Health. Vaccination. What comes to your mind when you hear those words? To me, I believe they are some of the most essential parts of life. Having good health is what allows humans to live their lives to the fullest. Nowadays, being vaccinated is a major aspect of obtaining or maintaining a healthy life. It is one of the reasons why certain diseases, such as tetanus, are rarely seen in the United States. However, it is without a doubt that there are still places in the world that do not have vaccines readily available to them. It is not something that we talk or think about every day because getting vaccinated is normal in the United States. While many of us may not know of anyone who currently has poliomyelitis, it is still present in the world.
Polio Vaccines – Why So Many Acronyms?
Poliomyelitis, or simply known as polio, is a disease caused by an enterovirus from the Picornaviridae family. Moreover, this disease can result in paralysis because it can affect the central nervous system, where it damages the nerves found in the spinal cord. From the information we learned in our microbiology class, the number of distinct strains of the virus that have the ability to cause polio in humans is three. The inactivated polio vaccine (IPV) and the oral polio vaccine (OPV), are two known vaccines that are used. The difference between the two is that IPV contains the virus in its inactivated form, whereas OPV contains the version of the virus that is weak and can be administered orally as well. Both types of vaccines have the ability to induce the formation of antibodies from the immune system. The IPV alone does not prevent the virus from multiplying in the individual, especially in the areas of the intestines and throat. Due to this fact, the IPV does not fully stop this virus from being spread to the feces, and as a result, to other people. On the other hand, the OPV is a better contender to uphold herd immunity because it stops the virus from multiplying and affecting the cells, so that it cannot be spread to other people via feces. It is important to note that there is a big setback to this vaccine – the strain in the vaccine has the ability to mutate and cause disease. Previously, the IPV would be administered and then the OPV. Now, the OPV is not administered in the United States anymore.
The Current State of Polio in the World
According to an article from the Global Polio Eradication Initiative (GPEI), the elimination of the wild poliovirus type 3 (WPV3) had occurred late last year. Previously, the wild poliovirus type 2 (WPV2) was eradicated back in 2015. That’s right – not one, but TWO, of the three strains of polio have been “wiped out of existence”. In addition to that, the World Health Organization (WHO) reported that the wild poliovirus type 1 (WPV1) is still present in Pakistan and Afghanistan. While some people may think that this is not a big deal since the strain is only seen in 2 out of the 195 countries in the world, it still does not get rid of the fact that there are still instances of this disease nowadays.
I believe that it is incredible news that two out of the three strains have been eliminated from the world. In addition, I think it is interesting to note that this fact does not take into account the cases in which the polio was developed from vaccines (or “vaccine-derived”, as many call it). While much celebration is in place, it is important to remember that there are still cases of polio that still exist in the world and that we should continue to keep up the good work. Moreover, we need to remember to give credit to global eradication programs that have demonstrated and continue to be critical components of this.
What Do You Mean “Vaccine-Derived” Polio?
According to an article from NPR, polio continues to be quite a concern in the world, but not in the way that most people think it is. It is not that the WPV3 have made a major comeback into the population. Instead, instances of polio that have resurfaced in countries in Asia and Africa are not necessarily induced by wild polioviruses. Specifically, these cases of polio seem like they are “vaccine-derived”, as most people describe them. A few years back, there was a change made in the OPV, in which only WPV1 and WPV3 were included, while WPV2 was pulled out. This was because the OPV previously still had the WPV2 strain, even though this type of polio was technically eliminated from the world. As mentioned before, the attenuated form of the poliovirus in the OPV has the ability to revert back to its disease-causing self, meaning WPV2 had the potential of coming back again if it stayed in the OPV. However, now Type-2 polio has made a comeback because of the use of vaccines (hence “vaccine-derived”). Moreover, since the attenuated strain for Type-2 polio was taken out, there is no protection against that kind of polio virus anymore. Therefore, to deal with any unplanned instances of WPV2, individuals who had any risk of coming into contact with the virus were given vaccines that only had the ability to prevent Type-2 polio from developing. However, residue from infected areas affected those that did not receive any cautionary vaccination. The strain in this particular vaccine had the ability to change back into its virulent form and infect those that had no protection against Type-2 polio because it was taken out of the OPV years ago.
It seems as if health officials have caught themselves in a spell – how do you get rid of Type-2 polio if it results in the rise of “vaccine-derived” Type-2 polio? Is it too much to simply include the attenuated strain for poliovirus type 2 in the OPV again to make sure that individuals are immune to this form of polio or is it once again too risky? These are the questions that keep me up at night. I believe that better boundaries are needed to prevent the virus from being spread in the environment. This is most definitely a difficult feat to achieve because it is very difficult to contain everything in one place, especially in underdeveloped countries.
Many of us in the United States go to the doctor’s office to receive some type of vaccination and then call it a day. However, we sometimes fail to realize how much attention and research goes into determining the composition of these vaccines. These vaccines were designed to attempt to protect us in the best way possible. Even when it does not, we must try to find alternative solutions to protect ourselves and the rest of the world.
Melanie Nguyen's Microbiology Blog 