mlk_man
05-17-2005, 01:22 PM
From Medscape Infectious Diseases (http://www.medscape.com/infectiousdiseaseshome)http://images.medscape.com/pi/global/ornaments/spacer.gif
Expert Reviews and Commentary (http://www.medscape.com/px/viewindex/more?Bucket=columns&SectionId=1867)
Infectious Diseases: May 15, 2005
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John Bartlett, MD
Influenza
Hak E, Buskens E, van Essen GA, et al. Clinical effectiveness of influenza vaccination in persons younger than 65 years with high-risk medical conditions: the PRISMA study. Arch Intern Med. 2005;165:274-280 (http://intapp.medscape.com/px/medlineapp/getdoc?pmi=15710789&cid=med) . The report is by the primary care-based Prevention of Influenza, Surveillance and Management (PRISMA) study from The Netherlands. The goal was to determine the benefits of influenza vaccine with particular emphasis on high-risk patients who are less than 65 years of age and for whom vaccine is recommended.
Methods: This was a case-controlled study conducted during the 1999-2000 influenza A epidemic based on observations with 75,227 primary care patients. The year selected for study was the year of a large epidemic attributed to influenza A (H3N2) Sydney. The target population studied was patients who fit the Dutch guidelines for influenza vaccine for persons < 65 years (which is essentially identical to recommendations in the United States). The study involved 91 practices with 75,227 patients. End points for the study were deaths, hospitalizations, and outpatient visits. Vaccine effectiveness was calculated on the basis of multivariant logistic regression modeling to determine the odds ratio.
Results: The results showed substantial benefit of influenza vaccine in terms of reduction in mortality, hospitalizations, and outpatient visits. The results are provided in Table 1 (http://www.medscape.com/viewarticle/503836_Tables#T1) according to 3 age categories: persons < 18 years, persons 18-64 years who are considered high-risk based on comorbidities, and persons > 65 years.
Conclusion: The study authors conclude that patients with high-risk medical conditions benefit substantially from annual influenza vaccine during an epidemic.
Comment: The study authors claim that this is the first study to demonstrate benefit of influenza vaccine in high-risk persons < 65 years. In the United States, this group accounts for approximately 50% of the total target population for influenza vaccine, although vaccination rates are below 40%.[1] With respect to outpatient visits, the results indicated a 43% reduction in general practice visits for influenza, pneumonia, exacerbations of chronic bronchitis, and acute otitis media. Among all persons over 18 years, there was a 55% reduction in deaths and hospitalizations, including significant reductions in rates of hospitalization for pneumonia or influenza (63%), myocardial infarction (48%), and stroke (71%). Others have also shown this decrease in cardiovascular and cerebrovascular complications attributed to influenza vaccine.[2-5] It should be emphasized that these conclusions apply to an influenza season associated with a particularly large epidemic. The PRISMA study was actually designed to analyze 3 seasons, but the 2000-2001 and 2001-2002 seasons have relatively low influenza activity and consequently were not included in the analysis.
Simonsen L, Reichert TA, Viboud C, Blackwelder WC, Taylor RJ, Miller MA. Impact of influenza vaccination on seasonal mortality in the US elderly population. Arch Intern Med. 2005;165:265-272 (http://intapp.medscape.com/px/medlineapp/getdoc?pmi=15710788&cid=med) . The study authors note that there are numerous observational studies to support the substantial benefits of influenza vaccination among elderly persons in the United States. They also note that clinical trials with vaccine have shown up to 60% efficacy in reducing culture-confirmed influenza illness in elderly persons.[6] Nevertheless, this and other trials have not examined mortality as an outcome. They note that in the United States, the emphasis on influenza vaccine among elderly persons has resulted in an increase in the number of elderly vaccinated from 15% to 20% before 1982 to 62% in 2002. Their study was designed to determine the influenza-related mortality for the past 3 decades with particular attention to adjusting for age and adjusting for seasons dominated by influenza A (H3N2), which dominated in the 1990s. Their study showed that excess all-cause mortality never exceeded 10% for the elderly during the winter months. With regard to influenza-related deaths, persons > 85 years accounted for 24% in the 1970s and for 44% in the 1990s. With regard to the 12 seasons in which influenza A (H3N2) was the dominant influenza strain, there was no evidence for any trend in all-cause mortality. Thus, their data for 33 seasons indicated that influenza-related mortality was always less than 10% of the total number of winter deaths among the elderly. Further, these observations applied to the 1968 pandemic and the severe 1997-1998 season in which there was a mismatch vaccine formulation. For persons aged 65-74 years, excess mortality in the A (H3N2)-predominant seasons fell from 1968 to the early 1980s, but stayed approximately the same thereafter. They conclude that access mortality for persons over 65 years never exceeded 10% in all winter deaths. Consequently, they did not believe that increasing vaccination rates after 1980 could be credited with a decline in mortality rates for any age group. They also conclude that observational studies substantially overestimate the benefits of the vaccine.
