NEW YORK – The push to inoculate Americans against the coronavirus is hitting a roadblock: A number of states are reporting they are running out of vaccine, and tens of thousands of people who managed to get appointments for a first dose are seeing them canceled.About half of the 31 million doses distributed to the states by the federal government have been administered so far, though only about 2 million people have received the two doses needed for maximum protection against COVID-19, according to the Centers for Disease and Control and Prevention.The full explanation for the apparent mismatch between supply and demand was unclear, but last week the U.S.