Healthcare Infection Prevention

Hib vaccine lots recalled, production stopped

CDC: Shortage predicted

Recall of a dozen lots of two Haemophilus influenzae type b (Hib) vaccines and suspension of production by a major manufacturer will result in a national shortage that could put children at risk and will certainly trouble physicians and parents in the short run, Julie Gerberding, MD, MPH, director of the Centers for Disease Control and Prevention, warns.

"This is not an immediate health threat, but we do need to do everything we can to restore effective vaccine coverage in the long run because children are at risk for [HIB] disease if we don't solve this problem over the next several months," she said at a recent press conference. "We anticipate that the short-term shortages are going to be very inconvenient and very messy to sort out."

The recall affects about 1 million of the 14 million doses annually distributed in the United States. Though downplaying any immediate risk, Gerberding emphasized that the shortage hits a very important vaccine. "It helps protect children from meningitis, from pneumonia, from severe throat infections and other serious blood stream infections caused by Hib," she said. "Before this vaccine was licensed and used, we experienced about 20,000 cases of HIB disease in the United States, and about 1,000 children died every year from this infection. But thanks to these vaccines that have been around for the last decade or so, there are fewer than 100 documented cases of HIB disease in the entire United States each year, a reduction of more than 99%. So obviously, this is an extremely effective vaccine that has saved the lives of many, many children."

The recommended vaccination schedule for Hib vaccine is a primary series (consisting of two or three doses, depending on the formulation) administered beginning at two months and a booster dose at age 12-15 months. Because of the short-term reduction in available doses of Hib-containing vaccines, CDC recommends that providers temporarily stop the routine Hib vaccine booster dose except to children in high-risk groups.1 Providers should register and track children for whom the booster dose is deferred in order to recall them for vaccination when supply improves. The action is not likely to result in an increased risk for Hib disease because of continued protection of children with the primary series and the low level of carriage and transmission currently in the United States, the CDC noted.

Children considered at high risk for Hib disease include those with asplenia, sickle cell disease, malignant neoplasms, HIV and other immunodeficiency syndromes. The CDC recommends that providers continue to vaccinate these children with available Hib conjugate vaccines according to the routinely recommended schedules, including the 12-15 month booster dose. American Indian/Alaska Native (AI/AN) children also are at increased risk for Hib disease, particularly in the first six months of life. Before the use of Hib conjugate vaccines, the incidence of Hib disease among young AI/AN children in AI/AN communities was approximately 10 times higher than among children of comparable age in the general population.

"I think the most important priority group in this country is Alaska Native/American Indian children," Anne Schuchat, MD, director of the CDC's national center for immunization and respiratory diseases, said at the press conference. "They have much higher rates of Hib disease than others do. They have been a special population for Hib from the beginning. In fact, many of the vaccine studies were done in that population. It's also a fairly small group of children. I think we've already made the decision that we've prioritized our stockpile vaccine for the American Indian/Alaska Native children."

Bacillus cereus found on equipment

On Dec. 13, 2007, Merck & Co. in West Point, PA, announced a voluntary recall of certain lots of two Haemophilus influenzae type b (Hib) conjugate vaccines, PedvaxHIB® (monovalent Hib vaccine) and Comvax® (Hib/hepatitis B vaccine). Providers are being asked to return unused vaccine from these recalled lots using procedures outlined on the Merck web site (www.merckvaccines.com/PCHRecall.pdf).

Merck, which produces roughly half of the Hib conjugate vaccines used in the United States, has suspended production of the vaccine and does not expect to resume distribution until the fourth quarter of 2008, the CDC reports. Merck took the steps as a precautionary measure because potential contamination in the specific lots was identified as part of the company's standard evaluation of its manufacturing processes. In routine testing of the vaccine manufacturing equipment used to produce the vaccines, the company found Bacillus cereus, a gram-positive enteric pathogen typically associated with food poisoning. Sterility tests of the vaccine lots themselves have not found any contamination. No adverse reactions in vaccinated children had been reported as this issue went to press, but parents of children recently vaccinated with recalled vaccine should watch for any signs of infection (such as redness and swelling at the injection site) and contact their providers if such reactions occur. Vaccine potency was not affected, so children who were immunized with the affected vaccines do not need to be revaccinated.

Two other shots available

Two other Hib conjugate vaccines manufactured by Sanofi Pasteur (Swiftwater, PA) are currently licensed and available for use in the United States. However, Sanofi Pasteur likely will not be able to immediately provide adequate Hib vaccine to vaccinate fully all children for whom the vaccine is recommended. The CDC is working with manufacturers to address the issue and expects to draw from its own emergency stockpile of Hib vaccine as the shortage unfolds. "We know that a portion of our stockpile will also be affected by this recall, so the flexibility and future ability to backfill for shortages and so forth has been lost by this change," Gerberding said.

Fortunately, current immunization rates in the United States for Hib vaccine are high. In 2006, about 94% of U.S. children 19-35 months of age were vaccinated against Hib. "We have very low disease rates and very low carriage rates in our population, so we would not expect any meningitis outbreaks for many months because our population is so highly immune," she said. At the same time, the CDC is taking the situation very seriously because experience has shown that when immunization rates fall affected populations are susceptible to increases in disease occurrence. "CDC will be continuing our close surveillance for Haemophilus disease in children, and we will be heightening our attention in some of our special programs that we use to give a sentinel look at invasive disease," she added.

[Editor's note: Any adverse events that are potentially vaccine-related should be reported to the Vaccine Adverse Event Reporting System (VAERS) at (800) 822-7967 or online at http://www.vaers.hhs.gov.]

Reference

  1. Centers for Disease Control and Prevention. Interim Recommendations for the Use of Haemophilus influenzae Type b (Hib) Conjugate Vaccines Related to the Recall of Certain Lots of Hib-Containing Vaccines (PedvaxHIB® and Comvax®) MMWR 2007; 56(Dispatch):1-2.