The United States is tying payments for COVID-19 vaccines to timing milestones for production and approval, according to public documents and a Trump administration official, putting pressure on drugmakers including Moderna Inc to meet ambitious targets. In a deal with Moderna announced this week, federal agencies negotiated a sliding scale of payments. The Cambridge, Massachusetts, biotech’s $1.5-billion deal pays out in full if its vaccine receives regulatory clearance by January 31, 2021, according to filings. It receives $1.2 billion, if it falls short of that timing goal. Moderna also receives $600 million when it can demonstrate it has built out industrial-scale manufacturing capabilities for its vaccine, even if that happens before the drug is authorized by regulators, the filings show.US government payments to other drugmakers are also conditional on launching clinical trials no later than early fall and building out manufacturing capabilities by the end of the year, two senior administration officials told Reuters, adding that terms varied by company. The deal terms add financial risk for the drugmakers and increase pressure for speed that has worried some public health advocates. HHS and Moderna declined comment; other drugmakers had no immediate comment on Friday.Other drugmakers did not publicly reveal details on the specific terms of their agreements with the US government, though Pfizer has said its deal with the government for its joint vaccine with BioNTech only pays out if it receives regulatory approval.