CDC Urging Docs to Complete Hib Primary Series

With the nation's shortage of Haemophilus influenzae type b, or Hib, vaccine now stretching into its 15th month, the CDC is directly contacting thousands of health care providers with a reminder that all children should complete the primary Hib immunization series.

The CDC is including this message in a letter dated Feb. 10 (2-page PDF; About PDFs) that will accompany all vaccine shipments to providers who participate in its Vaccines for Children, or VFC, program.

Slightly less than half of AAFP members are VFC participants, according to the results of the Academy's 2008 Immunization Survey. In a recent conference call with immunization stakeholder groups, however, CDC officials made it clear that all clinicians who provide childhood immunizations should heed the message.

The nationwide Hib vaccine shortage started when Merck & Co. Inc. recalled multiple lots of two of the company's products that contain Hib conjugate vaccine in mid-December 2007. Merck ceased production of those vaccines because of potential product contamination and has not yet resumed distribution.

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

"Our goal is to be able to ramp up supply to allow the U.S. to return to the full Hib immunization series, including the booster dose, by the summer of 2009, even if Merck does not return to the market as anticipated," sanofi pasteur said in a January 2009 letter to providers (2-page PDF; About PDFs) posted on its Web site. "We will continue to work closely with the CDC to review plans to achieve this goal."

Shortly after Merck announced its recall in 2007, the CDC, in consultation with its Advisory Committee on Immunization Practices, the AAFP and the American Academy of Pediatrics, recommended that health care professionals defer the Hib booster dose typically given at age 12-15 months, except for children in certain high-risk groups.

The Hib vaccine supply problems and the recommended booster deferral may have resulted in "higher Hib carriage in nonsymptomatic children, increased cases and at least one death," CDC officials noted in the Feb. 10 letter.

That reference was to an article in the Jan. 23 Morbidity and Mortality Weekly Report, in which the CDC described five cases of invasive Hib disease in children younger than age 5 years that were reported last year to the Minnesota Department of Health. Three of the five children were completely unvaccinated against the disease. One child died.

The agency said in its recent letter that sufficient vaccine is available to enable all infants to complete the primary series. However, public health officials have said that different dosing schedules for Merck's products and those of sanofi pasteur may have caused confusion and led to lower vaccination rates in Minnesota.

Sanofi pasteur's ActHIB primary series consists of three doses, given at 2, 4 and 6 months of age; Merck's monovalent Hib product, PedvaxHIB, requires only two doses to complete the primary series, typically given at ages 2 and 4 months.

The CDC also noted in its Feb. 10 letter 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 it results in a child receiving additional doses of other antigens.

"The Hib-containing vaccine products that are available may not be what you are used to using in your practice," the agency said in the letter. "However, the potential increased bacterial carriage in any area makes it more important than ever that children are adequately protected."

The CDC provided the following schedules for children who are not at increased risk for invasive Hib disease:

Meanwhile, children at increased risk for Hib disease should receive the full series of Hib vaccine, including the booster dose. This includes children with asplenia, sickle cell disease, HIV infection and certain other immunodeficiency syndromes and malignant neoplasms, as well as American Indian and Alaska Native children.