Each year, researchers work to discover new strains of influenza and develop a new vaccine. The procedure is costly and time consuming, which is why scientists for years now have been working to develop a universal flu vaccine. Now, researchers at the Imperial College London have come closer than ever to that goal.

In a new study published in the journal Nature Medicine, the researchers describe how patients with swine flu had less severe reactions if they had more CD8 T cells. T cells are a type of immune cell the body uses to fight viruses. The study suggests that vaccines that cause the body to produce more CD8 T cells could be the key to fighting all types of influenza infections.

“The immune system produces these CD8 T cells in response to usual seasonal flu,” said Ajit Lalvani, leader of the research and a professor at Imperial College London’s National Heart and Lung Institute. “Unlike antibodies, they target the core of the virus, which doesn’t change, even in new pandemic strains. The 2009 pandemic provided a unique natural experiment to test whether T cells could recognise, and protect us against, new strains that we haven’t encountered before and to which we lack antibodies.

“Our findings suggest that by making the body produce more of this specific type of CD8 T cell, you can protect people against symptomatic illness. This provides the blueprint for developing a universal flu vaccine.”

The 2009 pandemic Lalvani refers to is the swine flu outbreak of that year. He and his colleagues took blood and nasal swabs from 342 staff and students at Imperial. As the pandemic wore on, study participants were followed-up on and asked about any flu-like symptoms. Researchers were able to discover how patients with fewer CD8 T cells experienced more severe flu symptoms.