Reasonable Rascal
07-10-02, 13:05
SMALLPOX VACCINATION STRATEGIES - USA
***************************************
A ProMED-mail post
Date: Mon, 8 Jul 2002 15:30:26 -0700
Source: The New York Times 8 Jul 2002 [edited]
<http://www.nytimes.com/2002/07/08/health/08CND-SMAL.html>
Study Uses Math Model to Determine Effects of a Smallpox Attack
----------------------------
A new study finds large differences in how 4 different vaccination strategies would fight a smallpox terror attack, with the best resulting in 440 deaths and the worst 110 000 deaths.
The study used a mathematical model to compare how an attack on a large city that infected 1000 people would progress when countered with diverse vaccination plans meant to halt the spread of the highly contagious disease.
In all cases, the mass vaccination of the United States population worked far better than limited local immunizations, a strategy the federal government has tended to prefer.
"We find that mass vaccination results in both far fewer deaths and much faster epidemic eradication," the authors conclude. In the best case, the epidemic was stopped in 115 days and in the worst 350 days.
The new analysis is being published this week in the online edition of Proceedings of the National Academy of Sciences. Its authors are Edward H. Kaplan, a public health specialist at Yale University, and David L. Craft and Lawrence M. Wein, both of the Massachusetts Institute of Technology.
Ever since smallpox was eradicated from human populations decades ago, federal officials have resisted mass vaccination because the vaccine uses a live virus that can cause severe side effects and even kill. In the days of wide vaccination, roughly one person in a million died.
But federal policy is in flux because of fears of bioterrorism. Although today only Russia and the United States have declared stocks of the virus, experts say clandestine supplies probably exist.
Most people are now considered vulnerable because immunity is thought to wane over time. The United States stopped routine vaccinations in 1972. Smallpox kills roughly 1 in 3 victims who are unvaccinated.
Vaccination can save even infected people because the vaccine, if given within 4 days of exposure to the virus, halts the disease's advance.
The new study, coming amid rising criticism of federal policy in recent months, claims to be the first to make detailed comparisons of the vaccination options. It is an elaboration of a preliminary presentation that Dr. Kaplan gave at a federal meeting in Washington on 15 Jun 2002.
The study found the least effective method to be "ring vaccination," the main way smallpox was eradicated from human populations. It consists of isolating infected patients and vaccinating people found to be in close contact with them, forming a ring of immunization around any outbreak and a barrier to its further spread.
In the hypothetical attack, ring vaccination resulted in 367 000 cases of smallpox and 110 000 deaths and took 350 days to extinguish the outbreak.
By contrast, mass vaccinations carried out as soon as authorities became aware of the attack (smallpox takes roughly 2 weeks to incubate in the body and show symptoms) would result in 1830 cases and 560 deaths over a period of 115 days.
The study found that if the authorities were overwhelmed and decided belatedly to switch from ring to mass vaccination on the 33rd day of the crisis, the fatalities would still be quite high 15 570 cases and 4680 deaths.
"The cost of waiting," the authors said, "is very high - 4,120 incremental deaths."
The study found that the vaccination of the United States population before an attack worked best of all to cut fatalities.
If only 40 percent of the population were immunized beforehand, the same attack followed by wider mass vaccinations would produce 440 deaths. But if followed with ring vaccinations, the result would be 40 000 deaths.
"We believe that unless pre-attack vaccination is used," the authors conclude, serious consideration should be given to dropping federal plans for ring vaccination in favor of mass immunizations "in the event of a smallpox attack in a large urban center."
[Byline: William J. Broad]
--
ProMED-mail
[Because the study referred to in this article was not yet available on line, it is prudent to withhold comment, other than it will be very interesting to see the study and the actual analyses and premises on which the analyses are based. As an aside, if there were to be an aerosolized release of the smallpox virus in a well-circumscribed geographic area, a mass campaign for vaccination of the entire population in the affected area is a form of "ring vaccination" -- viewing the geographic area as "the case" to vaccinate a ring around -- a semantic issue. - Mod.MPP]
--------------------------------------------------
Comments: As noted in the quotation from the forthcoming report the "ring vaccination" plan may be the least effective response to an actual outbreak, in particular because such an event would be almost certainly due to a deliberate bio-release. Such an event would almost certainly fail to mimic a naturally occurring outbreak from the beginning as the aim is to infect as many people within a short time as possible. Thus, rather than a few isolated cases within a small locus one might expect to see dozens or hundreds infected within a broad area.
