Turkish officials announced Thursday that a vaccine made by Chinese company Sinovac has an efficacy rate of 91.25 percent. However, the finding is based on preliminary results from a small clinical study, and none of the data has been published in a journal or published online.
The announcement came a day after another ambiguous press conference in Brazil, also about Sinovac's vaccine. Officials there were expected to provide detailed results from another study, but they only reported that the vaccine had an efficacy rate of over 50 percent.
A total of 7,371 volunteers were involved in the Turkish study, but efficacy data from Infectious Disease Expert Serhat Unal was based on just 1,322 participants, of whom 752 received a real vaccine and 570 received the placebo.
Dr. Unal said that 26 of the volunteers who received the placebo developed Covid-19 while only three of the vaccinated volunteers became ill. He and his colleagues did not pass on their data in writing.
"Now we are sure that the vaccine is effective and safe for the Turks," said Fahrettin Koca, the health minister.
Sinovac did not make a public statement about the trial, nor did he comment on the trial in Brazil.
Dec. 25, 2020, 4:08 p.m. ET
The small number of volunteers that the Turkish researchers relied on to calculate effectiveness raised questions about the safety of their conclusions. The more people take part in a vaccine clinical study, the more statistical it is.
In contrast, Pfizer and BioNTech provided data on 36,523 people to show that the vaccine had a 95 percent effectiveness rate. For their vaccine, 162 people who received the placebo developed Covid, compared to eight people in the group who received the vaccine.
Turkey has signed a contract with Sinovac for 50 million doses of the vaccine. The first three million cans are due to arrive in Turkey on Monday, Koca said. Mr Koca said Turkey will also receive 4.5 million doses of the Pfizer BioNTech vaccine by the end of March. Around 1 million cans are expected to arrive by the end of January, he said.
CoronaVac, as Sinovac calls its vaccine, is made from killed coronaviruses. The method is one of the oldest for making vaccines that Jonas Salk used to make a vaccine against polio in the 1950s. After viruses are inactivated with chemicals, they can't make people sick, but they can stimulate the immune system to make antibodies that can provide long-term protection against live viruses.
Sinovac developed CoronaVac in early 2020 and then conducted a number of clinical studies. They published their results in November. There they reported that the vaccine appeared safe and produced an immune response against the coronavirus.
The company then moved on to phase 3 trials in Brazil, Indonesia and Turkey, three countries with high rates of Covid-19.
Health officials in Brazil said Wednesday that the Chinese vaccine had passed safety and effectiveness tests that would pave the way for its use in Brazil. However, they postponed the publication of detailed data from clinical studies in Brazil on which these results are based, citing a contractual agreement with Sinovac. Dimas Covas, the director of the butantane institute that conducted the trials, said a joint announcement could be made within two weeks.
"Today is a historic day for science and for Brazilian health," Jean Gorinchteyn, Sao Paulo State Minister of Health, told reporters at a press conference. "This will allow us to save the lives of millions of people, not just in Brazil, but around the world."