A health worker prepares a dose of Sinovac vaccine at a vaccination site in Manila, the Philippines on March 31, 2021. (Xinhua/Rouelle Umali)

The World Health Organization (WHO) validated on Tuesday the CoronaVac COVID-19 vaccine developed by Chinese pharmaceutical company Sinovac Biotech for emergency use.

WHO recommends the vaccine for use in people 18 years and older, in a two-dose schedule with a spacing of two to four weeks, according to a statement.

The efficacy results showed that the Sinovac vaccine prevented symptomatic disease in 51 percent of those vaccinated, and prevented severe COVID-19 and hospitalization in 100 percent of the studied population, according to the WHO's Strategic Advisory Group of Experts on Immunization (SAGE).

However, as few people over 60 years old were enrolled in clinical trials, the WHO said the Sinovac vaccine's efficacy could not be estimated in this age group.

"There is no reason to believe that the vaccine has a different safety profile in older and younger populations," the statement said, adding that the WHO is not recommending an upper age limit for the vaccine, because data collected in multiple countries and supportive immunogenicity data suggest the vaccine is likely to have a protective effect in older persons.

As in the cases of previously validated vaccines, WHO recommends that countries using the Sinovac vaccine in older age groups conduct safety and effectiveness monitoring to verify the expected impact and contribute to making the recommendation more robust for all countries.

"The world desperately needs multiple COVID-19 vaccines to address the huge access inequity across the globe," said Mariangela Simao, WHO assistant-director general for Access to Health Products, in the statement. "We urge manufacturers to participate in the COVAX Facility, share their know-how and data and contribute to bringing the pandemic under control."

The Sinovac vaccine is the second one from China that has been included in WHO Emergency Use Listing, following the Sinopharm vaccine which was validated earlier last month.

Apart from the two Chinese vaccines, the WHO has previously listed the COVID-19 vaccine developed by Pfizer/BioNTech, two versions of AstraZeneca/Oxford vaccine, the Janssen vaccine, and the Moderna vaccine for emergency use.