Designs have been produced for two vaccines that should, in theory, provide immunity against almost all strains of the influenza virus. Such protection has been a dream for medical researchers for many years, and though neither proposals have been tested in animals, let alone in humans, these proposals do avoid problems that have brought other attempts at universal flu vaccines unstuck.
Dr Darren Flower of Aston University, UK, lead an international team in targeting short segments of the flu virus called epitopes. In the journal Bioinformatics, Flower notes that animal studies have found that epitopes that prime the immune system's T cells can provide protection against a wide variety of flu strains. “Epitope-based vaccines aren’t new, but most reports have no experimental validation. We have turned the problem on its head and only use previously-tested epitopes. This allows us to get the best of both worlds, designing a vaccine with a very high likelihood of success.” Flower said in a statement.
Flower and his co-authors used a database of 1,026 influenza epitopes and looked for combinations that might protect against most strains of flu that have been seen in recent years. One vaccine, based on nine epitopes, focused on flu varieties that have been common in the US. A second version was more ambitious, using 11 epitopes in a quest for worldwide protection.
The paper predicts the resulting vaccines could protect against 95 percent of American flu subtypes and 88 percent of those seen worldwide, respectively. Nevertheless, the authors acknowledge that the way epitopes are linked together in a vaccine is crucial if it is to achieve its potential, so while they are seeking partners to make their proposal a reality, the path to do so is not simple.
By referring to unpleasant, but non-lethal, colds as “the flu” we diminish perceptions of how dangerous influenza really is. The real flu virus kills an estimated half a million people a year. The Spanish flu pandemic of 1918-1919 killed tens of millions, and unlike in seasonal outbreaks, it was not only the elderly and those sick with other conditions who died.
Existing vaccines are effective against particular strains of influenza, but the virus mutates so quickly that every year there are new varieties we need inoculating against. Annual injections are recommended to protect against the three strains predicted to be most widespread in a particular season, but even the minority who are vaccinated remain vulnerable to rarer varieties. Moreover, the predictions can be wrong. This year a quadrivalent vaccine (one protective against four strains) was hastily released after virologists became alarmed about a strain not included in the original vaccine.
The most common strategy to build a universal vaccine is to focus on the more stable parts of the proteins on the surface of the virus. Unfortunately, some targeted protein sections have proven less stable than expected, undermining such attempts. Flower's technique has the potential to avoid this problem.
