Pig Testing For H7N9 To Begin
China’s agriculture authority has expanded the monitoring for the H7N9 strain of bird flu to pigs in order to have a better understanding of the H7N9. Monitoring pigs, in addition to poultry and wild birds, may provide a deeper understanding of H7N9, including its origin, host range, route of transmission and the degree of harm. Experts said that pigs have been included in the plan in an effort to better explore the transmission route, since it is still unknown why and how the bird flu virus infects human beings.
Vaccine Development Challenging
Making a vaccine to protect against the new H7N9 flu virus that has emerged in eastern China could prove to be problematic. Clinical trials of vaccines made to protect against other viruses in the H7 family have shown the vaccines don’t induce much of an immune response, even when people are given what would be considered very large doses.
There hasn’t been enough time to produce even the seed strain to make H7N9 vaccine, let alone small batches of a prototype vaccine for testing. So researchers haven’t had a chance to see how a vaccine against this new flu strain might work in people.
Nancy Cox, the virologist who heads the influenza branch at the U.S. Centers for Diseases Control in Atlanta and CDC flu expert Dr. Tim Uyeki touched on the potential problem in a perspective article on the H7N9 situation published online Thursday by the New England Journal of Medicine.
The perspective accompanied an article by Chinese clinicians describing the first three H7N9 infections that came to light in their country. The article outlines how very sick the patients became and what the genetic sequences of the viruses recovered from them indicate about the path H7N9 took through nature to get to people.
As for the symptoms the illness caused, they included encephalopathy (inflammation of the brain), septic shock, acute respiratory distress syndrome and rhabdomyolysis, which is a breakdown of muscle tissue.
Among the concerning issues about this virus is the question of how a vaccine might work, if one is needed.
A standard dose of flu vaccine is 15 micrograms (mcg). Seasonal flu shots, most of which protect against three strains of flu at once, contain 45 mcg — 15 mcg per strain.
It is generally felt that with a new virus, people would need two shots apiece, given a couple of weeks apart. That’s because the immune system needs to be first introduced to a virus (primed) and then given a second exposure, which boosts the antibodies to protective levels. So in a best case scenario, each person would need twice as much vaccine to protect against a new virus as he or she would get to protect against a seasonal flu strain.