FLU NEWS SCAN: Flu vaccine effectiveness, Tamiflu-resistant H1N1, frailty and vaccine response

May 11, 2011

Study shows high effectiveness of H1N1 vaccine
Using estimates from surveillance data, French researchers determined that the pandemic H1N1 vaccine was 86% effective in preventing confirmed pandemic influenza, compared with 60% for the seasonal flu vaccine. Their effectiveness in preventing influenza-like illness (ILI) was 52% during the pandemic and 33% after for H1N1 vaccine and 61% during and 19% after for seasonal flu vaccine. The study included 838 volunteers in the H1N1 vaccine arm and 856 in the seasonal flu vaccine arm and estimated effectiveness by comparing the proportion of the population vaccinated with the proportion of those who were fully immunized and still contracted influenza or ILI. The authors said their effectiveness data are comparable to published findings and that the lower effectiveness against ILI is not surprising, given that not all ILI is caused by influenza viruses. However, they caution that ILI is a nonspecific endpoint and say other potential limitations with their study are selection biases and bias due to cases not being representative of the population.
May 10 PLoS One study

Delaware reports more Tamiflu-resistant flu cases
Delaware's health department recently reported eight more infections with 2009 H1N1 influenza viruses that are resistant to oseltamivir (Tamiflu), pushing the state's total this season to 14. In a May 9 statement, the Delaware Department of Health and Social Services (DDHSS) reported four of those cases, including in a 45-year-old woman from Sussex County who died. Today Jennifer Wooleyhand, a spokeswoman for the DDHSS, told CIDRAP News that the state had identified four additional cases, of which three are from Sussex County: in a 27-year-old man, a 4-year-old boy, and a 40-year-old man. The fourth new case is in a 44-year-old woman from New Castle County. She said the newest cases have no known relationships, except for living in the same county. (Delaware has only three counties.) The US Centers for Disease Control and Prevention (CDC) has asked Delaware to increase its antiviral-resistance testing, and the DDHSS said the findings will help the CDC revise its recommendations for next year, if needed. Nationally, the CDC's own routine testing of flu isolates since Oct 1 has found 32 2009 H1N1 samples and 2 H3N2 samples that were resistant to oseltamivir, according to its latest update on May 6. Jeff Diamond, a spokesman with the CDC, said the agency asked Delaware to participate in a closer study of oseltamivir-resistant flu viruses, because it has ZIP code and demographic information to include with the samples, the News Journal, based in Wilmington, reported today.
May 9 DDHSS press release
May 6 CDC flu update
Study: Frail elderly respond poorly to flu vaccination
Among elderly people who receive seasonal flu shots, those who are frail have a lower antibody response and a higher subsequent rate of ILI than those who are not frail, according to a study in Vaccine. Researchers from Johns Hopkins University and several other institutions recruited 71 elderly people in the Baltimore area for the study, conducted during the 2007-08 flu season. The average age was 84.5. Using standard criteria, the authors classified 17 participants as frail, 32 as prefrail, and 22 as nonfrail. The volunteers were vaccinated and followed through the season. Their pre-immunization antibody titers were generally high, probably because of previous annual vaccinations, and very few patients seroconverted (had a fourfold increase in antibody titers) after vaccination. Nineteen of the 71 volunteers had an ILI, and post-illness serologic testing indicated flu in 11 of these. ILI and serologically diagnosed flu were significantly more common in the frail than in the nonfrail and prefrail participants. "These results indicate that despite . . .immunization, frailty is associated with significantly higher rates of ILI and influenza infection during the post-vaccination season," the researchers state. They say their findings point up the need for better flu vaccines and preventive strategies for frail community-dwelling elderly people.
May 10 Vaccine study

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