccines until the end of the year due to a recent spike in infection in the south Asian nation.

To date, there is no confirmed deal for Sinovac doses with COVAX.

EU still awaits regulator decision

In May, Europe's drug regulator began an expedited review process for the Sinovac vaccine, but it's unclear when a decision might be made about its possible authorisation for the 27-nation bloc.

Hundreds of millions of Chinese vaccines have already been delivered to dozens of countries around the world through bilateral deals.

Many developing nations scrambled to secure supplies after rich countries reserved the vast majority of doses from Western pharmaceutical makers.

While China has five vaccine shots in use, the majority of its exports abroad come from two companies: Sinopharm and Sinovac. The Chinese vaccines are “inactivated” vaccines, made with killed coronavirus.

Most other COVID-19 vaccines being used around the world are made with newer technologies that instead target the “spike” protein that coats the surface of the coronavirus.