Bivalent vaccines are designed to protect against two different strains of a virus or two different viruses altogether. They work by introducing the immune system to antigens from both strains, helping the body to recognize and fight off infections more effectively. This type of vaccine is particularly useful in addressing diseases that have multiple variants, such as the influenza virus or COVID-19. An example of a bivalent vaccine is the COVID-19 bivalent booster, which targets both the original strain of the SARS-CoV-2 virus and newer variants. By providing broader protection, bivalent vaccines can enhance public health efforts and reduce the spread of infectious diseases.