Chinese President Xi Jinping called on Saturday for more effort and unity as the country enters a “new phase” in its approach to combating the pandemic, in his first comments to the public on COVID-19 since his government changed course three weeks ago and relaxed its rigorous policy of lockdowns and mass testing. China’s abrupt switch earlier this month from the “zero-COVID” policy that it had maintained for nearly three years has led to infections sweeping across the country unchecked. It has also caused a further drop in economic activity and international concern, with Britain and France becoming the latest...