Influenza is a common, yet potentially deadly viral disease that persistently afflicts the global population. During the most recent influenza season in the United States, there were about 49 million cases of influenza illness, with about 960,000 cases requiring hospitalization and about 79,000 fatal cases (CDC, 2018). According to the Centers for Disease Control (CDC), influenza is responsible for over $10.4 billion in direct annual costs for hospitalization and outpatient visits in the United States alone (O’Brien, 2017). Children under the age of 5, especially those under the age of two, individuals ages 65 and older, pregnant women, and residents of nursing homes are among those most at risk of experiencing flu-related complications, such as pneumonia and bronchitis (CDC, 2018). The national and global burden of influenza has urged efforts seeking improved protection.

The disease is caused by type A (IAV), type B (IBV), and type C (ICV) influenza viruses, and disease strains linked with the IAV and IBV types are known to affect the population seasonally and with the most severity (Koutsakos, 2019). Seasonal influenza vaccinations aim to protect vaccinated individuals against the specific viruses expected to be most prominent in the given year. However, they fail to provide immunity for all viral strains, thus requiring annual administration. Extensive scientific efforts have been directed towards searching for a vaccine that offers more long-term and comprehensive protection. A recent study published in Nature Immunology on February 18, 2019 by the researchers at the University of Melbourne in Australia described the discovery of CD8+T cells, “killer cells,” capable of fighting all types of the virus (Koutsakos, 2019). The breakthrough points to the promising possibility of a universal flu vaccine.

The researchers explored and analyzed the immune memory as well as cross-protection and cross-reactivity of CD8+T cells against IAV, IBV, and ICV strains of influenza (Koutsakos, 2019). Immune memory involves recalling specific antigens of previous exposure. Cross-reactivity is the ability of antibodies activated by particular antigens to possess affinities for multiple antigens, and cross-protection is the protection and immunity against the infection as a result of cross-reactivity.. CD8+T cells are a type of white blood cell that recognize epitopes, which consist of a virus specific peptide complex with a type of glycoprotein known as human leukocyte antigens (HLAs), on the surfaces of infected cells to target them to kill (Koutsakos, 2019). 31 epitopes for IAV and IBV strains and eight for IAV, IBV, and ICV strains were identified, from which nine were selected for use in the study. It was concluded that three of these epitopes were shared across IAV, IBV, and ICV flu strains. CD8+T cells were isolated from blood and lung tissue from healthy and infected humans. Mice were given a vaccine boosted with peptides that activate CD8+T cells prior to infection with an IBV form of influenza. CD8+T cell activity was observed, as well as effects such as the reduction of inflammation in the mice. The study revealed the heterotypic cross-reactivity and wide cross-protective abilities of CD8+T cells amongst all influenza strain types with the potential to provide influenza immunity to approximately 54 percent of the global population (Koutsakos, 2019). The discovery urges the development vaccines that specifically induce CD8+T cells responses for influenza.

A universal influenza vaccination with the potential to protect against all disease strains would be economically advantageous and serve to significantly reduce those infected each year, thus diminishing the impact of influenza on the global burden of disease. While this vaccine may not yet be a tangible reality, enticing advances such as a swelling knowledge and understanding of “killer cells” and continual research indicate its hopeful prospects.


  1. Centers for Disease Control and Prevention. (2018, December). About the Flu. Centers for Disease Control and Prevention. Retrieved from
  2. Koutsakos, Marios. (2019). Human CD8+T cell cross-reactivity across influenza A, B and C viruses. Nature Immunology. Retrieved from
  3. O’Brien, Sarah. (2017, October 30). Getting the flu can wreak havoc on your finances. CNBC. Retrieved from

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