Second Disease Outbreak Illustrates Heightened Need to Complete Hib Primary Series

The AAFP has issued a statement agreeing with recommendations laid out in a CDC health advisory disseminated in the wake of an ongoing nationwide shortage of Haemophilus influenzae type b, or Hib, vaccine. In its statement, the Academy advises members who are having difficulty obtaining an adequate supply of Hib-containing vaccine to contact their vaccine suppliers and, if necessary, their state health departments.

The March 18 CDC advisory comes on the heels of two Hib disease outbreaks, the most recent of which was the focus of a health advisory issued on March 13 by the Pennsylvania Department of Health.

During the past six months, Pennsylvania has had four confirmed cases of Hib invasive disease in unvaccinated or incompletely vaccinated children younger than age 5 years. Three other cases of Haemophilus influenzae invasive disease in unvaccinated children under age 5 have not been serotyped, the state health department said.

Three of the seven children have died.

In January, Minnesota Department of Health officials said that five cases of invasive Hib disease in children younger than 5 were reported in that state last year. Three of the five children were completely unvaccinated against the disease. One child died.

The nationwide Hib vaccine shortage started when Merck & Co. Inc. recalled and later suspended production of some of its Hib-containing vaccine products in mid-December 2007. In response, the CDC, the AAFP and the American Academy of Pediatrics recommended temporarily deferring the Hib booster dose in healthy children not at high risk for invasive Hib disease.

In the interim, manufacturer sanofi pasteur has sought to fill the Hib vaccine gap with its monovalent vaccine, ActHIB, and another combination product.

However, CDC officials said in the March 18 health advisory that some clinicians may be experiencing "challenges" associated with switching from Merck's Hib vaccine to sanofi pasteur's product. Specifically, vaccine providers may be confused by the fact that sanofi pasteur's ActHIB primary series consists of three doses -- given at 2, 4 and 6 months of age -- whereas Merck's monovalent Hib product, PedvaxHIB, requires only two doses -- given at ages 2 and 4 months -- to complete the primary series.

Other challenges for providers, according to the CDC, include dealing with parents concerned about switching vaccine products and determining a catch-up schedule for children in whom the booster Hib dose has been deferred.

Because Merck is not expected to resume distribution of PedvaxHIB until later this year and delaying the primary Hib series poses a health risk, CDC officials are redoubling their efforts to inform and educate clinicians about other Hib vaccine options.

The CDC has stressed that if sanofi pasteur's combined diphtheria, tetanus toxoids, acellular pertussis, Hib and poliovirus vaccine, which is marketed as Pentacel, is the only Hib-containing vaccine available, the combination product should be used to complete the primary Hib series, even if doing so results in a child receiving additional doses of other antigens.

It is "more important than ever" to ensure children are protected from Hib disease because of falling immunization rates, according to the CDC advisory. Registries in some states show that coverage with the third Hib dose in the primary series is as much as 10 percent lower than that for other vaccines typically administered during the same visit.