however, achieving this has proven to be very difficult, and a number of new strategies are now undergoing investigation.

Responding to Marketplace and Policy Issues

Numerous economic and public health policy issues complicate efforts in vaccine development, production, and deployment. In the last 40 years, few pharmaceutical manufacturers have considered vaccines an attractive business opportunity because of the low return on investment and the exposure to legal liability (Rappuoli et al., 2002). Companies perceive little market incentive to develop vaccines for diseases that occur sporadically and affect the poorest populations—vaccines that may also have little chance of being employed effectively. This has certainly been seen in the area of tropical diseases, especially arthropod- and rodent-borne diseases. Even if inexpensive and efficacious vaccines or drugs are developed, their use by those most in need may be hampered by a lack of public health infrastructure. For example, a safe and effective vaccine for yellow fever has existed for decades. Yet this disease continues to be a pathogen of significant importance in humans in Africa and South America, and its emergence remains a constant threat in urban areas of the tropics and potentially even in Asia, where it would represent a public health catastrophe (Monath, 2001).

The infrastructure for the manufacture of vaccines is steadily deteriorating, and shortages currently exist even in the availability of certain routine vaccines. For example, the difficulty of producing sufficient influenza vaccine in extremely mild interpandemic years, such as 2000 and 2001, signals a potential disaster during a pandemic year. In 2000, supplies of the tetanus and diptheria booster fell short. By the fall of 2001, CDC was reporting shortages of five vaccines, some of which are combination vaccines that protect against eight childhood diseases. Of the eight recommended routine childhood vaccines, five are produced by a single major manufacturer; consequently, if supply is interrupted or a manufacturer ceases production, there may be few or no alternative sources of vaccine (GAO, 2002). The reality is that the infrastructure does not exist to produce even a sufficient supply of currently licensed vaccines, let alone to develop new vaccines against emerging microbial threats. Thus in the event of an outbreak—whether naturally occurring or an act of bioterrorism— the United States will not have the capacity to produce sufficient vaccines to safeguard the population.

The anthrax attacks of 2001 in the United States generated widespread public awareness of infectious agents that had previously not been regarded as worthy of much public attention or substantial federal research funding. Before September 2001, several infectious agents had been identified as

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