Oct 22, 2012
Dallas-area pandemic school closure associated with lower rate of disease
Aschool closure in the Dallas–Ft. Worth, Tex., area was associated with lower rates of acute respiratory illness (ARI) and flu-related emergency department (ED) visits during the 2009 H1N1 flu pandemic, according to a study in Clinical Infectious Diseases. Researchers from the Dallas–Ft. Worth area and the US Centers for Disease Control and Prevention compared data on parent-reported ARI and ED visits for self-reported flu before, during, and after an Apr 30 to May 7, 2009, school closing in a district in Tarrant County (which includes Ft. Worth) with data from a district in Dallas County (home to Dallas) that did not shutter schools. They found that, although ARIs and ED flu visits both climbed in both school districts, the increase in ARI rates was 45% lower in the Tarrant County district: It went from 0.6% before the intervention to 1.2% during it, compared with 0.4% to 1.5% for the Dallas County district. The rate of ED flu visits in the Tarrant County district rose from 2.8% before the school closure to 4.4%, compared with an increase from 2.9% to 6.2% during the same period in Dallas County. The authors point out that the two counties have similar demographics but emphasize that their study did not assess lab-confirmed influenza.
Oct 19 Clin Infect Dis abstract
Flu vaccine was 62% effective over 4 years in Australian study
Australian researchers who conducted case-control studies over five influenza seasons found that seasonal flu vaccines were 62% effective in protecting working-age adults, according to a report in Influenza and Other Respiratory Viruses. From 2007 through 2011, researchers recruited adults aged 20 to 64 from sentinel general practices in Victoria state and conducted prospective case-control studies using the test-negative design with PCR-confirmed flu as the endpoint. The adjusted vaccine effectiveness (VE) over all years except 2009, the pandemic year, was 62% (95% confidence interval, 43%-75%), which the authors call moderate protection. By virus type, the VE estimates ranged from 31% for seasonal H1N1 to 88% for pandemic H1N1. The authors also compared VE estimates with the match between the vaccine and circulating strains, as assessed by hemagglutination inhibition assays. In 2007, when the match was "incomplete," overall VE was estimated at 58%. But in 2011, when the match was assessed as good, the overall VE was almost the same, at 59%. "VE estimates correlated poorly with circulating strain match, as assessed by haemagglutination inhibition assays, suggesting a need for VE studies that incorporate antigenic characterization data," the report says.
Oct 19 Influenza Other Respi Viruses report