Human immune systems were ill-prepared for the swine flu virus that spread across the globe in 2009. The lack of pre-existing immunity left people vulnerable but, researchers wondered, was everyone equally unprotected? Answering this question has led to a 'blueprint' for a universal flu vaccine.
The blueprint was developed by a team of British researchers, who, seeing the potential to run a unique natural experiment, tracked 342 healthy adults through the 2009 pandemic. Writing in Nature Medicine, the researchers explain that T cell levels at the start of the pandemic were compared to the intensity of flu symptoms. The comparison showed higher levels of a certain type of T cell were associated with less severe symptoms, suggesting the immune system was able to fight the virus.
Identifying how the T cells fought a virus they had never encountered before gave the researchers an idea of how to build a universal vaccine. "We know the exact subgroup of the immune system and we've identified the key fragments in the internal core of the virus. These should be included in a vaccine ... We know what needs to be in the vaccine and we can just get on and do it," study lead professor Ajit Lalvani told the BBC.
The 'internal core' of the virus is key as this is where unchanging elements are found. Inducing an immune response against these components, which are found in multiple viral strains, will offer broader protection than when the evolving outer shell is targeted. There is, however, a big difference between knowing which parts to target, and having a successful vaccine. The weak antibody response from T cell vaccines is one anticipated stumbling block. Even so, Lalvani believes a universal flu vaccine could be just 5 years away.