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The Phase 1/2 clinical trial of a candidate vaccine product (CoronaVac) involved more than 700 healthy volunteers, aged 18 to 59, recruited in China between April 16 and May 5.
“The vaccine appeared to be safe and well tolerated at all doses tested. The most reported side effect was pain at the injection site, “reads the information released by the Lancet.
14 days after the final dose, “robust responses” of antibodies were detected after two injections of the candidate vaccine, 14 days apart, even at the lowest dose tested.
Vaccine-induced antibody levels were lower than those seen in people infected and cured of covid-19 disease caused by the new coronavirus, but the researchers say they still hope the vaccine can provide protection against the virus.
The main objective was to evaluate the immune response and the safety of the vaccine. The study was not designed to evaluate efficacy in preventing SARS-CoV-2 infection.
The results of the early phase clinical trial of the candidate vaccine based on the whole inactivated SARS-CoV-2 virus (CoronaVac) were published in The Lancet Infectious Diseases, revealing that the formulation appears safe and induces an antibody response in healthy people.
Antibody responses can be induced within 28 days of the first immunization by administering two doses of the candidate vaccine 14 days apart.
The study also made it possible to identify the ideal dose to generate the best antibody response, taking into account side effects and production capacity, which will be further investigated in other studies already underway.
Scientists believe CoronaVac may provide sufficient protection against Covid-19, based on the experience of other vaccines and data from preclinical monkey studies.
The study was not designed to evaluate the efficacy and the results of the phase 3 studies will be crucial in determining whether the immune response generated by CoronaVac is sufficient to protect against SARS-CoV-2 infection.
“Furthermore, the persistence of the antibody response needs to be tested in future studies to determine the duration of any protection,” the paper states.
Further studies will be needed to test the candidate vaccine in other age groups, as well as in people with pre-existing diseases.
“Our results show that CoronaVac is able to induce a rapid antibody response within four weeks of immunization by administering two doses of the vaccine within 14 days. We believe this makes the vaccine suitable for emergency use during the pandemic. long-term, when the risk of covid-19 is lower, our results suggest that giving two doses one month apart instead of two weeks may be more appropriate to induce stronger and potentially more lasting immune responses, “explained Fengcai Zhu, co-author of the study, of the Jiangsu Provincial Center for Disease Control and Prevention, Nanjing, China, arguing the need for further studies.
CoronaVac is one of 48 COVID-19 vaccine candidates currently in clinical trials. It is a chemically inactivated complete viral vaccine based on a SARS-CoV-2 strain originally isolated from a patient in China.
The covid-19 pandemic has caused at least 1,328,048 deaths resulting from more than 55 million cases of the infection worldwide, according to a report by the French agency AFP.
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