- Raúl Rivas González
- The Conversation*
Since 1988, polio cases have fallen by 99.9%, but the disease remains a public health emergency of international concern.
Polio is an ogre that frightened the world during the 20th century, but successful vaccination campaigns have caused the disease to be besieged, persecuted and cornered in such a way that it is currently endemic in just two countries: Afghanistan and Pakistan.
The Global Polio Eradication Initiative (GPEI) has launched a new strategic plan for the period 2022-2026 that aims to interrupt all polio transmission in Afghanistan and Pakistan by the end of 2023.
Evolution and effects of polio
Until the end of the 19th century and the beginning of the 20th century, polio behaved as a sporadic disease that mainly affected children.
Everything changed in the early 20th century, when polio outbreaks gradually grew around the world.
In 1916, the United States suffered a huge polio epidemic which was one of the first major public health crises.
The states of Massachusetts, New York, New Jersey, and Connecticut had very high numbers of infections.
Across the country, more than 23,000 infected people and more than 5,000 deaths from the disease were documented.
That 1916 epidemic turned out to be the first of the many outbreaks that emerged in the following years.
The causative agent of polio is a human enterovirus, poliovirus.
Polioviruses are highly contagious RNA viruses.
There are three poliovirus serotypes (VP1, VP2, and VP3).
VP2 was last isolated in India in 1999 so it is considered removed from nature.
In Afghanistan and Pakistan only wild type 1 and type 3 polioviruses that cause paralytic polio continue to circulate.
Serotype 1 is the most widespread.
The Polio is insidious and harmful.
Although most people recovered quickly, many suffer temporary or permanent paralysis and a significant number die.
The infection is usually asymptomatic, in 95% of the cases, or it presents with asthenia, anorexia and general malaise.
However, in 0.1% of cases the disease progresses to the paralytic spinal form.
Before starting vaccination, the prognosis of the paralytic form associated a mortality of 5-10% which rose to 20-60% in cases with bulbar involvement.
Two-thirds of patients with paralysis they were left with sequels.
When the GPEI set out to eradicate polio from the planet in 1988, an estimated 350,000 children worldwide were paralyzed by polio each year.
There are two types of vaccines: the attenuated (Sabin), which is no longer used in countries such as Spain, and the inactivated (Salk), which is currently used and recommended.
The inactivated polio vaccine (VPI) is part of the pentavalent vaccines (diphtheria, tetanus, pertussis and Haemophilus influenzae type b) and of the hexavalent vaccines (diphtheria, tetanus, pertussis, Haemophilus influenzae type b and hepatitis B).
Also of the Tdpa-VPI vaccine (tetanus, diphtheria, acellular pertussis and polio).
IPV includes all three types of poliovirus and with only 4 doses of vaccine it is considered that the protection level is close to 100% and very durable.
Oral Polio Vaccine (OPV) contains an attenuated vaccine virus that activates an immune response in the body.
In rare cases, when the population is markedly under-immunized, vaccine viruses (being attenuated viruses) can undergo genetic changes that give them the ability to produce paralysis, thus creating the so-called circulating vaccine-derived polioviruses (cVDPV).
The low risk associated with circulating vaccine-derived polioviruses is hardly significant compared to Huge Benefits of Oral Polio Vaccine to public health, preventing hundreds of thousands of cases of wild poliovirus polio annually.
As of 2015, more than 90% of cVDPV cases were due to the type 2 component of OPV.
Transmission of wild type 2 poliovirus was interrupted since 1999, and in April 2016 the trivalent IPO was changed to the bivalent IPO.
The polio vaccine was one of the first universal childhood vaccinations which was introduced in Spain, first in school campaigns 50 years ago and later in the stable calendar.
Since 2000, more than 10 billion doses of oral polio vaccine have been administered to nearly 3 billion children worldwide.
Thanks to this, more than 13 million cases have been prevented and the disease has been reduced by 99%.
What can happen now in Afghanistan?
Unfortunately, the polio virus may have found an unexpected ally.
With the withdrawal of US troops and the fall of the Afghan regime, the Taliban forces have assumed control of the country.
For the past three years, the Taliban have blocked house-to-house polio vaccination in areas that were under their rule, putting 3 million children out of the reach of the vaccination campaign and, therefore, exposing them to the disease and making it easier for the virus to continue in circulation.
At the beginning of June 2021, five health workers carrying out a vaccination campaign against polio in the Afghan province of Nangarhar died during a series of targeted extremist attacks.
This caused the activity that was intended to protect the virus from the virus to be suspended. more than 10 million children under five years old.
Dr. Ramiz Alakbarov, the UN resident humanitarian coordinator in the country, said he was dismayed by the brutality of these murders and that senseless violence it must cease.
Unfortunately, the future prospects for combating polio in Afghanistan are terrifying.
Until now, 85% of all polio cases occurred in inaccessible areas due to Taliban control.
Now that Taliban control will be total, what will happen?
What’s more, the covid-19 pandemic the situation worsens.
The present is uncertain and the future threatening.
Afghanistan and Pakistan share 2,670 kilometers of border and the virus does not need a visa to travel.
There is a window of hope because the Taliban recently gave the green light to the GPEI to carry out vaccination in mosques in the provinces where house-to-house vaccinations were banned for fear that local people would pass on information that would help the United States to attack the Taliban regime.
Let us hope that international mediation will make it easier for the Taliban leaders not to oppose vaccination campaigns, because depriving children of the guarantee of a healthy life is inhumane.
* Raúl Rivas González is Professor of Microbiology at the University of Salamanca, Spain.
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Eddie is an Australian news reporter with over 9 years in the industry and has published on Forbes and tech crunch.