US buying additional 200M Moderna vaccine doses The U.S. government is buying another 200 million doses of Moderna’s COVID-19 vaccine, the company said Wednesday, which could be used for vaccinating children or to address variants of the virus if necessary. Why are more needed? The deal allows the Biden administration to receive different versions of the vaccine if necessary, for example if a modified vaccine is needed to fight a variant of the virus. The purchase is exercising an option for additional doses from the original contract with Moderna. "Importantly, the agreement gives the United States flexibility to choose which type of vaccine we will receive from Moderna if Moderna adjusts its formulation, for example, for pediatric vaccines or to address variants," an administration official said.