But Dr. Anne Schuchat, the director of the National Center for Immunization and Respiratory Diseases, said the estimate gives a "more accurate picture" of the scale of the pandemic.

CNN: H1N1 death toll estimated at 3,900 in U.S.

But due to manufacturing delays, "we think at most it will be 10 to 12 million doses less, " said Dr. Anne Schuchat, CDC's director of the National Center for Immunization and Respiratory Diseases.

CNN: CDC: Production of H1N1 flu vaccine lagging