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Eradication as a Strategy

In this video, Olakunle Alonge weighs the benefits and downsides of eradication vs control for polio. (Step 1.11)
OLAKUNLE ALONGE: So we’re going to talk a little bit more about eradication of this strategy. So again we’ve talked about the vaccine. We’ve talked about the polio virus in and of itself. We talked about by the clinical manifestation of the polio virus. We’ve talked about the history of the polio and polio disease. And we’ve also talked about the two vaccines and the two different types of vaccines and the relative advantages and disadvantages of these two different types of polio vaccines. And indeed because we have the vaccine, because we have resources and the ability to surveil and to detect cases, eradication in of itself is the strategy.
It’s a [INAUDIBLE] strategy though that is made possible because of the availability of vaccines for polio. So we go back to the discussion around a debate between control versus eradication. So let’s think about polio as an eradication strategy. Again the goal to eradicate polio. So why eradication. Why not other types of goals? Why not elimination? Why not control? There are different challenges or different goals that you can aim to achieve for addressing an infectious disease like polio. So one is control. Control would be the scenario where you bring down the disease to an acceptable level. So that is to say, yes the disease is still common within the population.
But you’re able to reduce the morbidity and mortality due to the disease to an acceptable level. So for this you require ongoing prevention measures and treatment measures to curtail the disease. And this is different from eradication which is really the goal to completely eliminate the disease-causing agent from the face of the world. So you really want to eliminate the incidence of the disease to zero. But that is to say that no individual, no one on Earth will be able to get the disease. And if you are able to achieve this, you can actually stop the prevention measures or for control. You can’t stop vaccination. You can stop treatment. And so on. So all prevention measures can permanently end.
An elimination is very similar to eradication. The only difference is just that you achieve the same as you achieve for eradication but within a limited geographical boundary. So either within a country or within a region. So why eradication for polio? Why not control? Why not elimination? And the answer to that is we go back to some of the criteria for or indicators for eradicating a disease. So one of the things about eradicating a disease is that you really want to be sure that eradication is possible. And eradication is possible based upon the biological concentration of the disease including the fact that humans should be the only [INAUDIBLE] for the disease.
So that once you eliminate the disease among human population, then you would have achieved eradication. And there’s no chance of amplification of the disease-causing agent within the environment. So earlier on, I was stunned that polio existed among only humans and it was also taught that the polio virus can only amplify within humans. And therefore eradication was set as the strategy. Even though as time went on, we begin to understand the biology of the virus even more. And there are reasons to believe that the virus can, in some regard, amplify within the environment. Either in the human host or just in close proximity to the human host. And this actually prevents challenge to the eradication goal.
And then again, the other notion is that you should have political commitments across different countries, across different regions, at different levels in order to achieve eradication. And all of this took place as far back as in 1988, when the Global Polio Eradication Initiative was set. Over the years, there’s been some dynamic changes in our understanding of the biology of the disease. There’s been a lot of changes to the commitments on the political level in terms of leadership at country level, at national level, at regional level. And so on. That has really questioned the eradication goal for the polio program.
But again the program is close to achieving eradication given that over 99% of the cases have declined for polio over the course of the 30 years at the Global Polio Eradication Initiative has been in place. Eradication is really difficult, as you can imagine. I mean, it’s not just for you to have a vaccine. It’s not just for you to have an effective vaccine. The vaccine has to be delivered. So there’s a lot of implementation and consideration that has to be true in terms of delivering the vaccine. And then the vaccine has to be delivered all children all eligible population across the world. So you have to do that across different geographies, different boundaries.
And then you have scenarios where there’s different governor structures and political structures in different countries. So you have to work within those political contexts. There are different cultural beliefs, different societal norms. You have to work within the societal norms. You have to overcome the areas of a plain view that are post by that. And then there are different individuals that are involved from the parents, the caregivers, to the health workers to the administrator at district and regional and national level, to actors at global level, and so on. So you have all of these working together as a complex system. So the eradication programs are difficult because it requires implementation within a very complex system.
And therefore, there have been very few examples of a successful eradication program. So we know that there have been at least seven different programs that have been candidate for eradication or diseases that I’ve been candidates for eradication. And only one of them has succeeded and that’s the smallpox eradication. And the smallpox eradication is unique in and of itself because of the nature of the virus that causes smallpox. It’s a DNA virus. It’s more stable than having a virus that is polio before his start. And there are clinical manifestation for smallpox in almost all of the cases that get smallpox. You are able to identify cases.
You are able to quarantine cases that really set in preventive measures in addition to the vaccine. For some of these other diseases, they don’t have some of these clinical purposes. So for polio for instance, we see that in majority of cases you don’t see the infection. So therefore it becomes difficult for you to identify cases to isolate cases and so on. And therefore some of these other diseases either have other issues and challenges. The eradication goal is good. Eradicating diseases or setting up an eradication program are indeed very difficult. And the polio program provides us with very useful lessons for our future eradication activities and also for the global health programs.
