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zoom RSS 最近2年間の子どもへのインフルエンザワクチンはほとんど効果なし/米国

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 セントルイス大の最新の研究で、最近2年のインフルエンザシーズンで、5才以下の子どもに対するインフルエンザワクチンは入院や受診数の減少がなく効果がなかったとわかった。流行株とワクチン株が一致せず、不活性化したワクチンは子どもには上手く効果が働かなかった。対照的に、鼻スプレーとして与えられた弱毒生ワクチンはずっとより効果的で、ウイルスに小さな変異がおきても50%以上の有効率であるという。
 しかし、別の研究で、インフルエンザに関連したブドウ球菌感染によって起こされた死亡が米国の子供の間に増加しているとわかり、インフルエンザワクチンは重要であるだろう。
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Kids' Flu Shot Largely Ineffective Over Past Few Years
Study finds it didn't keep them from hospitals, doctors' offices
By Steven Reinberg, HealthDay Reporter
http://health.msn.com/health-topics/infectious-diseases/articlepage.aspx?cp-documentid=100217533

画像Study finds it didn't keep them from hospitals, doctors' offices.

MONDAY, Oct. 6 (HealthDay News) -- Over the past two flu seasons, vaccinating children five and younger did not reduce the number of child hospitalizations or doctor's visits linked to influenza, according to results of a new study.

Given the poor match between the flu vaccine and circulating strains during the last two years, "this finding is not surprising," said Dr. Robert Belshe, a professor of medicine and pediatrics and director of the Center for Vaccine Development at the Saint Louis University Medical Center, who was not involved in the study.

"We know that the inactivated vaccine -- the flu shot -- doesn't work real well in children, particularly when the virus has evolved and drifted away from the type that is put in the vaccine," he said.

In contrast, the live attenuated vaccine given as a nasal spray is far more effective, Belshe contended. "A recent study showed that it is 50 percent more effective at protecting against flu, including these drifted viruses that don't match," he said.

Another study, this time in the October issue of Pediatrics, found that deaths caused by flu-linked staph infection are climbing among U.S. children, so the flu shot may still be important.

In June 2006, the Centers for Disease Control and Prevention (CDC) recommended for the first time that all children 6 months of age or older receive annual flu shots.

The new report was published in the October issue of the Archives of Pediatrics & Adolescent Medicine.

In the study, a team led by Dr. Peter G. Szilagyi, from the University of Rochester School of Medicine and Dentistry and Strong Memorial Hospital in Rochester, N.Y., looked at 414 children aged five and younger who developed flu in the 2003-2004 or 2004-2005 flu seasons.

Among these children, 245 were seen in hospitals or emergency departments, and 169 were cared for in a doctor's office or clinic. The researchers compared the vaccination status of these children with more than 5,000 children from the same area who did not get the flu.

Szilagyi's group found that children who got the flu were less likely to have been vaccinated, compared with children who didn't get sick.

However, after they adjusted for flu risk factors -- such as a child's location, sex, insurance status, chronic health conditions or timing of the vaccine -- the effectiveness of the vaccine could no longer be shown. The effectiveness of the flu shot ranged from 7 percent to 52 percent for 6- to 59-month-old children who had been fully vaccinated, the researchers found.

The less-than-perfect match between the strain of flu in the vaccine during the two seasons studied and the flu that was actually circulating may have contributed substantially to the poor effectiveness of the vaccine, Szilagyi's team speculated.

In 2003 to 2004, 99 percent of circulating flu was influenza A, but only 11 percent of the influenza A strain in the United States was similar to the strains included in the vaccine.

"The 2004-2005 season was less severe, and the vaccine was a better match to circulating strains than in 2003-2004, but still only 36 percent of virus isolates were antigenically similar to vaccine strains," the authors noted.

From September 2007 to April 2008, the CDC reported a total of 72 deaths from flu among children with many more hospitalized.

Belshe said that, for children over two, the nasal flu vaccine should be used instead of an injection. "It is recommended for children and adults, aged 2 to 49 who do not have asthma or recurrent wheezing -- that's about 80 percent of children," he said.

