New York, July 28 : Pharmaceutical company Moderna has begun a phase-3 clinical trial to evaluate an investigational vaccine known as mRNA-1273 designed to protect against Covid-19 virus. The trial, which will be conducted at the US clinical research sites, will include 30,000 participants who do not have Covid-19. "Results from early-stage clinical testing indicate the investigational mRNA-1273 vaccine is safe and immunogenic, supporting the initiation of Phase 3 clinical trial," said Anthony S. Fauci from National Institute of Allergy and Infectious Diseases (NIAID) in the US. "This scientifically rigorous, randomised, placebo-controlled trial is designed to determine if the vaccine can prevent Covid-19 and for how long such protection may last," Fauci added. The mRNA-1273 is designed to induce neutralising antibodies directed at a portion of the coronavirus "spike" protein, which the virus uses to bind to and enter human cells. Moderna's vaccine was co-developed by the Cambridge University and the NIAID, part of the National Institutes of Health (NIH). According to the researchers, the mRNA-1273 vaccine candidate will be tested at approximately 89 clinical research sites in the US, 24 of which are part of the NIH Coronavirus Prevention Network (CoVPN). Investigators will use public health data and incidence trajectory modelling to identify sustained high-incidence areas and emerging hot zones, so sites near these locations can be prioritised for enrollment. The Phase-3 blinded trial will evaluate the safety of mRNA-1273 and determine if the vaccine can prevent symptomatic Covid-19 after two doses. Volunteers will receive two intramuscular injections approximately 28 days apart. Participants will be randomly assigned to receive either two 100-microgram injections of mRNA-1273 or two shots of a saline placebo. The trial also seeks to answer if the vaccine can prevent death caused by COVID-19 and whether just one dose can prevent symptomatic COVID-19, among other objectives. Researchers will collect and analyse blood samples to detect and quantify immune responses to SARS-CoV-2. Investigators will closely monitor participant safety. They will call participants after each vaccination to discuss any symptoms and will provide participants with a diary to record symptoms and a thermometer for temperature readings. Study investigators will regularly review trial safety data. An independent data and safety monitoring board (DSMB) will review blinded and unblinded data--including safety data and cases of Covid-19 in both groups--at scheduled data review meetings. Meanwhile, Moderna has received an additional $472 million award from the US government's Biomedical Advanced Research and Development Authority (BARDA) for Phase-3 clinical trial of its Covid-19 vaccine candidate. /IANS