Seasonal Influenza Vaccine Offers Protection Against H7N9 Bird Flu

Man Receiving Flu ShotThe H7N9 avian flu emerged in China in 2013 and sparked fears of a global pandemic. But a new study published in the Journal of Clinical Investigation finds that individuals who receive seasonal flu vaccinations also develop antibodies that protect against the H7N9 bird flu.

Avian influenza A (H7N9) poses an especially strong danger for humans. Symptoms resemble symptoms of the conventional flu including cough, fever, sore throat, muscle aches, headache, and shortness of breath Although no pandemic have yet occurred, the virulent virus has killed one-third of patients hospitalized for the bird flu.

The present study from researchers at the University of Chicago Medicine and the Icahn School of Medicine at Mount Sinai in New York sought to determine whether prior exposure to circulating human influenza viruses or influenza vaccination confers immunity to H7N9 strains.

The researchers selected 83 antibodies, isolated from 28 vaccinated individuals, that reacted with H3N2, a common human influenza strain. Seven percent of the antibodies reacted against rare H7 strains. The vaccines did not contain H7 strains, indicating that seasonal influenza vaccines can offer a wider range of protection against a wide range of influenza strains.

Additionally, three antibodies appeared to completely neutralize H7N9 avian flu. The researchers verified the findings by treating mice with each antibody before exposing the rodents to a lethal dose of H7N9 virus. All three antibodies prevented death in the test mice compared with the control mice, which succumbed to infection. The antibodies also offered protection when administered 24 hours after infection.

The researchers also tested the three antibodies for reactivity against other influenza viruses, finding the antibodies could neutralize H3 and other H7 strains as well.

Comments co-senior author Patrick Wilson, PhD, associate professor of medicine at the University of Chicago:

“We have clear evidence that a normal immune response to flu vaccination offers protection against dangerous and highly unique strains of influenza such as H7N9. We now need to develop ways of amplifying this response.”

The researchers believe that the broad-reactivity results from the location on the influenza virus to which the antibodies bound, highly conserved regions that differ little between strains. Binding to the sites allows the antibodies to neutralize a range of influenza strains despite the notorious ability of influenza viruses to mutate and evade vaccines. Even after mutations occur, the virus remains significantly less infectious.

Explains study author Carole Henry, PhD, postdoctoral fellow at the University of Chicago:

“It appears more common than previously thought for antibodies induced by flu vaccination to offer cross-protection against H7N9. Although they are not always protective, H7-reactive antibodies can be found in almost everyone that’s been vaccinated.”

The researchers are now working to better understand th process and to develop therapeutic approaches based on the antibodies.

Says Wilson:

“The challenge is to exploit this response on a larger scale to make vaccines or therapeutics that offer broad protection against influenza strains. For now, it’s clear that seasonal flu vaccination provides defense against more than just common strains. Everyone should be vaccinated.”

Another recent study found that seasonal flu vaccines may boost immunity to many types of influenza viruses, not just the specific viruses included in each vaccine.


‘Bird flu protection’ given by seasonal flu vaccine:
Preexisting human antibodies neutralize recently emerged H7N9 influenza strains:
Seasonal flu vaccine induces antibodies that protect against H7N9 avian flu:

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