The arsenal of public health tools to reduce morbidity and mortality from an influenza pandemic is limited. Options include vaccines, antiviral drugs, and interventions such as respiratory protection and social distancing. In a statement The World Health Organization (WHO) described the importance of a vaccination strategy:

“Influenza vaccination is the most important intervention in reducing the impact of influenza, and a key component of the WHO response and preparedness efforts for influenza of pandemic potential, including avian influenza A(H5N1), A(H9N2) and A(H7N9).”

Data for seasonal influenza vaccines and the 2009 A(H1N1)pdm09 vaccines provide a basis for estimating potential effectiveness of A(H7N9) vaccines. Inactivated seasonal influenza vaccines have a pooled efficacy estimate of 59%, primarily for younger adults. A paucity of evidence exists for demonstrating protection in adults aged 65 years or older, particularly with influenza A vaccines.

Three primary scenarios exist for how this A(H7N9) virus outbreak will unfold:

1. The virus could disappear in the animal reservoir, ending new human cases
2. The virus could persist in the animal reservoir, resulting in sporadic human infections.
3. The virus could, through mutation or reassortment, become readily transmissible between humans, resulting in a global pandemic.


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