Infectious Diseases: October 30, 2004
Infectious Diseases: October 30, 2004
Centers for Disease Control and Prevention (CDC). Fact sheet. 2004-05 Flu vaccine shortage: who should get vaccinated. October 15, 2004. British authorities have suspended the license of Chiron to produce the influenza vaccine. This was the anticipated source of 46-48 million doses for the United States -- nearly half of this nation's supply. The result is the need to prioritize the available supply from other sources. The following groups should be vaccinated:
Healthy persons aged 2-64 years should not be vaccinated or should wait until those who have a high priority have been vaccinated.
Thompson WW, Shay DK, Weintraub E, et al. Influenza-associated hospitalizations in the United States. JAMA. 2004;292:1333-1340. The goal was to estimate the annual influenza-associated hospitalizations in the United States and to identify age associations. The study authors used the National Hospital Discharge Summary for hospitalization data and World Health Organization (WHO) laboratories for influenza surveillance data. The analysis was for the 1979-1980 through the 2000-2001 seasons on the basis of 270,000 inpatient records from approximately 500 hospitals representing 1% of all inpatients in the United States. The International Classification of Diseases, Ninth Revision (ICD-9) codes were examined for pneumonia and hospitalizations. The laboratory surveillance data showed that an average of 30,936 specimens were submitted for influenza testing and 13.3% were positive. The predominant strains (based on those that accounted for 20% or more) were influenza A (H1N1) in 7 years, influenza A (H3N2) in 15 years, and influenza B in 11 years. The hospital analysis showed that pneumonia and influenza represented 12.4% of those categorized as primary respiratory and circulatory hospitalizations. The average number with an ICD-9 code indicating influenza or pneumonia was an average of 1,097,564. There was a gradual increase in the number of hospitalizations from 866,000 in 1979-1980 to 1,325,000 in 2000-2001. These data are summarized in Table 1 , which indicates the year, the predominant strain, and the number hospitalized with a diagnosis of influenza or pneumonia during the influenza season.
The study authors also noted that, not surprisingly, the rate of hospitalization was substantially greater during seasons in which influenza A (H3N2) predominated ( Table 2 ). The major factor associated with the increase in rates of hospitalization was the increase in the elderly, although rates stratified by person-years significantly changed. These data are summarized in Table 3 , which is restricted to the rates of hospitalization in which pneumonia or influenza was listed as a primary diagnosis.
The investigators conclude that there has been a substantial increase in the number of hospitalizations associated with influenza, and most of this increase is a reflection of the aging population. Also of note are the rates associated with children under 5 years of age, thus emphasizing the age extremes as the group at particular risk.
Comment: The study authors summarize an enormous amount of data dealing with influenza-related morbidity with the conclusion that the highest priority should be influenza-prevention efforts in the young and the old. The concern for children was brought into focus with the report of 152 deaths attributed to influenza in the 2003-2004 season. The investigators suggest that, beyond vaccination, there needs to be consideration of other prevention strategies for the "elderly, elderly" due to decreased immune responsiveness associated with aging.
Kiso M, Mitamura K, Sakai-Tagawa Y, et al. Resistant influenza A viruses in children treated with oseltamivir: descriptive study. Lancet. 2004;364:759-765. The study authors obtained influenza virus from patients with influenza who had been treated with oseltamivir and sequenced the genes for neuraminidase and hemagglutinin for mutations conferring resistance to oseltamivir. Among 50 isolates, there were 9 (18%) with neuraminidase mutations associated with resistance. These strains were detected on day 4 of treatment and subsequently were shed for at least 3 additional days. The investigators conclude that oseltamivir-resistant mutants in children are more common than generally suspected.
Comment: This is a disappointing report given our hopes for oseltamivir in the event of pandemic influenza, including the Asian strain, which now appears sensitive to this agent. The prior reports of resistance have been sparse, with an impression that resistance is unusual for the neuraminidase inhibitors because it is relatively difficult to produce in vitro. This report suggests that it should be a greater concern. With respect to Asian influenza (H5N1), resistance has been reported to amantadine and rimantadine, but not to the neuraminidase inhibitors -- at least not yet.
