made the discovery that influenza virus may be cultured in hen embryonated eggs. This prompted research into the properties of the virus and the creation and application of inactivated vaccines in the late 1930s and early 1940s. Inactivated vaccines' usefulness as a preventative measure was proven in the 1950s. Later, 2003 saw the approval of the first live, attenuated influenza vaccine. Looking into influenza B specifically, Thomas Francis Jr. isolated influenza B virus in 1936. However, it was not until 1940 when influenza B viruses were discovered. In 1942, a new bivalent vaccine was developed that protected against both the H1N1 strain of influenza A and the newly discovered influenza B virus. In today’s current world, even while some technology has advanced and flu vaccines now cover both strains of influenza A and B, the science is still based on findings from almost a century ago. The viruses included in flu vaccines are changed each year to match the strains of flu that are most likely to make people sick that year since flu viruses can develop swiftly and new mutations have appeared each year, like H1N1. Even though there are two different lineages of influenza B viruses that circulate during most seasons, flu vaccinations were long meant to protect against three different flu viruses: the influenza A(H1N1), influenza A(H3N2), and one influenza B virus. The second lineage of the B virus was since added to provide greater defense against circulating flu viruses. Two influenza A viruses and two influenza B viruses are among the four flu viruses that a quadrivalent vaccine is intended to protect against. All flu vaccines in the United States today are quadrivalent. The four main types of Type A and B influenza viruses that are most likely to spread and make people sick during the upcoming flu season are the targets of seasonal influenza (flu) vaccines. All of the available flu vaccinations in the United States offer protection against the influenza A(H1), A(H3), B/Yamagata, and B/Victoria lineage viruses. Each of these four vaccine virus components is chosen based on the following criteria: which flu viruses are infecting people ahead of the upcoming flu season, how widely they are spreading, how well the vaccines from the previous flu season may protect against those flu viruses, and the vaccine viruses' capacity to offer cross-protection. For the 2022-2023 flu season, there are three flu vaccines that are preferentially