Influenza, commonly known as ‘the flu’, is a contagious respiratory illness caused by influenza viruses (types A, B, C, D); only influenza type A viruses are known to cause flu pandemics. Vaccination has been shown to reduce flu morbidity and mortality, as well as the high economic burden associated with flu illness. According to the US Centers for Disease Control and Prevention (CDC), the 2022/2023 flu vaccine reduced the risk of influenza A-related hospitalisation among children and adults and provided significant protection against flu-related illness and flu-related emergency room (ER) visits; these benefits were observed across all age groups. GlobalData epidemiologists expect that the findings of this CDC report indicate that there will likely be an increase in influenza-related hospitalisations averted by the seasonal flu vaccine this season.
The February CDC report analysed data from three networks: the New Vaccine Surveillance Network (NVSN), Flu and Other Viruses in the Acutely Ill Network (IVY), and VISION Network. The NVSN includes seven study sites, IVY includes 22 medical centres, and VISION includes 367 health facilities across the US. These networks were included to examine vaccine effectiveness against laboratory-confirmed flu-associated outpatient visits, ER visits and hospitalisations. In the NVSN, from September 2022 to January 2023, flu vaccinated children were 68% less likely to be hospitalised due to flu illness or related complications, and 42% less likely to visit an ER due to flu-related illness. Similarly in IVY, from October 2022 to January 2023, flu vaccinated adults were 43% less likely to be hospitalised due to flu illness or related complications. Further, elderly adults ages 65 years and above were 35% less likely to have a flu-related hospitalisation, while adults 18–64 years were 51% less likely to have a flu-related hospitalisation. Finally, in VISION, from October 2022 to January 2023, flu vaccinated adults were 44% less likely to visit an ER or urgent care centre, and 39% less likely to be hospitalised due to flu illness or related complications.
GlobalData epidemiologists forecast that influenza-related hospitalisations averted by vaccination will reach approximately 115,000 by the end of 2023. However, these forecast estimates will likely be surpassed, as this year’s flu vaccine has substantially reduced flu-related hospitalisations and improved patient outcomes across all age groups compared with previous seasons. While this is promising, it should be noted that the 2022/2023 flu season was more severe and peaked earlier than previous seasons; flu activity remains low at this time, but vaccination is still recommended as long as the flu continues to circulate in the community.