The Centre today said the country needs to buy more time to vaccinate more and more Indians. If the containment measures, Covid-appropriate behaviour and vaccination pace slacken, cases can rise again, it added; The Pfizer vaccine's efficacy drops against the Delta variant, says Lancet study; The Covid positivity rate comes down to almost 7 per cent; RBI cuts growth forecast to 9.5 per cent; and other top news of the day.