New vaccines against currently circulating influenza variants are required every year due to the diversity of flu viruses and variable efficacy of vaccines to prevent them. A universal vaccine would eliminate the need to create a vaccine for each year's variants. The efficacy of a vaccine refers to the protection against a broad variety of influenza strains. Events such as antigenic shift have created pandemic strains such as the H1N1 outbreak in 2009. The research required every year to isolate a potential popular viral strain and create a vaccine to defend against it is a six-month-long process; during that time the virus can mutate, making the vaccines less effective.
High-risk populations, including the elderly and those with chronic disease, often acquire only limited immunity towards the flu from vaccines. The vaccines have been found to be 30% to 70% effective in preventing hospitalization from the flu or pneumonia.
On average influenza vaccine efficacy is 60% among the general population that receive yearly vaccinations.
A universal vaccine could be manufactured in quantity and eliminate availability and supply issues of current vaccines. There is conflicting evidence on whether it would cut costs.