For younger children, "you're stuck with a flu shot -- no pun intended," Belshe said. "The flu shots should still be used. It probably modifies the severity of the illness, even though it doesn't protect completely against the illness itself -- it is important to take," he said.

Dr. William Schaffner, department chairman of the division of infectious disease and professor of preventive medicine at Vanderbilt University, noted that to be fully protected, young children need two doses of flu vaccine, which many don't get.

"Adults have had much more experience with both influenza and influenza vaccine," Schaffner added. "The likelihood that the vaccine is going to give you a boost in immunity is stronger in adults than it is in children," he said.

Schaffner noted that over the past 20 years, the match between the vaccine and the circulating flu virus has generally been good.

"In about four-fifths of the time, the experts have been pretty much on target, including the appropriate material in the vaccine. Occasionally, because the flu is fickle, it outfoxes those of us who select what's going to be in the vaccine," Schaffner said.

As for the coming flu season, the CDC in September announced that it was "optimistic" that the vaccine created this time around will be a closer match to circulating viruses.

"It's not a great vaccine, [but] it's a good vaccine. The best tool we have is the influenza vaccine -- recognizing that every once in a while, getting your influenza vaccine is not going to give you perfect protection," he said.

And any protection may be vital, according to the study in Pediatrics. In that work, researchers at the CDC analyzed data on pediatric flu deaths from the 2004-2005 season through to the 2006-2007 season.

They found that the number of kids who died of the flu over the three seasons rose from 47 and 46 in the first two years, to 73 in the 2006-2007 season. Many of the deaths were attributed to tough-to-treat staph infections. More than half of the children who died were between 5 and 17 years of age and had previously been healthy, the team noted.

The overall risk to an individual child is still very low, "but it's an important message to say even healthy children develop complications and die almost before anything much can be done for them," one vaccine specialist, the Mayo Clinic's Dr. Gregory Poland, told the Associated Press.

Schaffner stressed that vaccination is still important, but he agreed with Belshe that the nasal spray vaccine is better for children.

"The nasal spray vaccine provides broader protection against influenza virus variants than does the injectable vaccine," Schaffner said. "There are many of us who would like to see more children vaccinated and more nasal spray vaccine used. Any vaccine is better than none. Nasal spray vaccine should be used more frequently."

More information

For more about flu, visit the Centers for Disease Control and Prevention.
SOURCES: Robert Belshe, M.D., professor, medicine and pediatrics, and director, Center for Vaccine Development, Saint Louis University Medical Center, St. Louis, Mo.; William Schaffner, M.D., department chairman, division of infectious disease, professor of preventive medicine, Vanderbilt University, Nashville, Tenn; October 2008, Archives of Pediatrics & Adolescent Medicine; Oct. 6, 2008, Associated Press

Copyright © 2008 ScoutNews, LLC. All rights reserved.

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Influenza Vaccine Effectiveness Among Children 6 to 59 Months of Age During 2 Influenza Seasons
http://archpedi.ama-assn.org/cgi/content/full/162/10/943
A Case-Cohort Study

Peter G. Szilagyi, MD, MPH; Gerry Fairbrother, PhD; Marie R. Griffin, MD, MPH; Richard W. Hornung, DrPH; Stephanie Donauer, MS; Ardythe Morrow, PhD; Mekibib Altaye, PhD; Yuwei Zhu, MD, MS; Sandra Ambrose, MBA; Kathryn M. Edwards, MD; Katherine A. Poehling, MD, MPH; Geraldine Lofthus, PhD; Michol Holloway, MPH; Lyn Finelli, DrPH, MS; Marika Iwane, PhD, MPH; Mary Allen Staat, MD, MPH; for the New Vaccine Surveillance Network

Arch Pediatr Adolesc Med. 2008;162(10):943-951.

ABSTRACT

Objective To measure vaccine effectiveness (VE) in preventing influenza-related health care visits among children aged 6 to 59 months during 2 consecutive influenza seasons.

Design Case-cohort study estimating effectiveness of inactivated influenza vaccine in preventing inpatient/outpatient visits (emergency department [ED] and outpatient clinic). We compared vaccination status of laboratory-confirmed influenza cases with a cluster sample of children from a random sample of practices in 3 counties (subcohort) during the 2003-2004 and 2004-2005 seasons.

