Polio: A History and a Hope

Previously:

So let’s talk about polio. For those of you who don’t know what it is, or who only know of it because you know our 32nd president, Franklin D. Roosevelt, had it, poliomyelitis is a virus that enters the body orally, infects the cells that line the throat and intestinal tract, then invades the bloodstream and nerve cells. Because of this, the signs and symptoms of polio include headache, fever, stiff neck, nausea, pain, and muscle spasms. It can also lead to paralysis. For poliomyelitis, there are three serotypes, or groups of strains with a specific antigenic structure, and two different types of vaccines to protect against it. The IPV, otherwise known as the Salk vaccine, was developed in the 1950s and protects against all three serotypes using inactivated virus. The OPV, known as the Sabin vaccine, is an oral vaccine that was developed in 1961 and has attenuated strains of the virus that can replicate the cells that line the throat and intestinal tract, causing a mucous response and mucosal immunity. Because of this, the OPV is considered to provide better herd immunity, as it can fight the virus as soon as it enters our system, rather than later on when we’ve had more time to spread the virus. It is also cheaper. However, the attenuated viruses can also mutate and become virulent. And the downside to IPV is that it doesn’t produce the mucosal immunity, so it can still be easily spread to others. In order to create the most effective method of preventing Polio, the United States adopted a strategy of using both vaccines, the IPV first to protect the child being immunized, then the OPV to boost the child’s mucosal immunity and herd immunity. This worked because by 1979 the United States was free of wild-type polio, and it had been eliminated in the western hemisphere by 1991.

Now:

As of 2015, the second serotype of Poliomyelitis was declared globally eradicated. We now use an OPV that has only the serotypes 1 and 3! And the United States has been completely polio free for approximately 27 years! However, in some parts of the world, Polio is still an issue. For example, in many countries that are not yet free of Poliomyelitis, it is not because they aren’t vaccinated but because there are few cases of the attenuated OPV mutating and becoming virulent. One of the latest solutions to this issue is a new oral polio vaccine, called the nOPV2, is being researched. Scientists have located which part of the virus’ genome in which most of the mutations that make it virulent occur, and have edited eighteen nucleotides at that part of the genome to hopefully prevent the virus from mutating and becoming virulent again. This vaccine is currently still under testing, but if it works it could be a key player in preventing vaccine-derived polio and finally eradicating polio from our planet.

However, in order for us to completely eradicate the virus, we must remember how we have gotten this close to begin with. We need to continue vaccinating against it so that everyone has immunity and our herd immunity is high. If we stop vaccinating against it, it could leave room for the virus to begin to reoccur in areas of the world that have already eradicated it. We must continue to vaccinate, even if there is a risk of vaccine-derived polio, because the eventual goal of eradicating polio altogether is much more important for the world’s health and future. And if we can eliminate vaccine-derived polio, as we may be on the verge of doing, we are one big step closer to our end goal.

If you have any questions about who should be vaccinated and when they should be vaccinated, visit the CDC Polio vaccination site or talk to your doctor or child’s pediatrician for more information. People who should receive the vaccine include includes infants, toddlers, preschoolers, older children who have not yet received the vaccine, or adults who are at an increased risk due to potential exposure.