The United States on Wednesday promised to buy 500 million more Covid-19 vaccine doses to donate to other countries as it comes under increasing pressure to share its supply with the rest of the world.

The White House is hosting a four-hour virtual summit aimed at boosting global vaccination rates and the administration of American President Joe Biden wants to show it is leading by example.

“To beat the pandemic here we need to beat it everywhere,” Biden said, kicking off the summit, which includes leaders from Canada, Indonesia, South Africa and Britain, as well as World Health Organization (WHO) head Tedros Ghebreyesus.

“This is an all hands on deck crisis,” he said of the pandemic that has raged since early 2020, killing at least 4,913,000 people.

The additional vaccines will bring US donations to the rest of the world to more than 1.1 billion doses. The vaccines from Pfizer and BioNTech will be made in the United States and shipped to low and lower middle-income countries starting in January.

Bats with Covid-like viruses found in Laos

Scientists have found another clue to the origin of the Covid-19 virus, with bats living in caves in Laos found to be carrying a similar pathogen that experts suggest could potentially infect humans directly.

Researchers from France’s Pasteur Institute and the National University of Laos said their findings showed that viruses genetically close to the SARS-CoV-2 virus “exist in nature” among bat species found in the limestone caves of northern Laos, which neighbours China.