Brazil restarts late stage trials of Sinovac COVID-19 vaccine candidate

After a brief pause, Brazil restarted late stage trials for CoronaVac, the COVID-19 vaccine candidate developed by China's Sinovac Biotech Ltd.

Anvisa, the Brazilian health regulator, said in a press release on Wednesday that it had received and evaluated enough information "to allow the resumption of vaccination". The trials were suspended for less than two days.

"It is important to clarify that a suspension does not necessarily mean that the product under investigation lacks quality, safety or efficacy," said the regulator in a statement.

Anvisa paused the vaccine trial on Monday after reports linked the vaccine to the death of a participant under trial on Oct 29. The link does not exist after police found evidence of the person's suicide while industrialists refuted the unfounded reports.

"I can certainly say that the adverse event reported by the media is not related to Sinovac's vaccine," an industry source told China Daily.

Pearson Liu, director of brand management and public relations at Sinovac, pointed out in a statement on Tuesday: "Sinovac will continue to communicate with Brazil on this matter… we are confident in the safety of the vaccine," he said.

Sinovac is working with its Brazilian development partner, the Butantan Institute, a public research institute based in Sao Paulo. In a statement on Wednesday, Sinovac said the stoppage in the trial was caused by a miscommunication.

"We have learned that Anvisa failed to receive the data sent by Butantan Institute in time, and it urgently suspended the clinical study Nov 9," Sinovac said. "The Butantan Institute communicated with Anvisa on Nov 10, and the report from Data and Safety Monitoring Board was submitted to Anvisa on the same day."

"After evaluating the new data, Anvisa made a very timely decision to resume the clinical research," it said.

Anvisa approved phase III trials for CoronaVac on July 3. The aim is to recruit 9,000 patients to test the safety and efficacy of the vaccine. The vaccine is also being tested in Indonesia, Turkey and Bangladesh.

The Butantan Institute also announced in late October that it had received Anvisa's approval to import enough raw materials to produce 40 million doses of CoronaVac.

"This is another important step towards making CoronaVac available, which will be applied only after Anvisa's approval and registration as soon as the safety and effectiveness results are proven," the Butantan Institute said in a release.

Avisa added in its release: "The suspension and resumption of clinical studies are common events in clinical research and all studies aimed at registering medicines that are authorized in the country are previously evaluated by Anvisa in order to preserve the safety of the study volunteers."

Trial stoppages are not uncommon in phase III trials for vaccines. The trials for AZD-1222 by AstraZeneca Plc and Oxford University were temporarily paused in September and then restarted, also after reports of adverse effects.

Johnson & Johnson paused the trials for its COVID-19 vaccine candidate JNJ-7843635 in October, also due to an unexplained illness in a trial participant. The trial was later restarted.

Brazil's COVID-19 cases exceeded 5.7 million after registering 25,012 new cases in 24 hours by Tuesday, the Ministry of Health said. And 201 more deaths from the disease were reported, raising the national death toll to 162,829.

Sao Paulo Governor Joao Doria praised the regulator´s move to resume the trials. Just before the Anvisa pause, he had announced that a first batch of 120,000 doses of CoronaVac is expected to arrive in the country on Nov 20 for distribution in the state after it is approved.

"It was clear to the agency that the 'serious adverse event' that occurred with one of the volunteers had nothing to do with the vaccine," he said. "CoronaVac is safe, as has been proven in the tests done so far."

Doria told the media that that the Butantan Institute will manufacture the vaccine in its existing factories that are currently used to make influenza vaccine while a new manufacturing facility is built. This new facility should be ready by September 2021.

"Studies so far show that CoronaVac is the most promising and safest vaccine among vaccines against COVID-19," Doria said.

The writer is a freelance journalist for China Daily.