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Seasonal influenza vaccination in adults

Patricia L Hibberd, MD, PhD
Section Editor
Martin S Hirsch, MD
Deputy Editor
Anna R Thorner, MD


Influenza is an acute respiratory illness caused by influenza A or B viruses. It occurs in epidemics nearly every year, mainly during the winter season in temperate climates. Influenza viruses change their antigenic characteristics frequently, and their subsequent spread depends upon the susceptibility of the population to viruses with novel antigens. Annual influenza vaccination is an important public health measure for preventing influenza infection [1-4]. The protection provided by influenza vaccines is based upon induction of virus-neutralizing antibodies, mainly against the viral hemagglutinin.

The role of influenza vaccination in the prevention of seasonal influenza will be reviewed here. The use of influenza vaccine in immunocompromised hosts, pregnant women, patients with chronic liver disease, patients with end-stage renal disease, healthcare workers, and travelers is discussed separately. (See associated topic reviews.)

The clinical manifestations and diagnosis of influenza in adults, the role of antiviral agents for the prevention and treatment of seasonal influenza, and vaccines against the 2009 pandemic H1N1 influenza ("swine influenza") virus, H5N1 avian influenza, and H7N9 avian influenza are also reviewed elsewhere. Seasonal influenza vaccination in children is also presented separately. (See "Clinical manifestations of seasonal influenza in adults" and "Diagnosis of seasonal influenza in adults" and "Prevention of seasonal influenza with antiviral drugs in adults" and "Treatment of seasonal influenza in adults" and "Treatment and prevention of pandemic H1N1 influenza ('swine influenza')", section on 'Vaccination' and "Avian influenza vaccines" and "Avian influenza A H7N9: Treatment and prevention", section on 'Vaccine development' and "Seasonal influenza in children: Prevention with vaccines".)


Influenza activity — The United States Centers for Disease Control and Prevention (CDC), in collaboration with the World Health Organization (WHO) and its reporting network, tracks influenza virus isolates throughout the world to monitor disease activity and to predict the appropriate components for the annual influenza vaccine. Surveillance information, which is updated weekly during influenza season, is available on the CDC website. In addition, FluNet, a database for global influenza virus surveillance, is available on the WHO website. The typical seasonal trends of influenza activity in the United States are shown in the following figure (figure 1).

Indications — The United States Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccination for all individuals six months of age and older [2,5]. High-risk individuals, their close contacts, and healthcare workers should remain high-priority recipients in vaccination campaigns (table 1). (See 'High-priority groups' below.)


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