U.S. researchers at the Center for Pharmaceutical Research have opened another safety test of an experimental Covid-19 vaccine and this one uses a skin-deep shot instead of the usual deeper jab. The vaccine has been developed by biotechnology company Inovio Pharmaceuticals. The experiment will test two doses in 40 healthy volunteers at the Kansas City research lab and the University of Pennsylvania. Researchers packaged a section of the virus' genetic code inside a piece of synthetic DNA. Injected as a vaccine, the cells act as a mini-factory to produce harmless protein copies and the immune system makes protective antibodies against them. Even if the research goes well, it is expected to take over a year before the vaccine could be widely available.