In the era of rapid transit travel the certainty of infected cases traveling, and thus potentially exposing others, seems certain. While it is current wisdom that patients are not infectious until the obvious lesions appear it is quite possible that during a small window when the pox first begin to appear vs. when they become widespread and obvious that initial recognition of the illness may lag.
In order for ring vaccination to be effective it literally requires declaration of martial law, and isolation of entire areas if not cities. The economic consequences of such as event would alone cause severe disruption, and it is likely that local travel restrictions would themselves result in non-smallpox deaths as persons requiring specialized care for other illnesses/injuries would be restricted from leaving the hot zone for fear of spreading infection. One has to wonder if this has been factored into the quoted mathematical model.
There is also the consideration that the Russians successfully developed recombinant forms of smallpox with new characteristics, even going so far as to splice the virus in combination with other infectious viruii. This is well enough documented to be a certainty, vis a vis' Ken Alibek (a BioPreparat Vice-Chief) and others involved in the Russian programs. With the demonstrated lack of security surrounding radioactive materials in the former USSR one can easily see how bio materials may have likewise been "lost" to persons unknown over the course of the past 10 years. To date no one can account for literally tons of weaponized smallpox produced as late as the early to mid 1990's.
In light of this study one would hope that the subject of voluntary innoculation would again be looked at. To date it seems it has been discounted owing to political liability concerns rather than actual health concerns. Simple screening of individuals with immuno-suppressive disorders would eliminate many of the potential severe reactions that are often touted as reason to not implement such a program. At least with a voluntary program the patient is given the chance to provide informed consent vs. being forced to partake in a mandatory program or face temporary incarceration/isolation as is part of the current response plan.
RR
***************************************
A ProMED-mail post
Date: Mon, 8 Jul 2002 15:30:26 -0700
Source: The New York Times 8 Jul 2002 [edited]
<http://www.nytimes.com/2002/07/08/health/08CND-SMAL.html>
Study Uses Math Model to Determine Effects of a Smallpox Attack
----------------------------
A new study finds large differences in how 4 different vaccination strategies would fight a smallpox terror attack, with the best resulting in 440 deaths and the worst 110 000 deaths.
The study used a mathematical model to compare how an attack on a large city that infected 1000 people would progress when countered with diverse vaccination plans meant to halt the spread of the highly contagious disease.
In all cases, the mass vaccination of the United States population worked far better than limited local immunizations, a strategy the federal government has tended to prefer.
"We find that mass vaccination results in both far fewer deaths and much faster epidemic eradication," the authors conclude. In the best case, the epidemic was stopped in 115 days and in the worst 350 days.
The new analysis is being published this week in the online edition of Proceedings of the National Academy of Sciences. Its authors are Edward H. Kaplan, a public health specialist at Yale University, and David L. Craft and Lawrence M. Wein, both of the Massachusetts Institute of Technology.
Ever since smallpox was eradicated from human populations decades ago, federal officials have resisted mass vaccination because the vaccine uses a live virus that can cause severe side effects and even kill. In the days of wide vaccination, roughly one person in a million died.
But federal policy is in flux because of fears of bioterrorism. Although today only Russia and the United States have declared stocks of the virus, experts say clandestine supplies probably exist.
Most people are now considered vulnerable because immunity is thought to wane over time. The United States stopped routine vaccinations in 1972. Smallpox kills roughly 1 in 3 victims who are unvaccinated.
Vaccination can save even infected people because the vaccine, if given within 4 days of exposure to the virus, halts the disease's advance.
The new study, coming amid rising criticism of federal policy in recent months, claims to be the first to make detailed comparisons of the vaccination options. It is an elaboration of a preliminary presentation that Dr. Kaplan gave at a federal meeting in Washington on 15 Jun 2002.
