World Polio Day: Why do we still need to vaccinate against the disease even after the WHO declared India polio-free in 2014

The World Health Organization (WHO) declared India polio-free in March 2014, three years after the last case of wild polio was reported in 2011. Five years on, we continue to observe National Immunisation Drives against the disease. You might ask: what is the need? And why is the vaccination done so frequently? On World Polio Day today, we answer these questions and a few more about the poliovirus.

A debilitating disease

Polio is an infectious disease caused by the poliovirus. People living with polio have the virus in their intestines. Some of this virus comes out every time they poop, creating further chances of transmission. [caption id=“attachment_7544361” align=“alignleft” width=“380”]  Representational image. Image source: Getty Images.[/caption] There are three subtypes of poliovirus: PV1, 2 and 3. Each one is equally virulent. Even if a child is immune to one of these strains, he or she may still get the infection from the other two serotypes. Regardless of the type, poliovirus targets the nervous system, causing paralysis within a few hours of exposure. The initial symptoms of the disease are fever, headache, fatigue, vomiting and stiffness in neck and limbs. In one in every 200 cases, the child suffers irreversible paralysis, usually in the legs. About 10% of these children get paralysis of breathing muscles and die.

No more polio

In 1988, the WHO started the Global Polio Eradication Initiative (GPEI) to eradicate polio from the world. The initiative is jointly headed by the WHO, national governments, Rotary International, UNICEF and the US Centers for Disease Control and Prevention. Under this programme, India organises the biyearly National Immunisation Days for every child under the age of five. The programme also checks for the presence of poliovirus in the environment - this includes checking of sewage samples across the country. Rotary International instituted 24 October as World Polio Day to celebrate the birth of Jonas Salk, who developed the first-ever polio vaccine in 1952. (Albert Sabin developed the oral polio vaccine a little later in the 1950s.) As of 2013, there is a 99% reduction in polio cases across the globe.

Polio vaccine

There is no cure for polio; which makes prevention all the more important. There are two types of polio vaccine: oral polio vaccine (OPV) and inactivated polio vaccine (IPV). Oral polio vaccine (OPV) contains live but attenuated (weak) poliovirus and is given at the age of six weeks, 10 weeks and 14 weeks with booster doses at 16 months and 24 months of age. OPV is further of two types: trivalent which contains all the three types of poliovirus, and divalent, which contains only two of the three types of poliovirus. As of 2016, most oral polio vaccines are divalent since PV2 poliovirus has been eradicated globally - on 24 October, the WHO announced that PV3 has also been eradicated. IPV is an injectable vaccine that contains dead viruses and is given at six months and 14 months of age on the upper arm. It contains all the three subtypes of poliovirus and is the only way to get children born after 2016 immunised against the type 2 poliovirus.

How many doses does one child need?

A child is usually considered safe from polio after four doses of OPV. However, in hot weather and high-risk areas, such as those with poor sanitation or hygiene, frequent immunisation is important. The WHO recommends getting your child the oral polio dose every time a drive is initiated by the government - till the time the child is five years old. Also, India may have been successful in eradicating polio but the disease remains endemic in certain parts of the world - Afganistan, Pakistan and Nigeria. To keep the virus from being imported from these countries or any other parts of the world, India will have to keep up the immunisation schedule until the disease is completely eradicated from the world. As the National Health Portal of India says: As long as even one child remains infected, children in all countries are at risk of contracting polio. Health articles in Firstpost are written by myUpchar.com, India’s first and biggest resource for verified medical information. At myUpchar, researchers and journalists work with doctors to bring you information on all things health. For more information, please read our article on   Polio: Causes, Symptoms, Prevention and Management_._