Merck Recalls 1 Million Hib Vaccine Doses

Vaccine manufacturer Merck & Co. Inc. yesterday announced a voluntary recall involving two vaccine products containing its Haemophilus influenzae type b, or Hib, conjugate vaccine because of a potential for contamination of these products. The recall covers 10 lots of Merck's Hib conjugate vaccine, sold as PedvaxHIB, and two lots of its combination Hib/hepatitis B vaccine, COMVAX. In all, about 1 million doses of vaccine have been recalled.

No adverse events associated with use of the affected vaccine products have been reported, and CDC officials have said that the situation, while not representing a true "health threat," certainly represents a "major inconvenience" for health care professionals, who are advised to not administer vaccine from the affected lots.

Details about the specific lots being recalled and instructions for returning unused vaccine were included in a letter Merck sent (3-page Word file; About Downloading) yesterday to its vaccine customers; that information also is available on the CDC's Current Vaccine Shortages and Delays Web page.

Merck said it issued the recall after routine testing of equipment used to manufacture the vaccine identified the presence of Bacillus cereus, a pathogen that can cause gastrointestinal symptoms, including abdominal pain, nausea, vomiting and diarrhea.

Subsequent testing of the affected lots found no contamination of the vaccine doses themselves.

Pedvax is indicated for routine immunization of infants and children against invasive Hib disease. COMVAX is indicated for immunization of infants and children against invasive Hib disease, as well as against infection caused by all known subtypes of hepatitis B virus in infants born to hepatitis B surface antigen-negative mothers. Current immunization recommendations call for administration of one dose of either of these vaccines at age 2 months and again at age 4 months, with a booster dose at 12-15 months.

In a Dec. 12 news conference about the recall, CDC Director Julie Gerberding, M.D., noted that children who already have received vaccine from the affected lots do not need to be revaccinated because the potency of the vaccine has not been diminished. In addition, she said, because the CDC estimates that overall Hib vaccine coverage is approximately 92 percent, there is no immediate cause for concern about invasive Hib disease, including meningitis.

However, she added, because Merck supplies about 50 percent of the nation's Hib vaccine -- including about one-half of the vaccine included in the CDC's vaccine stockpile -- the current situation portends a shortage of unknown duration. Accordingly, it is expected that interim recommendations regarding Hib immunization will be developed and disseminated within the next few days.

Of particular concern, Gerberding noted, would be the immunization status of immunocompromised children, as well as that of American Indian and Alaska Native children, all of whom are at increased risk for complications from Hib disease. Gerberding said she anticipated that the lion's share of the CDC stockpile would go to ensuring appropriate coverage in these populations.

According to Jonathan Temte, M.D., Ph.D., of Madison, Wis., one of the Academy's two liaisons to the CDC's Advisory Committee on Immunization Practices, or ACIP, the issue has been on a "very fast track" since it first came to light. For that reason, he said, interim recommendations may well be handled at a CDC staff level, with input from stakeholders, such as the AAFP, rather than via the formal ACIP process.

Temte said that what he sees as most likely to happen is that the CDC would issue a temporary call to forgo the booster dose in children who have received the primary series and who are not at increased risk for invasive Hib disease. "You want to protect the very youngest kids and the kids at high risk," said Temte, adding that "you get the most bang from the first two doses."

In November, Merck announced that it was "temporarily unable to ship" Pedvax, although the company said at that point it had sufficient supplies of COMVAX to "meet historical demand" for that vaccine.

At that time, a contingency plan was being implemented by the CDC, Merck and sanofi pasteur, the U.S. market's only other supplier of Hib vaccine. That plan called for sanofi pasteur to boost production of its own Hib conjugate vaccine, ActHIB. Unlike Pedvax and COMVAX, both of which are each conjugated to a meningococcal outer membrane protein, ActHIB is conjugated to a tetanus toxoid.

To view the current Recommended Childhood Immunization Schedule, visit the AAFP Immunization Resources Web page. Physicians and other health care professionals are encouraged to report any adverse events associated with vaccine administration to the joint CDC-FDA Vaccine Adverse Event Reporting System, or VAERS. Reports to VAERS can be made online or by calling (800) 822-7967.