Because of greater-than-expected demand, vaccine has been back ordered for the public sector throughout most of 2001. In August, the situation worsened when facility and product testing-related limitations at the manufacturer's production sites halted distribution for several weeks. Under a full vaccination schedule, approximately 1.5 million doses are needed per month; the manufacturer estimates that 90% of the doses are used for the 4-dose infant vaccination series, and 10% are used for catch-up vaccination. During September, approximately 700,000 doses were distributed (47% of the 4-dose infant schedule), and in October, approximately 600,000 doses were distributed (40%). The manufacturer anticipates the distribution of approximately 1.2 million doses per month during November 2001-March 2002 (86%) and approximately 2.0 million doses per month during April 2002-mid-2002 (142%).