By UTMB’s Dr. Richard Rupp and Bridget Hawkins: Traditional flu vaccines protect from three strains of the flu while the newest formulations offer protection from four strains. A mismatch occurs when the current vaccine does not cover the predominant flu strains circulating around a community. Many flu strains circulate every flu season. The strains differ across regions of countries and around the globe. Information about the different strains is collected by 141 flu-monitoring centers located in 111 countries. Forecasting the next season is not easy. Researchers are trying to improve the forecasts by using the growing body of knowledge about flu strains, our immune systems and population dynamics. Still, the underpinnings of the mismatch problem persist. The real answer is a universal vaccine that covers all flu strains. It couldn’t come too soon.