Seasonal Flu Vaccine May Provide Protection against Deadly Avian Strain

Global pandemics are often the backdrop for many Hollywood dystopian films, but for infectious disease researchers the threat society faces from rapid transmission of deadly diseases is all too real. As recently as 2013, an influenza strain from China sparked fears as a global killer, due to its unusually high mortality rate.    

Now, scientists from the University of Chicago and Icahn School of Medicine at Mount Sinai believe they have found evidence of cross-protection against the deadly H7N9 strain of avian influenza, in patients receiving seasonal flu shots.

The results from this study were published in the Journal of Clinical Investigation under an article entitled “Preexisting human antibodies neutralize recently emerged H7N9 influenza strains”.
H7N9 is uncommonly dangerous to humans with a mortality rate of approximately 30%, surpassing even the 1918 Spanish flu that killed more than 50 million people worldwide. Since threats from these deadly influenza strains are ever present, the researchers began to focus on seasonal flu vaccinations, in order to search for potential therapeutic targets.  

“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,” said Patrick Wilson, Ph.D., associate professor of medicine at the University of Chicago and co-senior author on the study. “We now need to develop ways of amplifying this response.”

Dr. Wilson and his team chose 83 antibodies, which they isolated from 28 individuals who received seasonal flu shots and had a positive response to H3N2, a common human influenza strain. They found that 7% of the antibodies reacted against the rare H7 strains, which are not included in seasonal flu vaccinations.

This was an interesting and exciting initial finding for the investigators. Upon further analysis the researchers found that three of the antibodies provided complete protection against H7N9. Specifically, the team vaccinated mice with each antibody and then challenged them with a lethal dose of H7N9. In all cases the mice were protected and the antibodies prevented death, while control mice all succumbed to infection. Additionally, the antibodies could provide protection when used as a therapeutic intervention, when administered 24 hours after mice were infected with H7N9.  

“It appears more common than previously thought for antibodies induced by flu vaccination to offer cross-protection against H7N9,” explained Carole Henry, Ph.D., postdoctoral fellow at the University of Chicago and co-author on the study. “Although they are not always protective, H7-reactive antibodies can be found in almost everyone that's been vaccinated.”

The efficacy of these antibodies notwithstanding, the researchers are still unsure why they are produced in low abundance. For now however, Dr. Wilson and the team are focusing on developing therapeutic approaches based on their data from the antibodies they found. 

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