Type-2 polio virus contamination detected in the vials used for immunisation in Uttar Pradesh, Maharashtra and Telangana

What is poliomyelitis/polio?

• Poliomyelitis, often called polio or infantile paralysis is an acute infectious disease caused by polio virus. The virus is a human enterovirus of the Picornaviridae
• There are three types of Polio Virus: 1,2,3-Single stranded RNA virus Natural or Wild Polio Virus (WPVS).
• It is transmitted from one person to another by oral contact with secretions or faecal material from an infected person. It attacks the central nervous system through the blood stream and damage the cells and paralyse the victim

Types of Polio vaccines

Two different kinds of vaccine are available: an inactivated (killed) polio vaccine (IPV) and a live attenuated oral polio vaccine (OPV).

Inactivated Polio vaccine (IPV):

• It was first introduced in 1995 by Dr. Jonas Salk
• It is produced from wild-type poliovirus strains of each serotype that have been inactivated (killed) with formalin.
• It is an injectionable vaccine and can be administered alone or in combination with other vaccines (e.g., diphtheria, tetanus, pertussis, hepatitis B, and haemophilus influenza).

Oral Polio vaccine (OPV):

• It was first introduced in 1961 by Dr. Albert Sabin
• consists of a mixture of the three live attenuated poliovirus serotypes (Sabin types 1, 2 and 3), selected for their lower neurovirulence and reduced transmissibility.
• Apart from trivalent OPV (tOPV), monovalent OPVs viz. against Type 1 (mOPV1) and against type-3 (mOPV3) have been licensed for use in some countries
• In 2009, 2 bivalents (type-1 and type-3) OPVs (bOPVs) were licensed.

Note: Worldwide, the second strain was withdrawn from vaccines on confirmation that it had been eradicated among humans

• In some rare cases, OPV can lead to vaccine-associated paralytic polio (VAPP) or vaccine-derived poliovirus (VDPV)

Global status of Polio

• Since 1988, polio has been eliminated in 122 countries. Only Pakistan, Afghanistan and Nigeria remained endemic (as of 2014)
• However, new wild type 1 cases have recently appeared in the previously polio-free countries of Syria, Iraq, Cameroon, Equatorial Guinea, Ethiopia and Somalia.
• Remaining cases of wild polioare type 1. Wild type 2 polio appeared to have been completely eradicated (the last naturally acquired case was in 1999). Transmission of wild type 3 polio is believed to have been stopped.
• The World Health Organization certifies polio elimination on a regional basis, and has certified the following regions free of wild polio:
• Region of the Americas (1994);
• Western Pacific Region (2000);
• European Region (2002);
• South-East Asia Region (2014) 

Status of Polio in India

• In 2009, India reported 741 polio cases, more than any other country in the world, according to the Global Polio Eradication Initiative.
• The last case was reported from West Bengal in 2011 which was Type-1 Polio Virus
• India attained Polio Free status in 2014 after successfully eliminating wild P1 and P3 strains
• Last case of Wild Polio Virus Type 2 in India was reported in 1999.
• India eliminated the type-2 strain in 2016, and the type-2 containing poliovirus vaccine (ToPV) was phased out in April 2016.

Initiatives taken in India to eradicate polio:

• 1988: India committed to resolution passed by World Health Assembly for global polio eradication. WHO launched the Global Polio Eradication initiative
• 1995: National Immunization Day (NID) commonly known as Pulse Polio Immunization programme was launched and is conducted twice in early part of each year. Additionally, multiple rounds (at least two) of sub national immunization day (SNID) are conducted over the years in high risk states/areas.
• 1997: The National Polio Surveillance Project (NPSP) is established for poliovirus surveillance. It is a collaboration between GoI and World Health Organization (WHO)
• 2015: India introduced IPV routine immunization as part of Polio Eradication and Endgame Strategic plan.

Note: In 2012, the World Health Assembly endorsed the Polio Eradication & Endgame Strategic Plan 2013-2018, calling on countries to strengthen routine immunization programmes and introduce at least one dose of IPV in countries OPV

Other Steps taken

• Intensive efforts are undertaken to improve routine immunization coverage that involves administering polio vaccines, in addition to other vaccines, to infants under the Universal Immunization Programme (UIP).
• All States and Union Territories in the country have developed a Rapid Response Team (RRT) to respond to any polio outbreak in the country.
• Emergency Preparedness and Response Plans (EPRP) has been developed by all States indicating steps to be undertaken in case of detection of a polio case.
• To reduce risk of importation from neighbouring countries, international border vaccination is being provided through continuous vaccination teams (CVT) to all eligible children
• Guidelines have been issued by the government for mandatory requirement of polio vaccination to all international travellers for travel to India and other affected countries: Afghanistan, Nigeria, Pakistan, Ethiopia, Kenya, Somalia Syria and Cameroon.

Challenges

1. Concerns over VAPP: Despite higher risks of VAPP and VDPV, OPV has been preferred over IPV for public health programs during pre-eradication period, mainly due to its lower costs and ease of implementation. However, the continued use of OPV has risen concerns over VAPP related cases and virus transmission to unvaccinated children.
2. Poor Environmental Sanitation: High prevalence of non-polio enteroviruses and poor environmental sanitation at many places is a major concern as it makes OPV less effective.
3. Low coverage: The coverage for IPV in India is still low, making a large number of children vulnerable to Type-2 virus

The recent crisis:

• Some batches of oral polio vaccine, manufactured by Biomed, have been found to be contaminated with polio type 2 virus. The contamination is a serious concern as it endangers many people who have not IPV and are exposed to strain 2 making them vulnerable to VAPP.
• The issue also highlights faulty testing by Central Drugs Laboratory. CDL tested vaccines only for the viruses mentioned on the label i.e. only P1 and P3 on the assumption that what the manufacturer has mentioned on the label is accurate.

Way ahead:

1. India’s efforts to polio eradication is commendable. It has a robust polio surveillance programme, which needs to be continued. Such strong vaccination and surveillance programme should be adopted for other preventable diseases too.
2. The government should ensure universal coverage of IPV as they are essential for post wild-type polio virus eradication, to get rid of VDPV and VAPP. Further, it is important to ensure monitoring of VAPP cases in India, to establish that use of a single dose of IPV followed by immunisation using bivalent OPV has led to a reduction in the number of VAPP cases.
3. As government thrives to permanently launch the injectable IPV all over the country, it will require money and trained manpower. Thus, it is important to ensure adequate funding and human resource
4. Clean, safe drinking water and good sanitation are key to fighting the spread of polio and making polio eradication programmes. Thus, it is of utmost importance to improve sanitation and hygiene conditions in the country