tion campaign. Participants from across the nation met in Raleigh, North Carolina; Austin, Texas; and Seattle, Washington, to review, evaluate, and learn from their experiences during the vaccination campaign. The 2009 H1N1 vaccination campaign was one of the biggest public health initiatives in U.S. history, and a thorough and critical evaluation of the campaign presents an important opportunity to examine the nation’s response to a public health threat and to identify useful lessons, promising practices, and other strategies to improve future emergency vaccination campaigns.

Background: Preparing for the Vaccination Campaign

In April 2009, the first cases of a new strain of influenza A—referred to as the 2009 H1N1 influenza—were detected in California. Because of the potentially severe health consequences of a pandemic influenza, the detection of these cases set off a coordinated wave of activity across the public health system to minimize public health consequences.2 Each year in the United States, between 5 and 20 percent of the population is infected with the seasonal flu, and on average approximately 24,000 people die of flu-related causes (range 3,300 to 48,600) (CDC, 2010c). However, in a pandemic, the infection rate and death toll can be much higher. The pandemic of 1918 killed an estimated 50 million people worldwide (about 3 percent of the global population) and approximately 675,000 people in the United States alone (CDC, 2010d). Pandemics also occurred in 1957 and 1968, although they were less severe.

Adding to the sense of urgency, previous pandemic response planning efforts had largely focused on influenza A virus subtype H5N1. Unlike 2009 H1N1, H5N1 has a low human-to-human transmission rate but a very high mortality rate; more than half of humans known to have been infected with the current Asian strain of H5N1 avian influenza died from it (WHO, 2006). The surveillance and laboratory systems developed by the Centers for Disease Control and Prevention (CDC) as part of these planning efforts were responsible for the early detection of 2009

2

According to the Centers for Disease Control and Prevention, “An influenza pandemic occurs when a new influenza A virus emerges for which there is little or no immunity in the human population, begins to cause serious illness, and then spreads easily person-to-person worldwide. A pandemic is determined by spread of disease, not its ability to cause death” (CDC, 2010b).



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