Turkey’s Sinovac test results jar with Brazil’s as confidence in vaccine undercut

Medical experts are warning that fragmental releases of efficacy data for a Chinese-made COVID-19 vaccine could undermine confidence in the shot, Reuters reported on Monday.

Turkish authorities said on Thursday that late-stage trials for CoronaVac, the vaccine developed by Sinovac Biotech, have proven 91.25 percent effective based on an interim analysis. However, Brazilian researchers said the same day that the vaccine’s efficacy was between 50 percent and 90 percent.

Experts cited by Reuters said it was not unusual for a vaccine to show different efficacy rates in various settings due to several factors, such as trial protocols, data size and population, but the release of the CoronaVac results raised questions.

“You really want the data to be compelling at first presentation; this is what Pfizer and Moderna achieved, AstraZeneca less so,” Jerome Kim, head of the International Vaccine Institute, a Seoul-based non-profit agency devoted to research in vaccines, told Reuters.

“With multiple ‘leaks’ of data and suggestions of this or that you don’t see the same effect with Sinovac; perhaps the final presentation in January will be more compelling.”

The data for the Turkish vaccine trial is based on an analysis of 1,322 participants which included 29 infected people, and efficacy evaluations were made 14 days after the second dose was administered, Reuters said.

“It’s difficult to determine how well (the) Sinovac vaccine works based solely on 29 coronavirus cases,” Kim said. “It would be good to have more volunteers and more infections, which would boost the robustness of the efficacy data.”

Turkey released the interim evaluation because it was seeking to grant emergency use authorisation for a COVID-19 vaccine, Reuters said. The Health Ministry has reported a near-daily record of deaths per day related to the coronavirus since Nov. 20.

Dicky Budiman, an epidemiologist at Queensland’s Griffith University, warned greater scrutiny on data compilation and analysis was required for COVID-19 vaccines developed in China due to its inconsistent safety track record.

“This should be analysed very clearly and transparently. And transparency is one of the biggest concerns for China, especially with their vaccine and also because of their track record,” Budiman told Reuters.

“So, this is one of the very important and crucial times for China to show the world how they have improved the quality of their vaccines ... This is something they have to explain to the world through, of course, scientific papers.”