WHO experts have voiced "very low confidence" in data provided by Chinese state-owned drugmaker Sinopharm on its COVID-19 vaccine regarding the risk of serious side-effects in some patients, but overall confidence in its ability to prevent the disease, a document seen by Reuters shows.
A World Health Organization spokesman said that the document on Sinopharm vaccine BBIBP-CorV was "one of many resources" on which recommendations are made, tentatively scheduled to be issued later this week.
In Beijing, Sinopharm was not immediately reachable for comment outside working hours.
The "evidence assessment" document was prepared by the WHO's Strategic Advisory Group of Experts (SAGE) for its evaluation of the Sinopharm shot, authorised by 45 countries and jurisdictions for use in adults, with 65 million doses administered. The experts review evidence and give recommendations on policy and dosages associated with a vaccine.
The document includes summaries of data from clinical trials in China, Bahrain, Egypt, Jordan and the United Arab Emirates.
Vaccine efficacy in multi-country Phase 3 clinical trials was 78.1% after two doses, the document said. This was a slight drop from 79.34% announced previously in China.
"We are very confident that 2 doses of BBIBP-CorV are efficacious in preventing PCR confirmed COVID19 in adults (18-59 years)," the document said.
But it added: "Analysis of safety amongst participants with comorbidities (was) limited by the low number of participants with comorbidities (other than obesity) in the Phase 3 trial."
Among "evidence gaps", it cited data on protection against severe disease, duration of protection, safety for use in pregnant women and in older adults and identification/evaluation of rare adverse events through post-authorisation safety monitoring.
"We have very low confidence in the quality of evidence that the risk of serious adverse events following one or two doses of BBIBP-CorV in older adults (≥60 years) is low," it said.
"We have very low confidence in the quality of evidence that the risk of serious adverse events in individuals with comorbidities or health states that increase risk for severe COVID-19 following one or two doses of BBIBP-CorV is low," it added.
The SAGE analysis was prepared as a WHO technical advisory group currently reviews the vaccine for an emergency use approval, which would not only pave the way for its use in the global COVAX vaccine sharing platform but also provide a crucial international endorsement for a vaccine developed in China.
A WHO spokesman said that a decision on the listing was not expected on Wednesday.