Expert debates merits of maintaining smallpox stockpile

D. A. Henderson, the American epidemiologist who led the international effort for smallpox eradication, recently examined the costs required to manufacture and maintain a new smallpox vaccine stockpile, and therefore the rationale for maintaining the existing stockpile of the virus.

Henderson’s commentary, published in the journal Biosecurity and Bioterrorism: Biodefense Strategy, Practice, and Science. comes in anticipation of the May 2011 World Health Assembly meeting that will decide the fate of the world’s two remaining smallpox stockpiles in the United States and Russia.

The recommendation that the stockpiles be destroyed was made by the World Health Organization Expert Committee on Smallpox in 1994, and was supported by numerous agencies and experts on the issue. Four separate postponements of virus destruction have been made to facilitate further research.

As of November 2010, a WHO Advisory Group of Independent Experts and the WHO Advisory Committee on Variola Research have concluded that the only compelling reason to keep the smallpox stocks available is to meet restrictive regulatory requirements for vaccine and drug development.

Henderson maintains that the risk of another smallpox outbreak is small, but not zero. Escape from the two containment facilities is diminishingly small considering the stringent security measures. Though there is no way of knowing for sure, it is not believed that smallpox exists outside of the two laboratories, but should terrorists acquire a sample and develop the skills needed to release it, a vaccine should be available.

The two existing licensed vaccines are, to Henderson, well-suited to contain an outbreak for reasons other than the high level of protection that they provide. There is a good reason to believe that they are well-suited in protecting against the strains that would be encountered under natural circumstances, methods of production have been planned and the vaccines’ shelf life is considered exceptional.

The primary drawback of the existing vaccines, according to Henderson, is the occurrence of sometimes serious adverse reactions in certain people. Work is proceeding on safer vaccines, but Henderson said that the cost of their development is prohibitive.

Securing the resources needed to develop and stockpile a new vaccine is a major barrier. An even larger barrier in a developing a new vaccine is that there is no way that one can be certain that it will adequately protect someone from developing smallpox or be effective in treating smallpox illness.

In the past, vaccines and antiviral medications were tested during an epidemic, but smallpox no longer plagues the world. For a disease so virulent, there is an understandable apprehension against using medicines that have not been fully tested.

With limited resources available, Henderson questions large investments into new smallpox vaccines and antiviral drugs. He said it is better to give priority to assuring that there is an adequate emergency reserve of smallpox vaccines and antiviral drugs on hand that are certain to protect against the disease, and in strengthening international response capabilities for surveillance and containment. Ultimately, Henderson believes maintaining the existing stockpiles is unnecessary for moving in this direction.