Quest for Universal Flu Vaccine (IMAGE) Stanford University School of Engineering Caption The flu virus changes each year. Today's vaccines target specific strains of flu prevalent in a given year. This image shows the HA protein from three flu strains. The HA protein is the target for current vaccines. This protein has a head and a stem. Current vaccines target the head. The blue and yellow dots depict the amino acids that make up the HA protein. The yellow dots show amino acids that change in the 1934 and 2009 protein, relative to the 1918 variant. There are more changes in the head than in the stem. Stanford researchers are developing a flu vaccine based on the stem of the HA protein. If successful, this could yield a vaccine that protects against different strains of flu, and perhaps for more than one year at a time. Credit Yuan Lu, Stanford University Usage Restrictions Please use with credit and attribution License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.