Polio Eradication Campaign

views updated

Polio Eradication Campaign

Introduction

Polio, short for poliomyelitis, is a viral disease, which primarily affects children under the age of five. It is highly infectious and can cause rapid paralysis of the limbs and the muscles used in breathing. In the twentieth century, polio began to reach epidemic proportions in the United States and elsewhere. The introduction of an effective vaccine in the 1950s finally began to reduce childhood deaths and disability from polio.

Inspired by the success of the polio vaccine, the World Health Organization (WHO) and its partners launched the Global Polio Eradication Initiative in 1988. The campaign has led to a sharp drop in polio around the world—from around 350,000 cases in 1988 to fewer than 2,000 in the year 2005. Today polio is endemic in only four countries in the world, and the campaign is entering its final phases nearly everywhere. Eradication will prevent more than 10 million polio cases between today and the year 2040.

History and Scientific Foundations

In 1916, an epidemic of polio in the United States claimed around 6,000 lives and paralyzed 27,000 people. When vaccination began in the mid-1950s, there were around 20,000 cases per year. Five years later, the number had dropped to approximately 3,000. In 1979, there were only 10 cases of polio in the United States. Similarly dramatic reductions in polio cases were seen elsewhere.

The World Health Organization (WHO) declared the global eradication of smallpox in 1980. Given the success of the polio vaccine, the announcement of the Global Polio Eradication Initiative by the WHO in 1988 was a natural development. WHO was joined by Rotary International, a worldwide voluntary organization, the U.S. Centers for Disease Control and Prevention (CDC) and UNICEF, the United Nations Children's Fund. Rotary International had been involved in an earlier campaign to eliminate polio from the Americas and was committed to raising funds to protect all children from the disease.

The prime objective of the campaign is to interrupt the transmission of the wild poliovirus by mass vaccination and thereby achieve global eradication of the disease. In doing so, the WHO and its partners hope for the added and long-lasting benefit of strengthening health systems everywhere and promoting routine immunization against other infectious diseases.

The campaign relies upon vaccinating every child, however remote or poorly served by a country's health system. It has made significant progress. In the years since its launch, the number of polio cases has fallen by over 99%—from more than 350,000 in 1988 to 1,951 cases reported in 2005. Polio is now endemic in only four countries in the world—India, Pakistan, Afghanistan, and Nigeria. In 1988, the number of countries where polio was endemic totaled 125.

In 1994, the WHO region of the Americas, comprising 36 countries, was certified polio-free. Then, in 2000, the WHO Western Pacific Region, consisting of 37 countries and areas, including China, followed. In June 2002, the WHO European region, consisting of 51 countries, was finally also declared polio-free.

Two billion children around the world have been vaccinated against polio since the launch of the initiative, with 400 million vaccinations in 2005 alone. It appears that the campaign may now be entering its final phase, with Egypt and Niger having now achieved the goal of successfully interrupting polio transmission. Meanwhile, India and Pakistan are reporting their lowest ever number of cases. Type 3 polio can now be said to be on the verge of eradication in Asia.

However, the task that WHO and its partners set themselves is not yet complete. In parts of northern Nigeria, transmission of poliovirus is uncontrolled, with more than three times as many cases in that country in 2006 as in 2003. There have also been outbreaks in Uttar Pradesh, India, and in Somalia. Such pockets of transmission remain a threat to all. Polio is extremely infectious and it would take only one imported case to reintroduce the disease to a country which had worked to achieved polio-free status.

WORDS TO KNOW

ENDEMIC: Present in a particular area or among a particular group of people.

ERADICATION: The process of destroying or eliminating a microorganism or disease.

MONOVALENT VACCINE: A monovalent vaccine is one that is active against just one strain of a virus, such as the one that is in common use against the poliovirus.

Applications and Research

The polio eradication strategy focuses primarily on high infant immunization coverage with four doses of oral polio vaccine (OPV) during the first year of life. Supplementary doses of OPV should also go to all children under five years in areas where they are especially at risk. Surveillance for the presence of polio infection is a vital part of the campaign. All cases of acute flaccid (floppy) paralysis, which might be polio, need to be reported and subjected to laboratory testing.

Once wild poliovirus transmission is limited to a specific area within a country, a targeted ‘mop up’ campaign is initiated. Ensuring every child is vaccinated can be very challenging. The involvement and commitment of the local community is essential. The main reason why there is still polio in Nigeria is that vaccination was suspended in 2003–2004 because of fears about the safety of the vaccine. Moreover, awareness of the benefits of vaccination may wane in communities where polio is in decline. Therefore, continual efforts to engage local people in the campaign are needed.

The Advisory Committee on Polio Eradication is an independent body that advises the campaign on science and policy. It has recommended the development of new and more effective vaccines to speed up the eradication effort. Therefore, monovalent OPVs are now being employed, and the use of this type of vaccine is set to increase in the coming years. A monovalent vaccine targets only one strain of the virus—polio has three (1, 2, and 3). Monovalent OPV1, against strain 1, was developed in a period of months and used for the first time in India and Egypt in April 2005 and May 2005, respectively.

Monovalent OPV1 was developed specifically for India and Egypt where dense populations and efficient virus transmission were presenting the greatest technical challenge to eradication. It has since been used to deal with outbreaks in Angola, Indonesia, and Yemen. This vaccine, along with its strain 3 equivalent, will likely become the main tool for polio eradication in the future.

Impacts and Issues

To be certified as polio-free, a region must have at least three years of zero polio cases due to wild poliovirus and show that it has a highstandard of surveillance. It must also be able to show it can deal effectively with imported cases of polio. Many countries have achieved this status already, but in a few places, further work is still needed before the goal of polio eradication can be achieved.

At the start of 2006, five states in northern Nigeria accounted for over half of all polio cases worldwide. This is the only place in the world where polio incidence is continuing to rise, despite resumption in vaccination activity in 2004. Meanwhile, the Horn of Africa remains vulnerable, with an epidemic in Somalia having spread outwards from the capital, Mogadishu. It is hard to reach all children in this unstable area with its meager infrastructure, but vaccination is essential if the disease is not to spread to children in neighboring Ethiopia, Sudan, and Kenya.

The work of the Global Polio Eradication Initiative is ongoing and it needs substantial financial support. The money comes from a wide range of governments and organizations around the world. A funding “gap” of 85 million U.S. dollars was identified for 2006 and the shortfall for 2007–2008 is 400 million U.S. dollars, according to the WHO. Polio may seem remote in countries where it has been eradicated, but its continued existence in the world is a threat to all people because of the possibility of imported cases of this very infectious disease.

BIBLIOGRAPHY

Web Sites

Centers for Disease Control and Prevention (CDC). “Pink Book—Poliomyelitis.” <http://www.cdc.gov/nip/publications/pink/polio.pdf> (accessed March 25, 2007).

World Health Organization. “Poliomyelitis.” September 2006. <http://www.who.int/mediacentre/factsheets/fs114/en> (accessed March 25, 2007).

World Health Organization. Global Polio Eradication Initiative. “2005 Annual Report.” May 2006. <http://www.polioeradication.org/content/publications/annualreport2005.asp> (accessed March 25, 2007).

Susan Aldridge

Infectious Diseases: In Context