US lawmakers and nonprofit groups on Friday heaped pressure on the Biden administration to back a temporary patent waiver for Covid-19 vaccines to help poor countries contain the pandemic. The groups delivered a petition signed by two million people, adding to separate letters already sent to US President Joe Biden by a group of senators, House of Representatives Speaker Nancy Pelosi, nearly 100 members of the House and 60 former heads of state and 100 Nobel Prize winners. Critics argue that waiving IP rights could reduce the safety of vaccines worldwide, and say other issues - such as improving distribution networks - are far more urgent priorities.