The US administration will provide as much as $2.1 billion to Covid-19 vaccine partners Sanofi and GlaxoSmithKline Plc, the biggest US investment yet in fast-tracking shots and snapping up supplies.

Part of Operation Warp Speed, the funding will support clinical trials and manufacturing while allowing the US to secure 100 million doses of the shot, if it’s successful, the companies said on Friday. The country has an option to receive an additional 500 million doses longer term. Glaxo shares traded 1.6 per cent higher in London, with Sanofi up 1.4 per cent in Paris. The deal follows billions of dollars of US commitments to other experimental vaccines — all still needing to show their effectiveness in testing— and may stoke concerns that some countries will be left behind. Vaccines are seen as the key to leading the world out of the pandemic that has killed about 675,000 people in a matter of months.Bloomberg