Even with vaccine shortage, Hib rates not rising

Pediatricians and public health officials need to be sure that complete serotype data on patients infected with Haemophilus influenzae are available and reported in this era of deferred booster vaccinations, according to a speaker at the 43rd National Immunization Conference, held in Dallas this week.

Lt. Michael L. Jackson, PhD, MPH, of the National Center for Immunization and Respiratory Diseases Department at CDC, reported on the H. influenzae type b rates since the CDC recommended deferral of the booster dose in December of 2007. The CDC took this action when officials at Merck recalled the company’s vaccine due to manufacturing complications. A few months later, Merck officials noted a change in the company’s production processes, which also extended the vaccine shortages in the vaccine supply.

There has not been a resurgence in the rate of invasive Hib since the shortage, according to data compiled by Jackson and colleagues from the National Notifiable Diseases Surveillance System and the Active Bacterial Core surveillance system.

Jackson and colleagues noted 763 cases of H. influenzae among children younger than age 5. Of those, 6.4% were serotype B. However, Jackson said that 19 of 49 jurisdictions reporting H. influenzae cases were missing serotype data on more than half of their cases, and seven were missing serotype data for all cases.

He said this data is key in light of the vaccine shortage, as CDC officials plan to continue monitoring trends in HIB cases as the shortages are resolved. – by Colleen Zacharyczuk

For more information:

Jackson ML. #71. Presented at: National Immunization Conference. March 30-April 2, 2009; Dallas.

The widespread introduction of the polysaccharide conjugate Hib vaccine in the early 90s resulted in a 99% reduction of H. influenzae type b incidence. Most cases were still detected among unvaccinated or incompletely immunized children.

Merck's spontaneous recall of certain lots of its PRP-OMP conjugated Hib vaccines (PedvaxHIB and Comvax) last November created a dramatic shortage that prompted the CDC, in consultation with the ACIP, the AAFP and the AAP, to recommend deferral of the booster dose - regularly administered at 12 to 15 months - in immunocompetent children.

Two different outbreaks (Minnesota and Pennsylvania) demand our close attention for (1) eliciting immunization history, (2) performing early Hib detection and (3) ensuring adequate immunization according to the guidelines in place.

It is important to remember that the primary series offer a clinical efficacy greater or equal to 95%, and that children should receive their first dose at 2 months or as early as 6 weeks of age.

Invasive H. influenzae type b is a reportable condition. Serotyping H. influenzae isolates obtained from sterile sites (blood, CSF, osteoarticular fluid or tissue, etc.) should be routinely done to document population-based vaccine efficacy and to determine need for antimicrobial prophylaxis.

A latex agglutination test that detects capsular polysaccharide antigen is available for CSF specimen testing, although a negative result does not exclude the presence of the organism. Physicians should consult with their local city, state or reference laboratories to serotype specimens. The role of the infectious diseases specialist in providing these recommendations or in working in collaboration with his or her local and state resources cannot be emphasized enough.

– Federico Laham, MD

PediatricSupersite.com blogger