India to try more effective vaccine bOPV to eradicate polio

India plans to introduce more targeted police vaccine in certain areas of the country instead of the currently used general polio vaccine as part of its nationwide campaign to eradicate polio from the country.

The health ministry under government of India has decided to use bivalent Oral Polio Vaccine (bOPV) as this is found more efficacious to drive out the virus from certain pockets of the country where polio still lurks.

bOPV vaccine is found to be more efficacious than the traditionally used tOPV in clinical trials conducted in India.

Incidence of polio cases in Western UP and some parts of Bihar continues to place India as the second most afflicted nation in the world, after Nigeria, even though the disease has come down drastically in other parts of the country.

Besides, bOPV has been shown as good as the currently used monovalent oral polio vaccines mOPV1 and mOPV3 – which protect against the corresponding poliovirus type, pointed out
India Expert Advisory Group (IEAG), the advisory body to the government of India on polio eradication.

The use of the bivalent OPV is expected to achieve interruption of transmission of polio type-1 while maintaining control of polio type-3 and once this is achieved, the strategy will shift to interruption of polio type-3.

The geographic scope of both poliovirus type-1 and type-3 has reduced further, even though the number of polio cases has increased in 2009 as compared to 2008,.

India ranked second in the case of polio cases last year, behind Nigeria which recorded 798 cases, according to the latest statistics with the WHO monitoring cell.

This year, up to July 31, India reported 206 cases whereas Nigeria had 363 cases. Pakistan is standing way down on the third spot with 31 cases.

India continues to be among the only remaining five reservoir of polio virus in the world, despite decades of intensive preventive programmes against the disease. Of the total 1,315 cases of poliomyelitis reported worldwide in the year 2007, over 60% of cases (874) occurred in India

Most recently two more new cases were reported both WPV3 cases from Moradabad, Uttar Pradesh (UP). However, the total number of polio cases for 2009 have come down to 21, so far, compared to 165 cases at this time last year.

Poliomyelitis (polio) is a highly infectious disease caused by a virus. It affects the nervous system, and can cause total paralysis in a matter of hours. It can strike at any age, but affects mainly children under three (over 50% of all cases).

The virus enters the body through the mouth and multiplies in the intestine. Initial symptoms are fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs. One in 200 infections leads to irreversible paralysis (usually in the legs).

Amongst those paralysed, 5%-10% die when their breathing muscles become immobilized. Although polio paralysis is the most visible sign of polio infection, fewer than 1% of polio infections ever result in paralysis.

Poliovirus can spread widely before cases of paralysis are seen.  After initial infection with poliovirus, the virus is shed intermittently in faeces (excrement) for several weeks. During that time, polio can spread rapidly through the community.

In the remaining polio endemic countries, poliovirus is mainly passed through person-to-person contact. Most people infected with the poliovirus do not develop polio paralysis or other symptoms of polio infection. However one in 200 people do have symptoms and can become paralyzed. The virus enters the environment through faeces of people infected then is passed to others especially in situations of poor hygiene. The poliovirus can also infect persons who have been vaccinated and can be carried by them. Such individuals will not develop polio, but can carry the virus in their intestines and can pass it to others in conditions of sub-standard hygiene. The disease may infect thousands of people, depending on the level of sanitation, before the first case of polio paralysis emerges. Individuals can carry the virus in their intestines just long enough to transmit to others.

WHO considers a single confirmed case of polio paralysis to be evidence of an epidemic – particularly in countries where very few cases occur.
How can polio be prevented?

There is no cure for polio, it can only be prevented through immunization. Polio vaccine, given multiple times, almost always protects a child for life.

Oral polio vaccine (OPV) is highly effective and inexpensive (about 5 per dose, or Rs 1.5 per child.) A study carried out in an isolated Eskimo village showed that antibodies produced from subclinical wild virus infection persisted for at least 40 years. Because the immune response to oral polio vaccine is very similar to natural polio infection, it is expected that oral polio vaccination provides similar lifelong immunity to the virus.
Polio paralysis

Once established in the intestines, poliovirus can enter the blood stream and invade the central nervous system – spreading along nerve fibres. As it multiplies, the virus destroys nerve cells (motor neurons) which activate muscles. These nerve cells cannot be regenerated and the affected muscles no longer function. The muscles of the legs are affected more often than the arm muscles. The limb becomes floppy and lifeless – a condition known as acute flaccid paralysis (AFP). 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.
WHO’s polio eradication goals

In May 1988, the World Health Assembly committed the member nations of the World Health Organization (WHO) to achieve the goal of eradication of poliomyelitis virus from the face of earth. The key targets of the goal were:

* no cases of clinical poliomyelitis associated with wild poliovirus
* no wild poliovirus found worldwide despite intensive efforts to do so.

Following a concerted effort,  the Americas (last case in 1991, Peru; Region certified polio-free in 1994), the Western Pacific Region (last case in 1997, Cambodia; Region certified 2000), and the European Region (last case in 1998, Turkey; Region certified 2001), were certified polio-free by WHO.

In 1988, the Government of India  committed the nation to the goal of  global polio eradication. Since 1995, the Ministry of Health and Family Welfare, Government of India has been conducting immunization and surveillance activities aimed at the complete elimination of poliovirus and paralytic polio for the country.
Polio vaccination in India

In India, vaccination against polio was initiated in 1978 under Expanded Programme on Immunization (EPI) and the coverage achieved by 1984 was around 40% of all infants with 3 doses of Oral Polio Vaccine (OPV). In 1985 the Universal Immunization Programme (UIP) was launched and implemented in phased manner to cover all districts in the country by 1989-90. During 1986 the UIP was accorded the status of a Technology Mission under the banner of the Technology Mission on Immunization.

This resulted in significant increase in coverage to over 95% during 1990-91 and is being sustained over 90% since then. The number of  reported cases of polio declined from 28757 during 1987 to 3265 in 1995.

At this stage, in pursuance to the World Health Assembly Resolution of 1988, in addition to administration of routine OPV through the Universal Immunization Program, the Pulse Polio Immunization (PPI) Programme was launched in 1995-96 to cover all children below the age of 3 years. In order to accelerate the pace of polio eradication, the target age group was increased from 1996-97 to all children under the age of 5 years. This resulted in further decline in number of polio cases to 1005 reported during 1996.

Earlier, as the country continued to struggle with spurt in the cases of polio outbreaks, the government had approved Rs 3203 crore for the eradication of polio for the next three years from the current financial year. The main objective of the project is to achieve the goal of zero transmission of polio and obtaining international polio free certification. For accomplishment of this goal, the annual strategy for polio eradication is decided on the basis of the recommendations of the IEAG consisting of national and international experts.