Continued shortage of Haemophilus influenzae Type b (Hib) conjugate vaccines and potential implications for Hib surveillance--United States, 2008.

In December 2007, Merck & Co., Inc. (West Point, Pennsylvania) announced a voluntary recall of certain lots of two Haemophilus influenzae type b (Hib) conjugate vaccines, PedvaxHIB (monovalent Hib vaccine) and Comvax (Hib-HepB vaccine) and suspended production of both vaccines, disrupting the U.S. supply of Hib vaccine. When the recall was announced, Merck projected restoration of these vaccines to the U.S. market in late 2008. To ensure that enough vaccine would be available for all U.S. children to complete the primary Hib vaccination series, on December 18, 2007, CDC recommended that providers defer the booster dose of Hib vaccine (scheduled for administration at age 12-15 months) for all children except those at increased risk for invasive Hib disease. On October 17, 2008, Merck announced that restoration of the two vaccines to the market would be delayed until mid-2009. Because the continued delay might result in an increase in Hib disease, national surveillance for invasive Hib disease has become particularly important. To assess the current status of surveillance for Hib nationally, CDC reviewed 4,657 cases of invasive H. influenzae infection reported during January 2007-October 2008, including 748 cases among children aged <5 years. Of those 748 cases, 45 (6.0%) were Hib (serotype b), and 278 (37.2%) were missing serotype information. The continued vaccine shortage heightens the need for timely reporting and investigation of H. influenzae cases and accurate serotyping of all invasive H. influenzae isolates in children aged <5 years.