Setting Counties encompassing Rochester, New York, Nashville, Tennessee, and Cincinnati, Ohio.

Participants Children aged 6 to 59 months seen in inpatient/ED or outpatient clinic settings for acute respiratory illnesses and community-based subcohort comparison.

Main Exposure Influenza vaccination.

Main Outcome Measures Influenza vaccination status of cases vs subcohort using time-dependent Cox proportional hazards models to estimate VE in preventing inpatient/ED and outpatient visits.

Results During the 2003-2004 and 2004-2005 seasons, 165 and 80 inpatient/ED and 74 and 95 outpatient influenza cases were enrolled, while more than 4500 inpatient/ED and more than 600 outpatient subcohorts were evaluated, respectively. In bivariate analyses, cases had lower vaccination rates than subcohorts. However, significant influenza VE could not be demonstrated for any season, age, or setting after adjusting for county, sex, insurance, chronic conditions recommended for influenza vaccination, and timing of influenza vaccination (VE estimates ranged from 7%-52% across settings and seasons for fully vaccinated 6- to 59-month-olds).

Conclusion In 2 seasons with suboptimal antigenic match between vaccines and circulating strains, we could not demonstrate VE in preventing influenza-related inpatient/ED or outpatient visits in children younger than 5 years. Further study is needed during years with good vaccine match.

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Published online October 1, 2008
PEDIATRICS Vol. 122 No. 4 October 2008, pp. 805-811 (doi:10.1542/peds.2008-1336)
http://pediatrics.aappublications.org/cgi/content/abstract/122/4/805
ARTICLE
Influenza-Associated Pediatric Mortality in the United States: Increase of Staphylococcus aureus Coinfection
Lyn Finelli, DrPHa, Anthony Fiore, MDa, Rosaline Dhara, MPHa, Lynnette Brammer, MPHa, David K. Shay, MDa, Laurie Kamimoto, MDa, Alicia Fry, MDa, Jeffrey Hageman, MPHb, Rachel Gorwitz, MDb, Joseph Bresee, MDa and Timothy Uyeki, MDa

a Influenza Division, National Center for Immunization and Respiratory Diseases
b Division of Healthcare Quality Promotion, National Center for Preparedness, Detection, and Control of Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia

OBJECTIVE. Pediatric influenza-associated death became a nationally notifiable condition in the United States during 2004. We describe influenza-associated pediatric mortality from 2004 to 2007, including an increase of Staphylococcus aureus coinfections.

METHODS. Influenza-associated pediatric death is defined as a death of a child who is younger than 18 years and has laboratory-confirmed influenza. State and local health departments report to the Centers for Disease Control and Prevention demographic, clinical, and laboratory data on influenza-associated pediatric deaths.

RESULTS. During the 2004–2007 influenza seasons, 166 influenza-associated pediatric deaths were reported (n = 47, 46, and 73, respectively). Median age of the children was 5 years. Children often progressed rapidly to death; 45% died within 72 hours of onset, including 43% who died at home or in an emergency department. Of 90 children who were recommended for influenza vaccination, only 5 (6%) were fully vaccinated. Reports of bacterial coinfection increased substantially from 2004–2005 to 2006–2007 (6%, 15%, and 34%, respectively). S aureus was isolated from a sterile site or endotracheal tube culture in 1 case in 2004–2005, 3 cases in 2005–2006, and 22 cases in 2006–2007; 64% were methicillin-resistant S aureus. Children with S aureus coinfection were significantly older and more likely to have pneumonia and acute respiratory distress syndrome than those who were not coinfected.

CONCLUSIONS. Influenza-associated pediatric mortality is rare, but the proportion of S aureus coinfection identified increased fivefold over the past 3 seasons. Research is needed to identify risk factors for influenza coinfection with invasive bacteria and to determine the impact of influenza vaccination and antiviral agents in preventing pediatric mortality.

Key Words: influenza • influenza vaccine • mortality rates • Staphylococcus aureus

Abbreviations: CDC―Centers for Disease Control and Prevention • ACIP―Advisory Committee on Immunization Practices • MRSA―methicillin-resistant Staphylococcus aureus

Accepted Jul 1, 2008.

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