Study: GBS risk much higher with flu than with flu vaccine
The risk of Guillain-Barre syndrome (GBS) after flu vaccination was much lower than the risk of GBS after flu infection, according to a study today in Lancet Infectious Diseases.
Canadian researchers used a self-controlled study design and data from universal healthcare systems in Ontario from 1993 through 2011. They determined exposures to flu vaccine and flu illness from physician billing claims.
They identified 2,831 patients admitted for GBS, 330 of whom received a flu vaccine and 109 of whom had an influenza-coded healthcare encounter 42 weeks or less before hospitalization.
The risk of GBS within 6 weeks after vaccination was 52% higher than in the control interval of 9 to 42 weeks (relative incidence 1.52; 95% confidence interval [CI], 1.17-1.99), with the greatest risk during weeks 2 through 4 post-vaccination. The risk of GBS within 6 weeks after an influenza diagnosis, however, was much higher (15.81; 95% CI, 10.28-24.32).
The attributable risks were 1.03 GBS admissions per million vaccinations, the researchers noted, compared with 17.2 GBS admissions per million flu diagnoses.
"Patients considering immunisation should be fully informed of the risks of Guillain-Barre syndrome from both influenza vaccines and influenza illness," the authors concluded.
Jun 28 Lancet Infect Dis abstract
No H5N1 found in Alaska birds, but state has possible entry point
Researchers say they found no highly pathogenic (HP) H5N1 avian flu viruses in four years of monitoring wild birds in a part of western Alaska where three flyways converge. But they did find some low-pathogenicity flu viruses with Eurasian genes, which supports the view that HP viruses could enter North America in that area.
The Yukon-Kuskowim Delta is an important breeding ground for many bird species, said a press release yesterday from the US Geological Survey (USGS), which worked on the study with the US Fish and Wildlife Service (USFWS) and several local partners. They launched their study after H5N1 was found in wild birds in China in 2005 and published their findings in the July issue of the Journal of Wildlife Diseases.
From 2006 through 2009, the researchers tested more than 24,000 samples gathered from 82 bird species in the Yukon-Kuskowim Delta and found 90 low-pathogenicity viral strains in samples from 11 species, according to the report. At least one gene segment in 39% of the isolates had a Eurasian origin.
Target species—those ranked as having a relatively high potential to bring HP H5N1 to North America—were no more likely than non-target species to carry viruses with Eurasian-origin genes.
Subsistence hunters in 11 local villages provided many of the bird samples used in the study, a USFWS official said in the press release.
Jun 27 USGS press release
July J Wild Dis abstract