'The Government Must Plan For Mass Vaccinations'

How best to cope with fears of a smallpox terror attack? Proposals to carry out mass public inoculations, a policy dropped 30 years ago, are controversial because of the potential side effects from the live vaccine.

The disease, however, is dangerous: one in three sufferers died before it was declared eradicated in 1980. Its contagious nature, coupled with renewed talk about a possible American war against Iraq-a country suspected of maintaining secret supplies of the virus-have led to questions about the viability of government plans to deal with the threat.

Until last month, federal officials said they would offer limited vaccinations to only a few thousand first-response emergency staff. Last week, officials announced a new plan to start inoculating as many as 500,000 health-care workers who will be on the front lines if new cases develop. Scientists, however, have criticized the government's plans for "ring vaccinations," which would involve isolating infected patients and vaccinating people in close contact with them. One study, written by Edward H. Kaplan, a public-health specialist at Yale University, and the MIT's David L. Craft and Lawrence M. Wein used a mathematical model to determine that mass vaccinations would save thousands more lives than the limited ring vaccinations favored by the government. Their analysis was published this month in the online edition of the Proceedings of the National Academy of Sciences. Kaplan spoke to NEWSWEEK's Arlene Getz about the study and his views on the need for inoculation.

Edward H. Kaplan: Actually, the recommendations from June 20 and the new recommendations to vaccinate half a million first-responders were not issued by the same government bodies. The Advisory Committee on Immunization Practices [ACIP] issued the former recommendations while the latter idea comes from elsewhere in [the Department of] Health and Human Services. So it's not exactly that the same group of people changing their position. The ACIP recommendations are under review by an interagency group. So the final policy is still being debated and shaped at higher levels of government than the ACIP panel, which is basically housed at the Centers for Disease Control.

I would recommend that the government start planning for efficient, local mass vaccinations in the event of an attack. Think of Election Day as an analogy-people know which precinct to vote in, have registered ahead of time, undertake absentee balloting if they know they will be away, etc.

Millions vote on election day. Similarly, vaccination centers need to be located, the population needs to learn their center assignments, informed consent to be vaccinated must be obtained, prescreening for conditions that could lead to vaccine complications could take place. In short, plan now so that if there is an attack, mass vaccination can take place efficiently.

I believe there is an argument for voluntary pre-attack vaccination, though frankly, I am not sure I would choose to do so-unless I was told that without question, ring vaccination would be employed, then I probably would consider getting in line for a smallpox shot. It is true that pre-attack vaccination will make any postattack policy work better by reducing the number of susceptibles in the population.

It is also true that different people have different tolerances for risk. While there is a one in 1 million chance of death from receiving a smallpox vaccine shot, there is also in the United States a 145 in 1 million annual risk of death from a road accident. Those of us who drive do not worry about this risk, and consequently to many an incremental one in a million risk does not seem significant. To others, though, it might be unacceptable. So this is an argument for voluntary vaccination pre-attack.

Our study does not portray smallpox transmission from one or two initial infections in a country where 50 percent to 75 percent of the population is already immune. Our study does portray what would happen in a large city where nobody is immune. It deliberately worries about large outbreaks; the whole point is to find a policy that can contain the consequences of a large-scale bioterror attack. I should point out that ACIP has not conducted an actual analysis of ring vaccination-they have not actually investigated the consequences of their own policy recommendations.

I teach a graduate course at the Yale School of Management called Policy Modeling. In that class, we learn that one does not evaluate the efficacy of a policy by assuming that it works. But those calling our study unrealistic are simply assuming that ring vaccination will work based on historical analogy. The analogy is flawed, both because of the differences in population immunity then and now and also because of the differences between a natural outbreak and a deliberate bioterror attack and also because of the different degrees of mobility in the population then and there versus here and now.

I think the most important thing is to plan for efficient postattack mass vaccinations.

What about the side-effect dangers posed by mass vaccination?

The risks posed by vaccination are not really an issue postattack in a large outbreak. Any policy that can control a large outbreak will of necessity vaccinate a large fraction of the population. Immunocompromised individuals, for example, those battling HIV and cancer, those with eczema, pregnant women, and some others would be at greater risk of a smallpox vaccine complication, so in any planned vaccination, the idea is to screen these people out. This is much easier via mass vaccination, which happens fast, than via ring vaccination, which takes a long time.

The relevant comparison is not between mass vaccination and nothing, it is between mass vaccination and ring vaccination. Postattack, both policies will, unfortunately, allow for the scenario you pose. However, it is important again to consider the consequences of transmitted vaccine consequences. At one ACIP forum I attended at the National Academy of Sciences, it was suggested that about 20 percent of vaccine complications were transmitted.

This sounds scary, but it only raises the total death risk per primary vaccinated person from one in 1 million to 1.33 in 1 million (accounting for all future transmitted fatal vaccine complications). In our analysis, with a population of 10 million, this only leads to an additional three deaths. Compared to the thousands of deaths that result from the proposed ring-vaccination policy, transmitted vaccine complications are just not a major concern.

Smallpox is harder to spread than measles or influenza. It is easier to spread than HIV. Regarding how to weaponize it, I'm not an expert.

Typically the time from infection through symptoms is thought to average 14 days, though of course there will be those who progress much faster and those who take longer. With respect to the four-day window after exposure, the issue is whether a ring vaccination policy can get such persons vaccinated in time. We call this the "race to trace." Unfortunately, if there is a large attack, it could prove very difficult to win this race. For example, even if a contact is instantly named upon the identification of the source of infection, there might be thousands of other contacts already in the process of being located and vaccinated. With ring vaccination, I do not believe the "race to trace" will be won sufficiently often to contain the epidemic.

From what I've been told, by the end of next year the stock should be complete.

Maybe. Maybe not. The real question is, what should we assume the answer to be? I think the proper planning assumption should be that we are all susceptible.

I think it is a fantasy to believe that the control of historical, small, natural outbreaks in areas with high levels of immunity provides guidance for a deliberate, large bioterrorist attack in an area with no immunity. I honestly hope we never have to learn.