Context: The West Bengal government announced that it was introducing an additional dose of injectable polio vaccine as part of the Universal Immunisation Programme (UIP) for children.
What is polio?
- Poliomyelitis is a crippling disease that results from infection with any one of the three related poliovirus types (referred to as types P1, P2, and P3), members of the enterovirus (picornavirus) family.
- Poliovirus is transmitted from one person to another by oral contact with secretions or faecal material from an infected person.
- Once viral reproduction is established in the mucosal surfaces of the nasopharynx, poliovirus can multiply in specialized cells in the intestines and enter the blood stream to invade the central nervous system, where it spreads along nerve fibres. When it multiplies in the nervous system, the virus can destroy nerve cells (motor neurons) which activate skeletal muscles. These nerve cells cannot regenerate, and the affected muscles lose their function due to a lack of nervous enervation – a condition known as acute flaccid paralysis (AFP).
- Typically, in patients with poliomyelitis muscles of the legs are affected more often than the arm muscles. More extensive paralysis, involving the trunk and muscles of the thorax and abdomen, can result in quadriplegia.
- In the most severe cases (bulbar polio), poliovirus attacks the motor neurons of the brain stem – reducing breathing capacity and causing difficulty in swallowing and speaking. Without respiratory support, bulbar polio can result in death. It can strike at any age, but affects mainly children under three (over 50% of all cases).
Types of Polio vaccine
- There is no cure for polio, but there are safe, effective vaccines which, given multiple times, protect a child for life. Two different kinds of vaccine are available:
- An inactivated (killed) polio vaccine (IPV) developed by Dr. Jonas Salk and first used in 1955, and
- A live attenuated (weakened) oral polio vaccine (OPV) developed by Dr. Albert Sabin and first used in 1961.
Inactivated (killed) polio vaccine
- IPV is produced from wild-type poliovirus strains of each serotype that have been inactivated (killed) with formalin. As an injectable vaccine, it can be administered alone or in combination with other vaccines (e.g., diphtheria, tetanus, pertussis, hepatitis B, and haemophilus influenza). IPV provides serum immunity to all three types of poliovirus, resulting in protection against paralytic poliomyelitis.
Oral Polio vaccine
- OPV consists of a mixture of live attenuated poliovirus strains of each of the three serotypes, selected by their ability to mimic the immune response following infection with wild polioviruses, but with a significantly reduced incidence of spreading to the central nervous system. OPV strains also produce a local immune response in the lining (‘mucous membrane’) of the intestines – the primary site for poliovirus multiplication.
Polio eradication efforts in India
- Pulse Polio is an immunization campaign established by the government of India to eliminate poliomyelitis (polio) in India by vaccinating all children under the age of five years against the polio virus. The project fights polio through a large-scale, pulse vaccination programme and monitoring for poliomyelitis cases.
- In India, vaccination against polio started in around 1972 with Expanded Programme on Immunization (EPI). By 1999, it covered around 60% of infants, giving three doses of OPV to each.
- In 1985, the Universal Immunization Programme (UIP) was launched to cover all the districts of the country. UIP became a part of child survival and safe motherhood program (CSSM) in 1992 and Reproductive and Child Health Program (RCH) in 1997 . This program led to a significant increase in coverage, up to 5%. The number of reported cases of polio also declined from thousands during 1987 to 42 in 2010.
- In 1995, following the Global Polio Eradication Initiative of the World Health Organization (1988), India launched Pulse Polio immunization program with Universal Immunization Program which aimed at 100% coverage.
- The last reported cases of wild polio in India were in West Bengal and Gujarat on 13 January 2011. On 27 March 2014, the World Health Organization (WHO) declared India a polio free country, since no cases of wild polio been reported in for five years
Universal Immunisation Programme (UIP)
- Universal Immunisation Programme (UIP) is a vaccination programme launched by the Government of India in 1985. It became a part of Child Survival and Safe Motherhood Programme in 1992 and is currently one of the key areas under the National Rural Health Mission since 2005.
- The programme now consists of vaccination for 12 diseases- tuberculosis, diphtheria, pertussis (whooping cough), tetanus, poliomyelitis, measles, hepatitis B, diarrhoea, Japanese encephalitis, rubella, pneumonia (haemophilus influenzae type B) and Pneumococcal diseases (pneumococcal pneumonia and meningitis). Hepatitis B and Pneumococcal diseases were added to the UIP in 2007 and 2017 respectively.