Comment: This study was reviewed by Jon Cohen for Science in "News of the Week" ( Science . 2005;307:1026). He notes that the study, not surprisingly, provoked wildly different reactions. Walter Orenstein, former head of the National Immunization Program for the US Centers for Disease Control and Prevention (CDC), concluded that it was a very important and troubling study. By contrast, William Thompson, from the CDC, believed that it was "extremely weak and overstates the results." The conclusion is that this review by Simonsen and associates raises issues about the current US flu vaccine policy and has now stimulated a "hot debate."
http://images.medscape.com/pi/global/ornaments/spacer.gif
Expert Reviews and Commentary (http://www.medscape.com/px/viewindex/more?Bucket=columns&SectionId=1867)
Infectious Diseases: May 15, 2005
http://images.medscape.com/pi/global/ornaments/spacer.gif
John Bartlett, MD
Influenza
Hak E, Buskens E, van Essen GA, et al. Clinical effectiveness of influenza vaccination in persons younger than 65 years with high-risk medical conditions: the PRISMA study. Arch Intern Med. 2005;165:274-280 (http://intapp.medscape.com/px/medlineapp/getdoc?pmi=15710789&cid=med) . The report is by the primary care-based Prevention of Influenza, Surveillance and Management (PRISMA) study from The Netherlands. The goal was to determine the benefits of influenza vaccine with particular emphasis on high-risk patients who are less than 65 years of age and for whom vaccine is recommended.
Methods: This was a case-controlled study conducted during the 1999-2000 influenza A epidemic based on observations with 75,227 primary care patients. The year selected for study was the year of a large epidemic attributed to influenza A (H3N2) Sydney. The target population studied was patients who fit the Dutch guidelines for influenza vaccine for persons < 65 years (which is essentially identical to recommendations in the United States). The study involved 91 practices with 75,227 patients. End points for the study were deaths, hospitalizations, and outpatient visits. Vaccine effectiveness was calculated on the basis of multivariant logistic regression modeling to determine the odds ratio.
Results: The results showed substantial benefit of influenza vaccine in terms of reduction in mortality, hospitalizations, and outpatient visits. The results are provided in Table 1 (http://www.medscape.com/viewarticle/503836_Tables#T1) according to 3 age categories: persons < 18 years, persons 18-64 years who are considered high-risk based on comorbidities, and persons > 65 years.
Conclusion: The study authors conclude that patients with high-risk medical conditions benefit substantially from annual influenza vaccine during an epidemic.
Comment: The study authors claim that this is the first study to demonstrate benefit of influenza vaccine in high-risk persons < 65 years. In the United States, this group accounts for approximately 50% of the total target population for influenza vaccine, although vaccination rates are below 40%.[1] With respect to outpatient visits, the results indicated a 43% reduction in general practice visits for influenza, pneumonia, exacerbations of chronic bronchitis, and acute otitis media. Among all persons over 18 years, there was a 55% reduction in deaths and hospitalizations, including significant reductions in rates of hospitalization for pneumonia or influenza (63%), myocardial infarction (48%), and stroke (71%). Others have also shown this decrease in cardiovascular and cerebrovascular complications attributed to influenza vaccine.[2-5] It should be emphasized that these conclusions apply to an influenza season associated with a particularly large epidemic. The PRISMA study was actually designed to analyze 3 seasons, but the 2000-2001 and 2001-2002 seasons have relatively low influenza activity and consequently were not included in the analysis.
Simonsen L, Reichert TA, Viboud C, Blackwelder WC, Taylor RJ, Miller MA. Impact of influenza vaccination on seasonal mortality in the US elderly population. Arch Intern Med. 2005;165:265-272 (http://intapp.medscape.com/px/medlineapp/getdoc?pmi=15710788&cid=med) . The study authors note that there are numerous observational studies to support the substantial benefits of influenza vaccination among elderly persons in the United States. They also note that clinical trials with vaccine have shown up to 60% efficacy in reducing culture-confirmed influenza illness in elderly persons.[6] Nevertheless, this and other trials have not examined mortality as an outcome. They note that in the United States, the emphasis on influenza vaccine among elderly persons has resulted in an increase in the number of elderly vaccinated from 15% to 20% before 1982 to 62% in 2002. Their study was designed to determine the influenza-related mortality for the past 3 decades with particular attention to adjusting for age and adjusting for seasons dominated by influenza A (H3N2), which dominated in the 1990s. Their study showed that excess all-cause mortality never exceeded 10% for the elderly during the winter months. With regard to influenza-related deaths, persons > 85 years accounted for 24% in the 1970s and for 44% in the 1990s. With regard to the 12 seasons in which influenza A (H3N2) was the dominant influenza strain, there was no evidence for any trend in all-cause mortality. Thus, their data for 33 seasons indicated that influenza-related mortality was always less than 10% of the total number of winter deaths among the elderly. Further, these observations applied to the 1968 pandemic and the severe 1997-1998 season in which there was a mismatch vaccine formulation. For persons aged 65-74 years, excess mortality in the A (H3N2)-predominant seasons fell from 1968 to the early 1980s, but stayed approximately the same thereafter. They conclude that access mortality for persons over 65 years never exceeded 10% in all winter deaths. Consequently, they did not believe that increasing vaccination rates after 1980 could be credited with a decline in mortality rates for any age group. They also conclude that observational studies substantially overestimate the benefits of the vaccine.
Comment: This study was reviewed by Jon Cohen for Science in "News of the Week" ( Science . 2005;307:1026). He notes that the study, not surprisingly, provoked wildly different reactions. Walter Orenstein, former head of the National Immunization Program for the US Centers for Disease Control and Prevention (CDC), concluded that it was a very important and troubling study. By contrast, William Thompson, from the CDC, believed that it was "extremely weak and overstates the results." The conclusion is that this review by Simonsen and associates raises issues about the current US flu vaccine policy and has now stimulated a "hot debate."
http://images.medscape.com/pi/global/ornaments/spacer.gif