India said on Thursday it had curbed an increase in COVID-19 infections, with a fifth of its districts reporting no new cases for a week, even as its immunisation campaign has covered 2.4 million people. The country of 1.35 billion has recorded the highest number of cases in the world after the United States, though the rate of infection has come down significantly since a mid-September peak. Some studies have suggested pockets of India have attained herd immunity through natural infection.