With more than 20 vaccines in human trials, the move will stir concerns that rich countries, including the United States and European Union members, are scooping doses in advance, potentially to the detriment of poorer nations.

Last week, Britain struck deals for 30 million doses of an experimental BioNTech/Pfizer vaccine, and a deal in principle for 60 million doses of Valneva’s potential shot.

That followed a previously announced pact with AstraZeneca (AZN.L) for 100 million doses of its potential vaccine, being developed in partnership with Oxford university.

The Sanofi/GSK vaccine combines Sanofi’s S-protein COVID-19 antigen and GSK’s pandemic adjuvant technology, and the first clinical trials are expected in September.

Adjuvants are efficacy boosters that play a vital role in many traditional vaccines. Sanofi and GSK’s vaccine uses a different approach than either Oxford/AstraZeneca or Pfizer/Biontech vaccines.

Sanofi and GSK said talks with the European Union, Italy and France to supply their vaccine were ongoin

The two firms hope to clinch a deal soon to provide 300 million doses to the EU, though two sources told Reuters that negotiations had stalled.

Britain decided against joining the EU’s vaccine purchase scheme in order to strike its own deals.