A senior official of China's Sinovac Biotech Ltd. defended the company's vaccine Thursday after trials in Brazil indicated it was much less effective than previous data had suggested.
The Sinovac vaccine's overall efficacy rate in Phase 3 trials in Brazil was found to be just slightly over 50% because the clinical trial was conducted on health workers at high risk of infection, the company's senior director, Yin Veydong, said at a press conference in Beijing, according to Bloomberg.
Yin noted that participants in clinical trials of vaccines that achieve high rates of effectiveness, such as the vaccine developed by BioNTech-Pfizer, are mostly ordinary citizens with a relatively low risk of infection.
The Butantan Institute, which conducted clinical trials of the Sinovac vaccine in Brazil, announced last week that the vaccine was 78% effective against "mild to severe" COVID-19 cases.
In the trials, more than 12,000 health workers were vaccinated in two doses.
It was noted that COVID-19 was observed in 288 of the participants in the trial, of which 128 were given the actual vaccine formula and 160 were given a placebo (fake formula).
The Butantan Institute reported yesterday that the overall effectiveness of Sinovac's CoronaVac vaccine was 50.38%.
In trials conducted in Turkey with fewer participants than in Brazil, the vaccine developed by Sinovac was reported to be 91.5% effective in preventing the disease.
According to a preliminary assessment report prepared for Phase 3 clinical trials launched on Sept. 14, it was stated that only three of the 752 people who received the actual vaccine in the trial, in which two doses were given to 1,322 volunteers, and 26 of the 570 people who received the fake formula were infected with COVID-19.
Six of the 26 cases of COVID-19 that received the placebo experienced a serious coronavirus infection that required hospitalization, while three cases of vaccination survived the disease with mild symptoms.
Sinovac's vaccine candidate formula contains a virus component -- a "neutralized" version of COVID-19.
In this way, the vaccine aims to revive the body's natural defenses against the weakened virus, creating an immune response.
Phase 3 clinical trials of the vaccine candidate, which was approved for emergency use in China in July, were conducted in Brazil, Chile, Indonesia and Turkey.
The Butantan Institute, which Sinovac cooperated with in clinical trials in Brazil, reported on Dec. 21, 2020 that the effectiveness level in the results received so far exceeded 50%, the minimum required for regulatory approval.
Health officials in the country, where clinical trials were conducted for five different vaccines at the same time, announced that the Sinovac vaccine had the least side effects.
CoronaVac testing on humans began on Sept. 17 in Turkey as part of the third stage trials.
Turkey's Health Minister Fahrettin Koca announced on Nov. 25 that a contract had been signed to purchase a total of 50 million doses in the winter from an inactive vaccine candidate originating in China.
The vaccine, the first batch of which arrived in Turkey on Jan. 30, began to be administered yesterday after being tested by the Turkish Pharmaceutical and Medical Device Agency.
Since December 2019, the COVID-19 pandemic has claimed more than 1.98 million lives in 191 countries and regions.
Over 92.7 million cases have been reported worldwide, with recoveries now over 51.1 million, according to figures compiled by US-based Johns Hopkins University.
The US, India and Brazil remain the worst-hit countries in terms of cases.