The study found the least effective method to be "ring vaccination," the main way smallpox was eradicated from human populations. It consists of isolating infected patients and vaccinating people found to be in close contact with them, forming a ring of immunization around any outbreak and a barrier to its further spread.
In the hypothetical attack, ring vaccination resulted in 367 000 cases of smallpox and 110 000 deaths and took 350 days to extinguish the outbreak.
By contrast, mass vaccinations carried out as soon as authorities became aware of the attack (smallpox takes roughly 2 weeks to incubate in the body and show symptoms) would result in 1830 cases and 560 deaths over a period of 115 days.
The study found that if the authorities were overwhelmed and decided belatedly to switch from ring to mass vaccination on the 33rd day of the crisis, the fatalities would still be quite high 15 570 cases and 4680 deaths.
"The cost of waiting," the authors said, "is very high - 4,120 incremental deaths."
The study found that the vaccination of the United States population before an attack worked best of all to cut fatalities.
If only 40 percent of the population were immunized beforehand, the same attack followed by wider mass vaccinations would produce 440 deaths. But if followed with ring vaccinations, the result would be 40 000 deaths.
"We believe that unless pre-attack vaccination is used," the authors conclude, serious consideration should be given to dropping federal plans for ring vaccination in favor of mass immunizations "in the event of a smallpox attack in a large urban center."
[Byline: William J. Broad]
--
ProMED-mail
[Because the study referred to in this article was not yet available on line, it is prudent to withhold comment, other than it will be very interesting to see the study and the actual analyses and premises on which the analyses are based. As an aside, if there were to be an aerosolized release of the smallpox virus in a well-circumscribed geographic area, a mass campaign for vaccination of the entire population in the affected area is a form of "ring vaccination" -- viewing the geographic area as "the case" to vaccinate a ring around -- a semantic issue. - Mod.MPP]
--------------------------------------------------
Comments: As noted in the quotation from the forthcoming report the "ring vaccination" plan may be the least effective response to an actual outbreak, in particular because such an event would be almost certainly due to a deliberate bio-release. Such an event would almost certainly fail to mimic a naturally occurring outbreak from the beginning as the aim is to infect as many people within a short time as possible. Thus, rather than a few isolated cases within a small locus one might expect to see dozens or hundreds infected within a broad area.
In the era of rapid transit travel the certainty of infected cases traveling, and thus potentially exposing others, seems certain. While it is current wisdom that patients are not infectious until the obvious lesions appear it is quite possible that during a small window when the pox first begin to appear vs. when they become widespread and obvious that initial recognition of the illness may lag.
In order for ring vaccination to be effective it literally requires declaration of martial law, and isolation of entire areas if not cities. The economic consequences of such as event would alone cause severe disruption, and it is likely that local travel restrictions would themselves result in non-smallpox deaths as persons requiring specialized care for other illnesses/injuries would be restricted from leaving the hot zone for fear of spreading infection. One has to wonder if this has been factored into the quoted mathematical model.
There is also the consideration that the Russians successfully developed recombinant forms of smallpox with new characteristics, even going so far as to splice the virus in combination with other infectious viruii. This is well enough documented to be a certainty, vis a vis' Ken Alibek (a BioPreparat Vice-Chief) and others involved in the Russian programs. With the demonstrated lack of security surrounding radioactive materials in the former USSR one can easily see how bio materials may have likewise been "lost" to persons unknown over the course of the past 10 years. To date no one can account for literally tons of weaponized smallpox produced as late as the early to mid 1990's.
In light of this study one would hope that the subject of voluntary innoculation would again be looked at. To date it seems it has been discounted owing to political liability concerns rather than actual health concerns. Simple screening of individuals with immuno-suppressive disorders would eliminate many of the potential severe reactions that are often touted as reason to not implement such a program. At least with a voluntary program the patient is given the chance to provide informed consent vs. being forced to partake in a mandatory program or face temporary incarceration/isolation as is part of the current response plan.
RR