Johnson & Johnson has begun phase three global trials of its single-dose Covid-19 vaccine with up to 60,000 volunteers from US, South Africa, Argentina, Brazil, Chile, Colombia, Mexico and Peru.The Covid-19 vaccine is being developed by its Janssen Pharmaceutical Companies."Johnson & Johnson will develop and test its COVID-19 vaccine candidate in accordance with high ethical standards and sound scientific principles," the company said in a statement.The dosing up marks the first big US trial of an inoculation that may work after just one shot.A few other vaccines in the U.S. — including shots made by Moderna Inc.
and Pfizer Inc. — and others in other countries are already in final-stage testing.If enrollment goes as expected, the trial.