Tests find H7N9 replicates well in human lung tissue
A German research team that analyzed and compared H7N9 influenza virus from a diseased human and H7 viruses from birds found that the human strain replicated as well as seasonal flu in lab culture designed to mimic human lung tissue, but the avian H7 strain grew poorly. They reported their findings yesterday in the latest edition of mBio.
The team also found that the H7N9 strain showed low induction of antiviral beta-interferon, which they said is due to efficient suppression of the interferon by the viral NS1 protein.
All of the viruses tested were found mainly in type 2 pneumocytes, which the team wrote is a clue that the H7N9 virus doesn't differ in tissue tropism compared with other human and avian flu subtypes.
The team said the findings add more evidence that the H7N9 virus infecting people in China is adapted to efficient growth in human lung tissue. They also noted that their experimental lung tissue findings complement other studies using animal models and that the approach may be useful for gauging the zoonotic potential of avian flu viruses.
Oct 8 mBio abstract
Study finds low levels of hypersensitivity reactions to H1N1 vaccine
A review of hypersensitivity reactions in people who received the monovalent 2009 H1N1 vaccine found that the rate of events was low, similar to other vaccines, but that levels in women were increased.
The study is based on incidents reported to the federal government's Vaccine Adverse Event Reporting System (VAERS). Researchers are from the Hypersensitivity Working Group of the Clinical Immunization Safety Assessment Network, which includes officials from the US Centers for Disease Control and Prevention (CDC). The team published its findings yesterday in Vaccine.
Experts including seven allergists identified 1,984 possible hypersensitivity events and, based on a review of patient records, verified 1,286 as hypersensitivity disorders. The most common diagnosis was hives/urticaria, followed by anaphylaxis and anxiety.
The overall rate of reported hypersensitivity reactions was 10.7 per million vaccine doses distributed, with a twofold higher rate for live vaccine, the report says.
Though coverage rates for the vaccine were slightly higher in men, women heavily outnumbered men among 20- to 59-year-olds who had a hypersensitivity diagnosis. Women aged 30 to 39 were the hardest-hit group. The gender balance was about even in patients under age 10.
The most common treatment for all conditions was diphenhydramine, and only 51% of 102 anaphylaxis patients with available information received epinephrine, the recommended treatment for severe reactions.
Researchers doubted that the higher reported rate in women could be related to selective reporting, because rates were nearly equal in children and leveled off in older women. They suggested that the difference in adult women could be associated with reproductive hormones or that these women may be at higher risk for certain allergies. More study is needed to explore the suspected hypersensitivity associations, they noted.
Oct 8 Vaccine abstract