Bioterror Requires New Vaccination Policy

ILLUSTRATION BY ALLEN BREWER

The stepped-up policy will save lives and minimize the impact on the national psyche.

A PAPER BY three academic researchers is being credited with prompting the U.S. government to propose a stepped-up, wide-scale response that would substantially reduce deaths in the event of a bioterrorist attack on a U.S. city.

The government initially proposed a process that called for isolating those infected by the disease and immunizing only those with whom the victims had been in contact. In a case where 1,000 urban Americans were infected with a disease such as smallpox, scholars calculated, the process could result in 4,680 deaths and take a full year to extinguish the outbreak.

A better plan, they said, would be to use speedy mass vaccinations after an attack coupled with advance preparations, which would reduce the death toll in their base case to 560 deaths and halt an outbreak in a much shorter time period. The speedier approach became government policy in September, when a new federal emergency response plan was released.

“The new policy not only saves lives, it minimizes the impact on the national psyche, because many people would otherwise self-quarantine, panic, flee, or storm hospitals demanding vaccinations. The financial costs of such a shutdown would be immense,” says Lawrence Wein, professor of operations, information, and technology and one of three authors of the study, which was published in the August 6 issue of the Proceedings of the National Academy of Sciences.

Wein’s expertise is in the complex logistics of manufacturing, but he also has worked in medical areas such as treatments for HIV, cancer, and Alzheimer’s disease. His coauthors in the smallpox study are Edward Kaplan of the Yale School of Management and David Craft, a doctoral student at MIT. The key feature of their work is to incorporate the timeliness of the response in addition to the spreading pattern of the disease.

The government’s former policy has worked well for containment of natural disease spread in the past, Wein said. “It was motivated by the ‘surveillance containment’ policy that was used to eradicate smallpox worldwide several decades ago. The people who did this are real heroes; this was one of the great health care accomplishments of the past century.”

But applying this policy in a present-day bioterror attack is problematic, Wein says. “The U.S. population lacks herd immunity (meaning it is highly susceptible to smallpox because it has never had it and vaccinations ceased decades ago); tracing human contacts is very difficult in a large city; the smallpox strain is likely to be one that the former Soviet Union weaponized and so will be much more infectious than most historical natural outbreaks; and the United States does not have the leisure of waiting the many months it takes for vaccination to eradicate the disease.”

Embedded in the past response plan is a “race to trace” an infected person, he said. A person infected with the disease would need to self-report to a medical facility and then be isolated and interviewed. On average, people can remember 50 others they may have contacted since being exposed to the illness. Those 50-plus people need to be traced, contacted, and vaccinated.

The problem with this traditional response is time. If a person who is exposed rides the “A” train at 5:15, tracing all those who have been in contact with him is time consuming, if not impossible. And a person is only susceptible to the benefits of the vaccine within about three days of exposure.

The authors are able to calculate the cost in disease spread and added deaths from the lost timeliness by using “queueing theory,” an operations theory long favored by fast-food chains to keep their customers coming back. Queueing theory shows that the more people there are in line for tracing and vaccination, the more difficult it becomes to win the race to trace. “It is the first paper, to our knowledge, that incorporates queueing and operations aspects into a model of an epidemic,” Wein says. “And the repercussions of waiting in a long line are more serious than at McDonald’s.”

Federal officials announced in late September that they were changing the guidelines to reflect the scholars’ recommendations. Meanwhile, the three coauthors are working on other bioterror issues and are discussing pre-attack logistics with public health officials. “We want to make the response as smooth as voting,” Wein said, “so if an attack actually happens, everyone has already been educated and signed consent forms for vaccination. We will know who is contraindicated, and it will just be a matter of people getting in line at their local high school or hospital for treatment.”

—LISA EUNSON

Emergency Response to a Smallpox Attack: The Case for Mass Vaccination, Edward H. Kaplan, David L. Craft, and Lawrence M. Wein, Proceedings of the National Academy of Science (Vol. 99, No. 16), 2002