Countries would be better off waiting until Phase 3 clinical trials, which test the safety and efficacy of an experimental vaccine in tens of thousands of people, are completed before rolling out the vaccine for wider use, World Health Organization Chief Scientist Soumya Swaminathan said on Monday.

Although some countries, including China, Russia and the United States, have approved or are considering COVID-19 vaccine candidates for emergency use, Swaminathan underlined that emergency use regulation is only a “temporary solution,” and countries needed more data before deciding to roll out the vaccine to the public.

“It is only a temporary solution, and the longer term solution is really completing those Phase 3 trials, which will provide the confidence for those vaccine candidates to be actually used in the millions of doses,” said Swaminathan. 

“We’d like to see data on both safety and efficacy in significant numbers of people,” she added. “So the phase one and two studies are usually done in a few dozen individuals. And while these give you some idea about safety and… the immunogenicity of the vaccine, what we are really looking for is signals for efficacy and safety during longer follow-up [in a larger group].” 

She was responding to a query about reports of SinoVac, a Chinese company at the forefront of COVID-19 vaccine development, allowing  its employees and their families to use the investigational vaccine before Phase 3 trials have concluded. China had already in July approved the SinoVac vaccine candidate for emergency use, although few details about the regulation are available. 

The comments also follow the publication of an op-ed by Jeremy Farrar, head of the research foundation the Wellcome Trust, that warned governments to “temper their optimism” about a “magic bullet” COVID-19 vaccine. Farrar further warned that governments must avoid compromising safety in favor of speed in vaccine development. 

Still, Swaminathan said that national authorities still have the right to decide what to do, but they should be monitoring use of the vaccine closely, and doing it under a clear emergency use authorization. 

“National regulatory authorities have the mandate and the power to allow use of medical products within their own jurisdictions under certain conditions in an emergency, and a pandemic is one of those conditions,” she said. “Hopefully this is done under monitored conditions, it’s done under what we call the emergency use of products – under research settings where people who are given the vaccine are followed regularly are assessed at periodic intervals.” 

A WHO team in China is working directly with regulatory authorities to share data on the vaccine, and to make sure the vaccine meets WHO’s standards before moving forward to ensure international access, added Mariangela Simao, WHO assistant general for Access to Medicines, Vaccines and Pharmaceuticals.