Merck Temporarily Unable to Ship Hib Vaccine

Merck & Co. Inc. recently notified the CDC (1-page PDF; About PDFs) that its Haemophilus influenzae type b conjugate vaccine, sold as PedvaxHIB, currently is unavailable for shipment. Merck said it anticipates the vaccine, which is indicated for routine immunization against invasive disease caused by H. influenzae type b in infants and children ages 2-71 months, will become available again sometime in the first quarter of 2008; the exact timing will depend on resolution of a manufacturing issue.

Merck further reported that the company has an adequate supply of its combination H. influenzae type b/hepatitis B vaccine, COMVAX, to meet historical demand, but not to meet additional demand. COMVAX is indicated for immunization of infants and children ages 6 weeks to 15 months against invasive H. influenzae type b disease and against infection caused by all known subtypes of hepatitis B virus in infants born to hepatitis B surface antigen-negative mothers. It should be administered at ages 2 months, 4 months and 12-15 months.

A multifaceted contingency plan is being implemented by the CDC, Merck and sanofi pasteur, another Hib vaccine manufacturer, so the CDC's Advisory Committee on Immunization Practices has not called for any changes in overall Hib immunization recommendations at this time.

The CDC has announced that it will release limited amounts of PedvaxHIB from the CDC vaccine stockpile. Doses for the private sector will be made available through Merck, and those for the public sector will be handled through CDC vaccine contracts.

The quantity of stockpiled vaccine to be released will not be sufficient to meet historical demand for PedvaxHIB (PRP-OMP [polyribosylribitol phosphate polysaccharide conjugated to a meningococcal outer membrane protein]), according to the CDC. Therefore, sanofi pasteur will work to provide additional doses of its H. influenzae type b conjugate vaccine, ActHIB (PRP-T [polyribosylribitol phosphate polysaccharide conjugated to tetanus toxoid]), to help meet demand. ActHIB is indicated for the immunization of infants and children ages 2-18 months to prevent invasive H. influenzae disease.

CDC officials estimate that for the immediate future, providers of Hib vaccine will need to use PRP-T vaccine to meet approximately one-half of their historical demand for PRP-OMP vaccine.

For health care professionals who need to use the PRP-T vaccine to complete a series that was started with PRP-OMP (either PedvaxHIB or COMVAX (PRP-OMP/hepatitis B]), the following guidelines may be helpful:

Consult the Recommended Child and Adolescent Immunization Catch-up Schedule 2007 (1-page PDF; About PDFs) for the timing of doses for infants who start late or who are more than one month behind in their immunization series.

Vaccine availability updates will be provided as further information becomes available. Current information on vaccine supply issues is available on the CDC Web site.