Post Polio is a condition that affects up to 80 ∞ of persons who survive paralytic polio; can develop as late as, 30, 40 years after the initial recovery; symptoms vary from mild weakness to severe fatigue and disability .
A: Oral polio vaccine (OPV) contains an attenuated (weakened) vaccine-virus, activating an immune response in the body. When a child is immunized with OPV, the weakened vaccine-virus replicates in the intestine for a limited period, thereby developing immunity by building up antibodies. During this time, the vaccine-virus is also excreted. In areas of inadequate sanitation, this excreted vaccine-virus can spread in the immediate community (and this can offer protection to other children through ‘passive’ immunization), before eventually dying out.
On rare occasions, if a population is seriously under-immunized, an excreted vaccine-virus can continue to circulate for an extended period of time. The longer it is allowed to survive, the more genetic changes it undergoes. In very rare instances, the vaccine-virus can genetically change into a form that can paralyse – this is what is known as a circulating vaccine-derived poliovirus (cVDPV).
It takes a long time for a cVDPV to occur. Generally, the strain will have been allowed to circulate in an un- or under-immunized population for a period of at least 12 months. Circulating VDPVs occur when routine or supplementary immunization activities (SIAs) are poorly conducted and a population is left susceptible to poliovirus, whether from vaccine-derived or wild poliovirus. Hence, the problem is not with the vaccine itself, but low vaccination coverage. If a population is fully immunized, they will be protected against both vaccine-derived and wild polioviruses.
Since 2000, more than 10 billion doses of OPV have been administered to nearly 3 billion children worldwide. As a result, more than 13 million cases of polio have been prevented, and the disease has been reduced by more than 99%. During that time, 24 cVDPV outbreaks occurred in 21 countries, resulting in fewer than 760 VDPV cases.
Until 2015, over 90% of cVDPV cases were due to the type 2 component in OPV. With the transmission of wild poliovirus type 2 already successfully interrupted since 1999, in April 2016 a switch was implemented from trivalent OPV to bivalent OPV in routine immunization programmes. The removal of the type 2 component of OPV is associated with significant public health benefits, including a reduction of the risk of cases of cVDPV2.
The small risk of cVDPVs pales in significance to the tremendous public health benefits associated with OPV. Every year, hundreds of thousands of cases due to wild polio virus are prevented. Well over 10 million cases have been averted since large-scale administration of OPV began 20 years ago.
Circulating VDPVs in the past have been rapidly stopped with 2–3 rounds of high-quality immunization campaigns. The solution is the same for all polio outbreaks: immunize every child several times with the oral vaccine to stop polio transmission, regardless of the origin of the virus.
The World Health Organization formally certified the eradication of wild poliovirus type 3 (WPV3) on World Polio Day. It marks a major victory for global health efforts, including mass vaccination and leaves just one strain of the disease threatening adults and children.
The last known case of WPV3 was confirmed in northern Nigeria in 2012. The WPV2 strain was declared officially eradicated in 2015.
The WHO says the eradication of WPV3 proves that a polio-free world is achievable. Professor David Salisbury, chair of the Global Commission for the Certification of Poliomyelitis Eradication, called for redoubled efforts to eliminate the remaining strain WPV1.
Trust is the key
Polio’s last refuge is in Pakistan and Afghanistan where WPV1 still circulates, in part due to ima lack of trust in immunization campaigns. Misinformation, harmful rumours, armed conflicts and insecurity have all hampered efforts to protect adults and children.
WHO says development efforts are a key component in eradicating infectious diseases.
It estimates that polio eradication efforts have saved the global economy more than $27 billion since 1988. A polio-free world will generate further $14 billion in savings by 2050, compared to the cost countries would incur in controlling the virus.
What is Gavi?
The Global Alliance for Vaccines and Immunisation (Gavi) was launched at the World Economic Forum’s annual meeting in 2000. The global organization brings together public and private sectors with the goal of creating equal access to vaccines for children in the poorest countries.
Gavi has played a leading role in tackling infectious diseases around the world. Last year Gavi-sponsored vaccines immunised 66 million children. Since 2016 Gavi has supported the vaccination of 198 million children worldwide.
