Hib Vaccine Shortage Leads to Heightened Disease Surveillance

The CDC is stepping up its surveillance for Haemophilus influenzae type b, or Hib, disease in the wake of a continued shortage of Hib conjugate vaccine. Accordingly, the agency is asking physicians to contact their local health departments when invasive H. influenzae disease is suspected.

The CDC said in its Nov. 21 Morbidity and Mortality Weekly Report, or MMWR, that it had reviewed 4,657 cases of invasive H. influenzae infection reported from January 2007 to October 2008, including 748 cases among children younger than age 5 years. Of those 748 cases, 6 percent were found to have been caused by Hib; 37.2 percent were missing serotype information.

"The continued vaccine shortage heightens the need for timely reporting and investigation of H. influenzae cases and accurate serotyping of all invasive H. influenzae isolates in children" younger than 5, the agency said.

In December 2007, Merck & Co. Inc. announced a voluntary recall involving two of the company's vaccine products containing Hib conjugate vaccine. Merck suspended production of both vaccines because of concerns about potential product contamination. At that time, the manufacturer estimated that distribution would resume in the fourth quarter of 2008, but Merck announced in October of this year that distribution would be delayed until mid-2009.

Shortly after Merck announced its recall, the CDC, in consultation with its Advisory Committee on Immunization Practices, the AAFP and the American Academy of Pediatrics, recommended that health care providers defer the Hib booster dose -- normally given at age 12-15 months -- except for children in high-risk groups, such as those with asplenia, sickle cell disease, or HIV infection and certain other immunodeficiency syndromes, as well as children who have malignant neoplasms.

In addition, American Indian and Alaska Native children, who are at increased risk for invasive Hib disease, still should receive the booster dose, according to the CDC's interim recommendations.

According to the Nov. 21 MMWR report, sufficient vaccine exists in the United States to continue providing the primary series and booster dose for children in the at-risk groups through at least mid-2009. However, the agency said that in light of the ongoing delay in returning the vaccines to market, its interim recommendations regarding Hib booster doses should remain in place.

"What effect continued deferral of the Hib booster might have on the incidence of invasive Hib disease in young children in the United States is unknown," the MMWR report noted. Although the CDC's analysis has detected no increase in the incidence of invasive Hib disease in young children since the 2007 recall, said the report, other factors suggest that "prolonged deferral of the Hib booster dose might yet lead to changes in the epidemiology of Hib disease in the United States."

The CDC offers an online listing of state health department Web sites, many of which provide contact information for local health departments. CDC officials plan to continue to solicit serotype information on reported cases of invasive HIB disease from state health departments, and they urge health departments and state and hospital laboratories to step up their "timely serotyping and reporting" efforts.