RISKS POSED BY H5N1
Human infection with avian H5N1 virus was first noted in Hong Kong in 1997. Of eighteen people known to be infected, six died. All of the infected people had close contact with domestic birds.1 Data suggest that human-to-human transmission of H5N1 is extremely inefficient, and that avian flu cannot currently be spread among people by coughing or sneezing (small particle aerosol transmission).2 Instead, transmission to people results from direct con-
However, in the worst case scenario, the human-to-human spread would pave the way for pandemic infection, such as the influenza pandemics of 1918, 1957, and 1969. As the debate continues, it is clear that the risk must be taken seriously, and that we must start preparing for a possible avian flu pandemic now.
The US government has appropriated $7 billion to prepare for the threat of an avian flu pandemic, earmarking funds to treat infected populations, contain outbreaks, and — most importantly — prevention. H5N1 currently can be treated with neuraminidase inhibitor drugs such as Roche's oseltamivir (Tamiflu), and clinical trials are under way for BioCryst's neuraminidase inhibitor Peramivir. But there have been reports of resistance to this type of drug therapy.2 Government stockpiling of effective antiviral agents and other first-line patient care necessities, such as ventilators, is an important component of the response. Tamiflu is a scarce resource, leading some policy makers to suggest compulsory licensing of Roche's patents on the drug as a way to alleviate the shortage. While the limited amount of the raw ingredient used to produce Tamiflu is considered an impediment to increased manufacture, there is another reason to reject compulsory licensing.€It threatens to rob pharmaceutical companies of the returns they need to support their R&D investments that produce other innovative products.4
Vaccine development holds the greatest promise of protecting the worldwide population from an avian flu pandemic. Two experimental vaccines (manufactured by Sanofi-Aventis and Chiron) against H5N1 are in clinical trials sponsored by the National Institute of Allergy and Infectious Disease. Both vaccines are made from inactivated H5N1 viruses.5 While early results have been encouraging, many challenges remain.6
INCENTIVIZING VACCINE DEVELOPMENT
The ability to use a vaccine to prevent a pandemic hinges on developing a safe and effective vaccine to protect against infection, and on the percentage of the at-risk population that becomes vaccinated. Vaccines are administered to healthy individuals to protect against an uncertain risk. These individuals are unlikely to take a vaccine if they perceive that their risk of falling ill from the infection is less than the risk of being harmed by the vaccine. Concerns about their ability to recover economic damages arising from vaccine-induced harm further reduce the propensity of many individuals to be vaccinated. On the other hand, vaccine manufacturers are unlikely to undertake the economic and technical burdens associated with creating a vaccine if they perceive that an insufficient market exists or that liability exposure reduces their ability to earn a fair return on their investment.