**INTRODUCTION**

The recent efforts for pandemic influenza preparedness at local, country, and international levels exemplify rapid, research‐driven creation and execution of an agenda for a disease of international concern. A prominent part of the research on a potential pandemic of influenza has focused on strategies to prevent or mitigate such an event. Much of this research has been highly technical and not adequately surveyed such that policymakers can make choices fitting the context of their city or country. This paper reviews this field, focusing on policies to control – i.e., prevent or mitigate – a human pandemic of influenza, and presents the major conclusions from the literature.

A rationale for this literature review is that research on the effectiveness of control policies is driving multilateral and national strategies at three levels. First, the World Health Organization (WHO), and the EU and US agencies responsible for pandemic preparedness have recommended strategies ( _sets of policies_ ) for controlling a human pandemic of influenza. The recommended actions in certain contexts aim at containing an outbreak rapidly before it can spread; in others the emphasis is on mitigating the overall attack rate. The WHO has recently issued an Interim Protocol for containment measures under the title _Rapid Operations to Contain the Initial Emergence of Pandemic Influenza_<sup>1</sup> . Recommended policies here substantially derive from insights from mathematical modeling studies<sup>3,5</sup> that compare policies for containing pandemic outbreaks. Second, there are studies focusing on particular policies, such as limiting international air travel, vaccination, or community‐level policies. These studies have informed specific WHO guidelines, e.g., for recommending a restriction on flights from certain cities; as well as country governments’ choices of implementing such guidance. Third, policymakers have learned from research on the 2003 SARS outbreak. The emphasis on these three background literature sources in this review follows the order in which they were mentioned.

Before the aims of this review can be discussed, it is necessary to clarify some nomenclature. In general, effectiveness for a containment–focused strategy refers to the reduction of the spread of pandemic influenza within a country or internationally. For a mitigation strategy, effectiveness refers to reducing the overall number of cases, i.e., the attack rate, and to delay and reduce the peak rate of cases per day. A mitigation strategy lowering the overall illness attack rate unambiguously reduces hospitalizations and deaths that are related to human and economic losses. For two strategies achieving similar reductions, the one more feasible is more effective. In this review, effectiveness of a policy (used here interchangeably with ‘intervention’) is differentiated from baseline _efficacy,_ as established in theory or in the laboratory. Efficacy is an important determinant of policy effectiveness in modeling studies. However, effectiveness accounts for likelihood of use, feasibility, transmission dynamics, etc., in an outbreak or an epidemic. Given the rationale above and the definition of terms, this review has three specific aims as specified below.

- I. Link in one document the current research on the efficacy of specific policies; the properties of a potential pandemic‐capable influenza virus relevant to its infectiousness and virulence; the assumptions and methods behind mathematical or other models of pandemic influenza spread and control; and the results of studies of the effectiveness, cost (or cost‐effectiveness), and ethical dimensions of policies and strategies. For example, such linkage can help refer the claims of modeling studies to the baseline efficacy of particular policies, and to assess the generalizability of the results given modeling assumptions, the assumed properties of the virus, etc.

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