The trial with 700 patients, which took place in April and May, was not designed to assess efficacy, but did show it could provide sufficient protection against the new coronavirus, the biotech said.

Sinovac’s trial was set up as a method of assessing what dose to use in Phase 3 and led the company to determine that the 3-μg dose of the candidate dubbed CoronaVac was the right one to be tested in Phase 3, now ongoing.

Information about this Chinese candidate – one of three under development in the People’s Republic – has been overshadowed by a political dispute in Brazil that led to a Phase 3 trial there being stopped in late October after a volunteer died.

The death was later found to be unrelated to the trials with the Chinese candidate, which president Jair Bolsonaro, an admirer of US president Donald Trump, called a “communist vaccine.” The Brazilian Butantan Institute, which played a role in the vaccine’s development, began the trial last July and was targeting recruitment of 130,000 volunteers.

In ordering the restart, Brazil's National Health Surveillance Agency Anvisa said an evaluation of the data and a risk assessment led to the conclusion that the vaccine was not unsafe, as the president had claimed. It is unclear whether the studies in Brazil have actually resumed, but Sinovac is also undertaking Phase 3 trials in Turkey and Indonesia, and efficacy data from these will later flow into the published results.

Apart from Bolsonaro’s apparent wish to support the Trump administration’s dispute with China, sources told international news media that the Brazilian leader wanted to stop the Chinese studies in part to win points in a political argument with the governor of Sao Paulo.

Gov. Joao Doria, who is expected to run against Bolsonaro in the country's next presidential elections in 2022, called CoronaVac "the safest, the one with the best and most promising rates" among all the vaccines tested in Brazil,” based on early results.

In China (as in Russia) drugmakers have been seen as administering experimental vaccines to tens of thousands of people since July under a government-approved emergency use authorization, without waiting for Phase 3 data.

Indonesia recently said it planned to administer Sinovac's vaccine to 9 million people in the third week of December under an emergency use authorization approval from drug regulation authorities there.

Author: Dede Williams, Freelance Journalist