The Trump administration on Tuesday pledged to provide a future Covid-19 vaccine for free to “vulnerable” Americans unable to afford it. The remarks constitute the federal government’s most concrete pledge to date about vaccine affordability, which has emerged as a sticking point in recent congressional hearings and in legislation to address the pandemic. “For any American who is vulnerable, who cannot afford the vaccines, and desires the vaccine, we will provide it for free,” said a Trump administration official, speaking on the condition of anonymity, on a conference call with reporters.