Polio (poliomyelitis) mainly affects children under 5 years of age.
1 in 200 infections leads to irreversible paralysis. Among those paralysed, 5% to 10% die when their breathing muscles become immobilized.
Cases due to wild poliovirus have decreased by over 99% since 1988, from an estimated 350 000 cases then, to 33 reported cases in 2018.
As long as a single child remains infected, children in all countries are at risk of contracting polio. Failure to eradicate polio from these last remaining strongholds could result in as many as 200 000 new cases every year, within 10 years, all over the world.
In most countries, the global effort has expanded capacities to tackle other infectious diseases by building effective surveillance and immunization systems.
Polio is a highly infectious disease caused by a virus. It invades the nervous system, and can cause total paralysis in a matter of hours. The virus is transmitted by person-to-person spread mainly through the faecal-oral route or, less frequently, by a common vehicle (for example, contaminated water or food) and multiplies in the intestine. Initial symptoms are fever, fatigue, headache, vomiting, stiffness of the neck and pain in the limbs. 1 in 200 infections leads to irreversible paralysis (usually in the legs). Among those paralysed, 5% to 10% die when their breathing muscles become immobilized.
People most at risk
Polio mainly affects children under 5 years of age.
There is no cure for polio, it can only be prevented. Polio vaccine, given multiple times, can protect a child for life.
Wild poliovirus cases have decreased by over 99% since 1988, from an estimated 350 000 cases in more than 125 endemic countries then, to 33 reported cases in 2018.
Of the 3 strains of wild poliovirus (type 1, type 2, and type 3), wild poliovirus type 2 was eradicated in 1999 and no case of wild poliovirus type 3 has been found since the last reported case in Nigeria in November 2012.
Launch of the Global Polio Eradication Initiative
In 1988, the Forty-first World Health Assembly adopted a resolution for the worldwide eradication of polio. It marked the launch of the Global Polio Eradication Initiative (GPEI), spearheaded by national governments, WHO, Rotary International, the US Centers for Disease Control and Prevention (CDC), UNICEF, and later joined by additional key partners including the Bill & Melinda Gates Foundation and Gavi, the Vaccine Alliance. This followed the certification of the eradication of smallpox in 1980, progress during the 1980s towards elimination of the poliovirus in the Americas, and Rotary International’s commitment to raise funds to protect all children from the disease.
Overall, since the GPEI was launched, the number of cases has fallen by over 99%.
In 1994, the WHO Region of the Americas was certified polio-free, followed by the WHO Western Pacific Region in 2000 and the WHO European Region in June 2002. On 27 March 2014, the WHO South-East Asia Region was certified polio-free, meaning that transmission of wild poliovirus has been interrupted in this bloc of 11 countries stretching from Indonesia to India. This achievement marks a significant leap forward in global eradication, with 80% of the world’s population now living in certified polio-free regions.
More than 18 million people are able to walk today, who would otherwise have been paralysed. An estimated 1.5 million childhood deaths have been prevented, through the systematic administration of vitamin A during polio immunization activities.
Opportunity and risks: an emergency approach
The strategies for polio eradication work when they are fully implemented. This is clearly demonstrated by India’s success in stopping polio in January 2011, in arguably the most technically-challenging place, and polio-free certification of the entire South-East Asia Region of WHO occurred in March 2014.
Failure to implement strategic approaches, however, leads to ongoing transmission of the virus. Endemic transmission of wild poliovirus is continuing to cause cases in border areas of Afghanistan and Pakistan. Failure to stop polio in these last remaining areas could result in as many as 200 000 new cases every year, within 10 years, all over the world. That is why it is critical to ensure polio is eradicated completely, once and for all.
Future benefits of polio eradication
Once polio is eradicated, the world can celebrate the delivery of a major global public good that will benefit all people equally, no matter where they live. Economic modelling has found that the eradication of polio would save at least US$ 40–50 billion, mostly in low-income countries. Most importantly, success will mean that no child will ever again suffer the terrible effects of lifelong polio-paralysis.