AsianScientist (Nov. 20, 2020) – Hot off the heels of Pfizer’s and Moderna’s positive COVID-19 vaccine results, early trials of Sinovac’s CoronaVac have found that the vaccine is safe and induces an immune response in healthy volunteers. The study’s results were published in The Lancet Infectious Diseases.
Produced by Chinese biopharmaceutical company Sinovac Biotech Ltd, the CoronaVac vaccine was developed by growing SARS-CoV-2 in monkey cells and inactivating the virus with formalin. Notably, CoronaVac was the first COVID-19 vaccine to have reported broad protection in monkeys, neutralizing ten strains of the novel coronavirus in preclinical studies.
To assess the vaccine’s safety and ability to activate an immune response in humans, Phase I and II trials were carried out in China’s Jiangsu province. All participants were between 18 to 59 years old, and did not have any history of COVID-19 infection or visible symptoms at the time of recruitment.
Over 700 volunteers were recruited for Phases I and II. In each phase, volunteers were assigned one of two vaccination schedules: two injections given either 14 or 28 days apart. Within these two groups, participants were randomly assigned to receive either a low dose of the vaccine, a high dose or a placebo. Only mild side effects were initially reported, with the most common symptom being pain at the injection site.
Within a month after vaccination was completed in both phases, researchers detected antibody responses even at the lowest dose tested. However, an even more robust response was observed in volunteers who had followed the second vaccination schedule with a dose interval of 28 days.
Higher antibody levels were also observed during Phase II, after the introduction of an improved manufacturing process. Upon closer inspection, the researchers found that the new process caused the inactivated virus to carry on its surface a greater number of spike proteins recognized by our immune system. Despite this, it should be noted that even the highest antibody levels induced by CoronaVac were nearly three times lower than those observed in patients who had recovered from COVID-19.
Currently, Phase III trials of CoronaVac are underway in Brazil, Indonesia and Turkey. Findings from these trials will be crucial in determining if the immune response generated by the vaccine can sufficiently protect from SARS-CoV-2 infection.
Though the jury may still be out, the authors note that CoronaVac offers an attractive option compared to other vaccine candidates as it can be stored even in a standard refrigerator at 2 to 8°C and may remain stable for up to three years in storage.
“Our findings show that CoronaVac is capable of inducing a quick antibody response within four weeks of immunisation by giving two doses of the vaccine at a 14 day interval. We believe that this makes the vaccine suitable for emergency use during the pandemic,” said joint lead author Professor Zhu Fengcai from the Jiangsu Provincial Center for Disease Control and Prevention.
The article can be found at: Zhang et al. (2020) Safety, Tolerability, and Immunogenicity of an Inactivated SARS-CoV-2 Vaccine in Healthy Adults Aged 18–59 Years: A Randomized, Double-blind, Placebo-controlled, Phase 1/2 Clinical Trial.
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Source: The Lancet; Photo: Sinovac Biotech Ltd.
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