The Alaska Haemophilus influenzae type b experience: lessons in controlling a vaccine-preventable disease

OBJECTIVE

Before 1991, Alaska Native children experienced one of the highest rates of invasive Haemophilus influenzae type b disease. H influenzae type b vaccine has led to a near-elimination of invasive H influenzae type b disease in the United States. We describe challenges encountered in controlling H influenzae type b disease in Alaska and update the current status of H influenzae disease and carriage in Alaska as lessons to other populations.

PATIENTS AND METHODS

We reviewed data from statewide H influenzae disease surveillance conducted during 1980-2004. Vaccine coverage data were based on audits from tribal facilities and the National Immunization Survey. H influenzae type b colonization data were based on 6 carriage studies.

RESULTS

After universal infant vaccination in 1991, H influenzae type b disease among Alaska Native and non-Native children < 5 years of age decreased by 94% and 96%, respectively. After a 1996 change in H influenzae type b vaccine from polyribosylribitol phosphate-outer membrane protein conjugate vaccine to H influenzae type b oligosaccharide-CRM197 vaccine, the incidence of H influenzae type b disease increased in rural Alaska Natives from 19.8 to 91.1 cases per 100000 per year < 5 years of age. During 2001-2004, with use of polyribosylribitol phosphate-outer membrane protein conjugate vaccine, the rate of H influenzae type b disease in Alaska Native and non-Native children aged < 5 years decreased to 5.4 and 0 per 100000 per year, respectively. In postvaccine studies, H influenzae type b carriage has decreased in Alaska Native children < 5 years of age.

CONCLUSIONS

H influenzae type b vaccination has resulted in a dramatic decrease in invasive H influenzae type b disease in Alaska; however, despite high rates of H influenzae type b vaccine coverage, H influenzae type b disease rates among rural Alaska Native children < 5 years of age remain higher than the rates among non-Native Alaska and other US children. Equity in disease rates may not be achieved in indigenous populations with the current vaccines unless other environmental and household factors contributing to disease transmission are addressed.

Severe chronic neutropenia: treatment and follow-up of patients in the Severe Chronic Neutropenia International Registry

Severe chronic neutropenia (SCN) is defined as an absolute neutrophil (ANC) of less than 0.5 x 10(9)/L, lasting for months or years. Congenital, cyclic, and idiopathic neutropenia are principal categories of SCN. Since 1994, the Severe Chronic Neutropenia International Registry (SCNIR) has collected data to monitor the clinical course, treatments, and disease outcomes for SCN patients. This report summarizes data for 853 patients, almost all treated with daily or alternate-day recombinant human granulocyte colony-stimulating factor (G-CSF or Filgrastim). G-CSF treatment increased the ANC overall from 0.34 x 10(9)/L +/- 0.018 pre-treatment to 3.70 x 10(9)/L +/- 0.18 during the first year of treatment. For most patients, the responses were durable with patients remaining on the same dose of G-CSF for many years. Long-term hematological observations showed stable mean leukocyte and neutrophil counts and gradually increasing hemoglobin levels. Thrombocytopenia developed in 4% of patients. As of January 1, 2000, myelodysplasia (MDS) or acute myelogenous leukemia (AML) has occurred in 35 of 387 patients with congenital neutropenia with a cumulative risk of 13% after 8 years of G-CSF treatment. This event occurred without a predictable relationship to the duration or dose of G-CSF treatment. No patients with cyclic or idiopathic neutropenia developed MDS or AML. Other important adverse events included hepatomegaly, osteoporosis, vasculitis, glomerulonephritis, and deaths in 4 of 14 cases requiring splenectomy. Growth and development and the outcome of pregnancy appeared to be unaffected by G-CSF treatment. These data indicate that congenital, cyclic, and idiopathic neutropenia can be effectively treated with long-term G-CSF. The risk of leukemia, osteoporosis, other potentially adverse events, and pregnancy outcome need to be further evaluated with continuing long-term observations.

Risk and benefit of treatment of severe chronic neutropenia with granulocyte colony-stimulating factor

The Severe Chronic Neutropenia International Registry (SCNIR) was established in 1994 following four phase I/II and one phase III clinical trial on the use of filgrastim (recombinant human granulocyte colony-stimulating factor [r-metHuG-CSF]) as a treatment for severe chronic neutropenia (SCN). A primary purpose of the SCNIR is to monitor SCN patients treated with filgrastim for adverse events that might occur over time. As of December 31, 2000, 832 patients with SCN (384 congenital, 160 cyclic, 288 idiopathic) were enrolled. Clinical trial and Registry data show that filgrastim is an effective treatment for SCN; more than 90% of patients treated respond with normalization of blood neutrophil counts. The SCNIR has collected data on bone pain, splenomegaly, hepatomegaly, thrombocytopenia, osteopenia/osteoporosis, vasculitis, glomerulonephritis, growth and development, pregnancy and fertility, leukemic transformation, and mortality. Analysis of data from patients who received filgrastim for up to 11 years did not identify any adverse events associated with increased duration of treatment.