Like I mentioned earlier on polio is harder than the smallpox to eradicate for some of the reasons that I described. One the biology of the virus. So smallpox virus is DNA. And DNA viruses must die around the viruses. So the extent to which they change genetic material is less frequent. And therefore vaccines are able to confer protection in the mist of regaining virulence as we have with the polio virus. It’s really unlikely for the smallpox. And the second thing is the clinical manifestation of smallpox. It’s classical. And you see lashes, patients that are healed. And this allows you to wrap to readily identify cases, and to isolate cases, and to quarantine the cases and the close contact to the cases.
And you can put in other measures outside of vaccination to control the disease. And this helped with the eradication of the smallpox. Unlike the polio, it’s not every case that has polio that manifest. So you really don’t know. And therefore it becomes difficult for you to isolate or quarantine and to do ring-fencing immunization as was done with smallpox. So again the biology of the virus itself, the chemical manifestation of the virus, and then also the eradication needs to happen within a timely fashion. You can imagine that when you are trying to achieve eradication and this becomes protracted because attention wins, commitment wins over time. Resources also wins. So it becomes more challenging.
And that’s one thing that has happened to the polio program. There’s been a lot of challenges over the years, which has really impacted on the commitments both at a political level and the implementation level in specific countries to sustain the effort. There are other examples as well. But I really want you to take a pause and reflect on some of this in just comparing the polio and the smallpox eradication initiatives. again, just to emphasize that polio eradication is truly an enormous endeavor that requires coalition, collaboration at the global level. So you need to think about it in terms of the scope, the time, the resources which requires implementation of evidence supported intervention across different settings both social, political, economic settings.
It requires activities and coordination at various levels, at the global level, at the regional level, at the national level, at the sub-national level. It requires many actors. So here you see in this picture a natural administering polio or a polio vaccine to a child in a train in India. And indeed you see there’s a lot of people involved. So from the parents of the child to the health worker to the supervisors to the district officers to people who do surveillance to political leaders who makes policies at different levels. So there are different actors that are involved.
And because of the the peculiarity of the different contexts, we also require different forms of strategies to facilitate and to overcome the areas across different contexts. So eradication as strategy, eradication as a goal, it’s an undertaking that is not to be taken lightly. It’s something that requires the best science, the best knowledge to try to implement. And also commitment over time across different levels. This slide is really for us to highlight how the global polio eradication campaign has intensified in recent times. So you would see that like the chain in 1988 and 2008, the Global Polio Eradication Initiative achieved a rapid decline in the number of cases of polio from about 350000 cases to about 1500 cases.
And then between 2008 to 2018, it was a lot harder to reduce the cases because of a specific contextual issue within this population. So over that period activities for mass immunization kind of ramped up rapidly. And this slide and the map that you see really shows to you how campaigns, and needless to say activities by which we vaccine workers and health workers go from door to door, or go to a specific location to immunize and deliver the vaccine to children intensify over time. So you see the intensity shaded by the color. So looking at the African region, you will see that the darker shade of blue is really where you have between five to nine campaigns by child.
This is to say that a child in that year received a vaccine from a campaign program that requires health workers to go door to door, house to house, or from location to location, between five to nine times within the year. So indeed it shows to you the skills of what it would entail to achieve that. I mean this occurred in places like Niger Republic in Africa. You see in West Africa one of the darkest shade in Chad. In West Africa, it’s Sudan. In parts of North Africa. And then the next dark shade of blue really shows to you where the campaign occurred between three to five parents per child.
And then the lighter shade we had about two to three or between one to two campaigns per child per year. So again it shows to you the intensity. So not only do you have two set in all of these actors, all of these mechanisms alive for a particular point in time. You have to do it repeatedly over time within the same population. And therefore, given the nature of the disease, it’s really important that no child is left out. It’s really important that every child that is susceptible, every eligible population receive the vaccine. So you have to achieve perfection, even given all of the challenges that are posed by the different contexts in which the program has to be implemented.
Because just missing out one child, or missing out two children, or missing out a couple of villages, we will hum poppy the eradication goal. So, there’s a zero allowance of missing any child or a population. So therefore, to achieve eradication as a goal in order to extinct diseases from the patient you have, perfection is essential. And then to think about achieving perfection across different contexts, across different boundaries, really allows you to see how difficult and how challenging the polio eradication initiative has been. Despite these challenges, there has been a lot of success. And we hear more about some of this successes some of us will go on and discuss it.

Olakunle Alonge, MD, MPH, PhD Bloomberg School of Public Health, Johns Hopkins University, USA

Please take some time to review the reading “The Principles of Disease Eradication and Elimination” before proceeding to the poll.

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