BOGOTA, Colombia and VANCOUVER, Canada – Anvisa, Brazil’s health care surveillance agency, restarted phase III trials for Coronavac, the COVID-19 vaccine candidate developed by China-based Sinovac Biotech Ltd., after a suspension of just two days.

“Anvisa understands that it has sufficient subsidies to allow the resumption of vaccination,” the regulator said on Nov. 11. Anvisa said it plans to continue monitoring “the possible relationship of causality” between an unexpected serious adverse event and the vaccine.

The regulator said it had made the quick decision to pause the trials because it did not have enough data related to the trial or the adverse effect. The agency explained that “the precautionary principle, which provides for prudence, decision-making caution when scientific knowledge is not able to rule out the possibility of harm.”

The suspension the trial triggered an intense political exchange between the federal government and the state government of Sao Paulo, which has been a big backer of the Chinese vaccine.

Anvisa stopped the trials on Nov. 9 after reports surfaced of an adverse event on Oct. 29. According to Sinovac, the regulator had not received data about the adverse effect from its Brazilian development partner the Butantan Institute. Without the data, the regulator decided to stop the trial. It reversed the decision after receiving and evaluating the data from Butantan the next day.

“We look forward to concluding the following clinical research as soon as possible under the strict governance and monitoring by Anvisa,” Sinovac said. “We are confident in the safety of the vaccine, fully understand and appreciate Anvisa's strict supervision and timely resumption of the clinical studies.”

Anvisa green-lighted the start of phase III trials in Brazil to test Coronavac’s efficacy and safety on July 3.

Sinovac´s subsidiary, Sinovac Life Sciences, partnered with Butantan, a public research institution in Sao Paulo, to develop the vaccine.

The study aims to recruit 9,000 health professionals taking care of COVID-19 patients, from the states of Sao Paulo, Rio Grande do Sul, Minas Gerais and Paraná, in addition to the Federal District.

The state of Sao Paulo expects a first batch of Coronavac vaccines to arrive in the country on Nov. 20, Governor Joao Doria announced earlier this month.

“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,” Doria said in a brief statement published on his social media. “Coronavac is safe, as has been proven in the tests done so far.”

Despite the governor’s comments, Anvisa said that it continues the investigation of the possible relationship between the serious adverse event and the vaccine candidate.

Should the vaccine be approved, Butantan plans to manufacture about 40 million doses in its existing facilities and build another factory by September 2021.

The short-lived controversy in Brazil was yet another issue for Sinovac. Shares of the Nasdaq-listed (NASDAQ:SVA) company have been halted for trading since February 2019. The freeze was the result of a push by Chairman and Chief Executive Yin Weidong to undertake a buyout as far back as 2016. Yin was outbid by a consortium led by the company’s minority joint-venture partner while 1Globe Capital, a Boston-based investment firm, built a 16% stake in the company. The back and forth led to infighting and the emergence of competing boards of directors.

The problems exploded again in 2018 after efforts to dilute the value of the company’s shares.

There are now ongoing court battles to determine the legitimate board of directors. For the time being, the shares of the company remain frozen.

Ultimately, investors may not be able to capitalize should the company’s COVID-19 vaccine candidate prove successful and the company get a share of a market expected to be worth as much as $40 billion over the next year alone.

The value of shares of Sinovac’s Chinese competitor Cansino Biologics Inc. (HKG: 6185), which has its own vaccine under development, are up more than 150% this year.