Preventing and Controlling Influenza with Available Interventions (New Eng Jour Med)

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Preventing and Controlling Influenza with Available Interventions

Timothy M. Uyeki, M.D., M.P.H., M.P.P.
N Engl J Med 2014; February 27, 2014

Influenza activity has been surging in the United States, and there are reports of critical illness and death in young and middle-aged adults. The predominant virus so far this season is influenza A(H1N1)pdm09, the cause of the 2009 H1N1 pandemic. Despite many challenges, there is much that the public, patients, the public health community, and clinicians can do now to reduce influenza's impact.

The spread of influenza A(H1N1)pdm09 virus suggests that despite its ongoing circulation since 2009, population immunity is not sufficiently high and many people remain susceptible. To date, surveillance data provide no evidence of significant antigenic drift in the circulating virus strains, so susceptibility could be due to the presence of a substantial number of previously uninfected and unvaccinated persons or to waning immunity from prior infection.

Although previously healthy persons can have severe illness, certain groups are at increased risk for complications that can result in severe illness: children younger than 2 years of age, elderly people, pregnant women, people with certain chronic conditions (e.g., pulmonary, cardiac [excluding hypertension], renal, hepatic, metabolic, hematologic, neurologic, or neuromuscular conditions, immunosuppression, or morbid obesity), nursing home residents, American Indians, and Alaska Natives.1 The highest hospitalization rates for seasonal influenza typically occur among people 65 years of age or older, followed by children younger than 5 years of age; influenza-attributable mortality is highest among those 65 years of age or older.1 During the 2009 H1N1 pandemic, mortality was high among hospitalized middle-aged adults2; since influenza A(H1N1)pdm09 virus is prevalent this season, young and middle-aged adults, women who are pregnant or up to 2 weeks post partum, and people with underlying conditions, including morbid obesity, may also be at particularly high risk for severe complications.2

Annual influenza vaccination is recommended for everyone 6 months of age or older in the United States.1 Prevention strategies for infants younger than 6 months of age include vaccinating pregnant women and vaccinating all household members and caregivers (“cocooning”). The effectiveness of influenza vaccine varies depending on several factors, including the recipient's age and immune response and the match between circulating virus strains and vaccine strains. In recent years, influenza vaccine has been moderately effective, though less so among elderly persons, and some vaccinated persons may still develop influenza.1 To date, circulating influenza A(H1N1)pdm09 virus strains are well matched by the H1N1 strains in all available vaccines this season, and unvaccinated persons should be vaccinated as soon as possible.

http://www.nejm.org/doi/full/10.1056/NEJMp1400034?query=TOC

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