Argentina’s President Alberto Fernandez, who received two doses of Russia’s Sputnik V vaccine earlier this year, has tested positive for Covid-19, his doctor confirmed. Fernandez had earlier said that he was self-isolating after receiving a positive result from an antibody test. A polymerase chain reaction test, which is more definitive, had confirmed the result, according to a statement signed by Federico Saavedra, Fernandez’s long-time personal doctor and now a member of his medical staff. Fernandez is “stable, asymptomatic and with indicators within normal ranges, Saavedra said. The president had taken a test after running a fever and suffering a headache...