Centers for Disease Control and Prevention (CDC). Fact sheet. 2004-05 Flu vaccine shortage: who should get vaccinated. October 15, 2004. British authorities have suspended the license of Chiron to produce the influenza vaccine. This was the anticipated source of 46-48 million doses for the United States -- nearly half of this nation's supply. The result is the need to prioritize the available supply from other sources. The following groups should be vaccinated:
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Healthy persons aged 2-64 years should not be vaccinated or should wait until those who have a high priority have been vaccinated.
Thompson WW, Shay DK, Weintraub E, et al. Influenza-associated hospitalizations in the United States. JAMA. 2004;292:1333-1340. The goal was to estimate the annual influenza-associated hospitalizations in the United States and to identify age associations. The study authors used the National Hospital Discharge Summary for hospitalization data and World Health Organization (WHO) laboratories for influenza surveillance data. The analysis was for the 1979-1980 through the 2000-2001 seasons on the basis of 270,000 inpatient records from approximately 500 hospitals representing 1% of all inpatients in the United States. The International Classification of Diseases, Ninth Revision (ICD-9) codes were examined for pneumonia and hospitalizations. The laboratory surveillance data showed that an average of 30,936 specimens were submitted for influenza testing and 13.3% were positive. The predominant strains (based on those that accounted for 20% or more) were influenza A (H1N1) in 7 years, influenza A (H3N2) in 15 years, and influenza B in 11 years. The hospital analysis showed that pneumonia and influenza represented 12.4% of those categorized as primary respiratory and circulatory hospitalizations. The average number with an ICD-9 code indicating influenza or pneumonia was an average of 1,097,564. There was a gradual increase in the number of hospitalizations from 866,000 in 1979-1980 to 1,325,000 in 2000-2001. These data are summarized in Table 1 , which indicates the year, the predominant strain, and the number hospitalized with a diagnosis of influenza or pneumonia during the influenza season.
The study authors also noted that, not surprisingly, the rate of hospitalization was substantially greater during seasons in which influenza A (H3N2) predominated ( Table 2 ). The major factor associated with the increase in rates of hospitalization was the increase in the elderly, although rates stratified by person-years significantly changed. These data are summarized in Table 3 , which is restricted to the rates of hospitalization in which pneumonia or influenza was listed as a primary diagnosis.
The investigators conclude that there has been a substantial increase in the number of hospitalizations associated with influenza, and most of this increase is a reflection of the aging population. Also of note are the rates associated with children under 5 years of age, thus emphasizing the age extremes as the group at particular risk.
Comment: The study authors summarize an enormous amount of data dealing with influenza-related morbidity with the conclusion that the highest priority should be influenza-prevention efforts in the young and the old. The concern for children was brought into focus with the report of 152 deaths attributed to influenza in the 2003-2004 season. The investigators suggest that, beyond vaccination, there needs to be consideration of other prevention strategies for the "elderly, elderly" due to decreased immune responsiveness associated with aging.
Kiso M, Mitamura K, Sakai-Tagawa Y, et al. Resistant influenza A viruses in children treated with oseltamivir: descriptive study. Lancet. 2004;364:759-765. The study authors obtained influenza virus from patients with influenza who had been treated with oseltamivir and sequenced the genes for neuraminidase and hemagglutinin for mutations conferring resistance to oseltamivir. Among 50 isolates, there were 9 (18%) with neuraminidase mutations associated with resistance. These strains were detected on day 4 of treatment and subsequently were shed for at least 3 additional days. The investigators conclude that oseltamivir-resistant mutants in children are more common than generally suspected.
Comment: This is a disappointing report given our hopes for oseltamivir in the event of pandemic influenza, including the Asian strain, which now appears sensitive to this agent. The prior reports of resistance have been sparse, with an impression that resistance is unusual for the neuraminidase inhibitors because it is relatively difficult to produce in vitro. This report suggests that it should be a greater concern. With respect to Asian influenza (H5N1), resistance has been reported to amantadine and rimantadine, but not to the neuraminidase inhibitors -- at least not yet.
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