April 27, 2021

A success of Prevention: Worldwide Polio Eradication

After a two decade world wide effort, POLIO is almost eradicated
5 minutes to read without links

Poliomyelitis was the most worrying childhood disease and could be prevented by vaccination

Polio either killed the patients or left them disabled for the rest of their life

Poliomyelitis, short Polio, is caused by an infection through the gut with the polio-virus, which exists in three strains. In about 0.5% of the cases the virus moves into the central nervous system and causes muscle weakness resulting in flaccid paralysis. Many people fully recover, however in those with muscle weakness about 2-5% of the children and 15-30% of the adults die. The polio-virus is usually spread from person to person through infected fecal matter entering the mouth, which includes consumption of infected food or water. Once infected, there is no treatment. In the 20st century it became the one of the most worrying childhood diseases in Europe and the United States.

The disease and its spread can be prevented by vaccination and the first vaccines were developed in the 1950-ies. There are two types of vaccines: The Injected polio vaccine (IPV), developed by Jonas Salk, 1952,which contains trivalent inactivated virus, that is injected. It is very effective against all three strains; vaccinated individuals do not get sick, but they may still contain the virus in their intestines and thus spread the virus. Furthermore, vaccination requires medically trained personal. The oral polio vaccine (OPV) developed shortly later by Albert Sabin 1957, which is an attenuated virus that replicates efficiently in the gut, the primary site of the wild polio infection and replication, but is unable to replicate within the nervous system. It requires 3 applications of a few drops of vaccine directly into the oral cavity or via with a sugar cube to reach 95% protection of the individual. Since it is excreted via feces as well, it can protect unvaccinated individuals in areas where polio is endemic. This is called contact immunity and helps to limit the spread of the virus. The down side of this is that in very seldom cases mutants of this virus, called vaccine derived polio-virus strains may be able to induce the disease. Due to its high efficiency and simplicity of application the OPV became the vaccine of choice. It was expected that with mass vaccinations https://www.webmd.com/lung/what-is-herd-immunity#1) could be accomplished.

Application of OPV

In 1988, the World Health Organization (WHO, https://en.wikipedia.org/wiki/World_Health_Organization), together with Rotary International, UNICEF (https://en.wikipedia.org/wiki/UNICEF), and the U.S. Centers for Disease Control and Prevention (CDC, https://en.wikipedia.org/wiki/Centers_for_Disease_Control_and_Prevention) passed the Global Polio Eradication Initiative(GPEI), with the goal of eradicating polio by the year 2000. The initiative was inspired by Rotary International's 1985 pledge to raise $120 million toward immunizing all of the world's children against the disease.

Decrease of polio cases worldwide

A worldwide vaccination campaign with a reporting system and elaborated analysis techniques started, and year after year the successes could be reported. The Americas were declared polio-free in 1994. The last polio case in Europe was reported in 1998 and the WHO declared Europe polio-free in 2002. By 2001 575 million children (almost 1/10 of the world population) had received some two billion of OPV doses.

The health care workers had to surmount a plethora of obstacles, such as the quality of the local health care system, the fact that most polio infected had very little or no symptoms, but were spreading the disease, as well as with smallpox eradication, false rumors and religious objections as well as wars made the task almost impossible. In 2006 polio was found endemic in only 4 countries in the world, but then there were some setbacks. Therefore in 2013 the WHO freed substantial funds to continue the program and by 2020 Africa was declared polio-free.Today there are a few wild cases in Afghanistan and Pakistan.

We are almost there.

Source: https://en.wikipedia.org/wiki/Polio_eradication


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