One case and minimal indications of further transmission may not seem noteworthy, yet the majority of Americans are immune to paralysis due to widespread polio vaccination in the country.
More than 92% of children in the United States have had polio vaccinations by the age of 2, according to the most recent statistics from the U.S. Centers for Disease Control and Prevention.
Poliovirus spreads from the human intestinal tract via the fecal-oral route: a person gets stool germs on their hands, touches something, or shakes hands with another person, and that person puts their contaminated hands in their nose or mouth. Vaccinated people are not at risk if they contract poliovirus. Because of this, young children who are still in diapers are particularly prone to infection.
When poliovirus infects gut cells, it might result in cramping, diarrhea, or constipation, which are all moderate illnesses. However, on rare occasions, the virus can cross the intestinal barrier and enter the bloodstream, where it can then target the motor neurons in the spinal cord, which are the cells that instruct muscles to contract. These cells are destroyed when the virus attacks them, leaving victims paralyzed for the rest of their lives.
According to medical professionals, there are 300 to 1,000 mild infections for every paralytic polio case.
Until the year 2000, Americans were immunized against polio with two types of vaccines: vaccine drops, sometimes given on sugar cubes, made with live, weakened poliovirus, and an injected vaccine made with killed polio virus.
There are several key differences between the vaccines, but one major difference is that the oral vaccine induces mucosal immunity, which means that if a vaccinated person comes into contact with poliovirus again, it will not be able to replicate in their gut and will not be passed on to someone else. However, there is a disadvantage to using the oral vaccine. The main disadvantage of the oral polio vaccine is that you shed it.
The weakened virus in the oral vaccine can escape the gut and cause paralysis very rarely, about once every 3 million doses. The weakened virus can also be shed in the stool, and on rare occasions, it will mutate and revert to a form of the virus that can cause paralysis, especially if the virus is spread in areas with poor sanitation and low vaccination rates.
The vaccine, which is administered intravenously and makes use of the dead virus, is immutable. The injectable vaccine is even safer than the relatively safe oral vaccine.
