Health officials have spent months trying to convince Americans to get the swine flu vaccine, but it appears there is not enough to go around.
In Iowa, more than 2,000 free vaccines were administered in less than four hours.
The Centers for Disease Control says production of the H1N1 vaccine has fallen behind schedule. They hoped 40 million doses would be ready by the end of the month, but fewer than 30 million doses will be ready by then.
"Vaccine production is pretty complex, and it is taking a bit longer than we would hope," Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases, said in a press conference Friday.
Since April, 86 children have died from H1N1 in the U.S.
Schuchat said, "Those are very sobering statistics."