Context: Recently, the World Health Organisation (WHO) has declared Africa free of polio after an announcement from the Africa Regional Certification Commission (ARCC) for Polio Eradication.
Background

• It was endemic around the world until a vaccine was found in the 1950s, though this remained out of reach for many poorer countries in Asia and Africa.
• In 1988, when the WHO, UNICEF and Rotary launched the worldwide campaign to eradicate the disease, there were 350,000 cases globally. In 1996, there were more than 70,000 cases in Africa alone.

Current Scenario

• The milestone comes four years after Nigeria - the last polio-endemic country in Africa - recorded its final case of wild poliovirus.
• "With this announcement, five out of the six World Health Organization (WHO) regions are now wild polio-free, serving as much-needed encouragement for the hundreds of thousands of frontline health workers;
• Who have been fighting tirelessly to keep children worldwide safe and immunized against polio and other vaccine-preventable diseases, even in the midst of the COVID-19 pandemic."
• Note: WHO’s six regional groups: African Region, Region of the Americas, South-East Asia Region, European Region, Eastern Mediterranean Region, and Western Pacific Region. India is a member state of the South East Asia Region at the WHO.
• While many African countries haven't had a case of wild polio in years, since 1996, eradication efforts "have prevented up to 1.8 million children from crippling life-long paralysis and saved approximately 180,000 lives.
• Poliomyelitis: the medical term for polio - is an acutely infectious and contagious virus which attacks the spinal cord and causes irreversible paralysis in children.
• Thanks to a global effort and financial backing - some US$19 billion over 30 years - only Afghanistan and Pakistan have recorded cases this year: 87 in total.

About Polio virus

• It is a disease caused by three different strains of poliovirus, which sometimes attacks nerve cells in the spinal cord and causes partial or complete paralysis.
• The person can be infected from poliovirus through contact with the feces of an infected person, or through contaminated food, water and objects that come in contact with the mouth.
• It is a rare form of the virus that mutates from the oral polio vaccine and can then spread to under-immunised communities.

There are two types of vaccines to prevent infection.

• OPV (Oral Polio Vaccine): It is given orally as a birth dose for institutional deliveries, then primary three doses at 6, 10 & 14 weeks and one booster dose at 16-24 months of age.
• Injectable Polio Vaccine (IPV): It is introduced as an additional dose along with the 3rd dose of DPT under the universal immunization programme (UIP).

About Vaccine-derived Polio-virus

• It is a strain of the weakened poliovirus that was initially included in oral polio vaccine (OPV) and that has changed over time and behaves more like the wild or naturally occurring virus.
• This means it can be spread more easily to people who are unvaccinated against polio and who come in contact with the stool or respiratory secretions, such as from a sneeze, of an infected person. These viruses may cause illness, including paralysis.

How is it spread?

• 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.

What’s the issue here?

• A circulating vaccine-derived poliovirus (cVDPV) 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.

Additional Information

• In 2014, India and the entire WHO South-East Asia Region were officially declared as being polio-free.
• India uses oral polio vaccine (OPV) in its immunisation programme.

Global Polio Eradication Initiative (GPEI)

• It is a public-private partnership established in 1998.
• It is led by national governments with six core partners i.e. the World Health Organization (WHO), Rotary International, the US Centers for Disease Control and Prevention (CDC), the United Nations Children’s Fund (UNICEF), the Bill & Melinda Gates Foundation and Gavi, the Vaccine Alliance.
• Its goal is to eradicate polio worldwide.
• It was described by the World Health Organization as the largest public health initiative in history.