Developing a reliable flu vaccine for seasonal flu shots has remained an enduring challenge for the healthcare sector. Flu vaccines for a particular year are determined by the WHO, which tracks the trending strains of the flu virus. However, due to the longwinded process of vaccine production, the choice of the flu strains to be targeted has to be made months in advance. This provides a huge window of opportunity for the flu virus being grown in laboratories, which mutates at a rapid rate and thus usually escapes the attention of the medical authorities. This results in low success rates of the flu vaccine, with the 42% success rate of the flu vaccine in 2015-16 season being considered a significant upgrade over usual figures.
“Bivalent” Flu Virus Models Provide Way Forward
The main problem in developing the flu vaccine is that the virus tends to mutate during the production of the vaccine. A sufficiently mutated virus can go beyond recognition for the vaccine intended to work on it, rendering the vaccine useless. Scientists discovered this problem fairly recently, with the habitually low efficacy of the flu vaccine having remained a mystery for so long. The virus needs a different-shaped key to enter chicken eggs, which are used in the mass production of the targeted strain, than in humans, forcing it to mutate to adapt to its new surroundings. However, hemagglutinin, the ‘key’ in question, is also present in flu vaccines that induce an immune response, giving the mutating virus an ever-increasing headstart over the vaccine’s development process.
Senior author of the study, Nicholas S. Heaton, developed two varieties of hemagglutinin, one adapted for eggs and one for humans, and made single viri capable of expressing both. This removed the pressure on the human-adapted hemagglutinin variant to modify, as the egg-adapted hemagglutinin was used in reshaping the virus for the eggs. This develops a major advance in flu vaccine development, as it prevents the targeted strains of the flu virus from mutating beyond recognition during the development process of the vaccine.