Summary of Safety Assessment of Recalled Haemophilus influenzae type b (Hib) Conjugate Vaccines

A CDC report on findings from safety assessment after a voluntary recall of 1.2 million doses of Haemophilus influenzae type b (Hib) vaccines for concerns regarding potential Bacillus cereus (B. cereus) contamination is now available in Pharmacoepidemiology and Drug Safety. The report, Summary of Safety Assessment of Recalled Haemophilus influenzae type be (Hib) conjugate vaccines--United States, 2007-2008, was a collaborative effort involving the Food and Drug Administration (FDA) and CDC vaccine and laboratory experts.

On December 13, 2007 Merck & Company, Inc. voluntarily recalled 1.2 million doses of Haemophilus influenzae type b (Hib) vaccines that had been distributed since April 2007 for concerns regarding potential B cereus infections. In response to concerns about potential contamination, the Vaccine Adverse Event Reporting System (VAERS) and the Epidemic Information Exchange (Epi-X) were used to rapidly conduct post-recall safety surveillance for vaccine associated B cereus infections.

Hib vaccine is routinely recommended for children ages 2-59 months to prevent invasive Hib disease. Although precautionary, the recall disrupted the Hib vaccine supply in the U.S. from April 2007 to February 2008.

Based on a review of reports to VAERS and Epi-X, this assessment found no evidence of B. cereus infection in recipients of recalled Hib vaccines.

The report's main findings include the following:

No evidence of B. cereus infection was found in recipients of recalled Hib vaccines.

Routine testing identified B. cereus in the vaccine manufacturing process equipment, but not in individual vaccine lots.

B. cereus is commonly known as an agent of food poisoning, and can rarely cause serious non-gastrointestitinal infections in persons with compromised immune systems resulting in sepsis, endocarditis, meningitis, pneumonia, osteomeylitis, or wound infections.

VAERS received 75 reports involving recalled Hib vaccines from April 2007 through February 2008. A search of the VAERS database for "Bacillus" or "cereus" was also performed to identify potential reports of infection. The reports were analyzed by seriousness and adverse event patterns. There were 5 reports of death. Before the recall, no B. cereus infection that occurred after vaccination had been reported to VAERS.

A CDC medical officer reviewed medical records of all serious reports involving recalled Hib vaccines. For each death report, autopsy results, in conjunction with state health departments, local medical examiners, and CDC's Infectious Disease Pathology Branch, sought evidence of B. cereus infections. Tissue specimens were obtained for 4 or the 5 deaths; none of these specimens revealed evidence of B. cereus infection.

In December 2007, CDC's Epi-X was used to collect information from among thousands of public health professionals and infectious disease specialists for vaccine-associated B. cereus infection. One report of vaccine-associated B. cereus infection was found in a child who received a non-recalled Hib vaccine from the same manufacturer. The patient's B. cereus isolate did not have the same genotype ("fingerprints") as the B. cereus isolated from the manufacturing equipment.