Toward the end of polio

The international community envisions making polio the second disease, after smallpox, to be successfully eradicated globally. How close is it to reaching this goal?

Polio is now only endemic — or freely circulating and being transmitted — in Nigeria, Afghanistan and Pakistan. That’s down from the more than 125 polio-endemic countries in 1988. India was the latest country removed from the list, with the World Health Organization declaring it officially polio-free in February 2011.

There has also been significant progress in terms of reducing the number of polio cases among children, who are most vulnerable to the disease. At the time polio eradication was adopted as a global goal, more than 350,000 children worldwide were paralyzed or killed by the disease annually. Last year, fewer than 1,500 cases were reported, as per the Bill & Melinda Gates Foundation, a staunch supporter of polio eradication.

Much of this progress is attributed to enhanced global immunization campaigns in the past 23 years. These campaigns are the backbone of eradication efforts because there is no cure for polio and the best way to eliminate it is to protect people, especially children, from getting infected.

There are two major types of polio vaccines: the inactivated polio vaccine, or IPV, and the oral polio vaccine, or OPV.

An injected vaccine developed by Dr. Jonas Salk in 1955, IPV contains killed strains of all three known types of the polio virus. The WHO has certified it as a safe and effective vaccine. IPV, however, is expensive and requires sterile equipment and trained health workers to be administered.

OPV is the cheaper of the two vaccines, and it is also easier to administer. The WHO has certified its effectiveness as well and describes it as “extremely safe.” Developed by Dr. Albert Sabin and licensed for use in 1963, OPV consists of a mixture of live, weakened strains of the three polio virus types. Because of this composition, however, there is a rare risk of paralysis associated with this type of vaccine.

There are also the monovalent OPV, which includes a weakened strain of only one of the three types of poliovirus, and the bivalent OPV, which consists of weakened strains of types 1 and 3 of the virus.

The Global Polio Eradication Initiative — a public-private partnership established in 1988 to lead efforts to banish the infectious disease — uses a combination of these vaccines in their immunization campaigns. The initiative, which is spearheaded by WHO, Rotary International, UNICEF and the U.S. Centers for Disease Control and Prevention, also conducts monitoring activities and leads mop-up campaigns.

Three countries and thousands of people away from its goal of a completely polio-free world, the initiative launched on May 24 an emergency action plan to boost vaccination coverage in Pakistan, Nigeria and Afghanistan. The WHO has also recently declared “the completion of polio eradication to be a programmatic emergency for global public health.”

Read our previous DevTrivia.