The Man Who Made Polio History
Though Salk's IPV is today the recommended vaccine in the United States, it is Sabin's OPV that has been the vaccine of choice during mass campaigns in other countries. It has several advantages:
- Because it is given orally, OPV doesn't require sterile injection equipment or a trained health care worker to administer it.
- It is relatively inexpensive, about 8 U.S. cents per dose.
- It can create "passive immunization" in areas of poor sanitation and hygiene when others come in contact with the feces of recently immunized children.
In its favor, the killed-virus Salk vaccine cannot cause polio, while the live-virus Sabin vaccine can, though it only very rarely does (usually in people with compromised immune systems).
What has kept polio eradication from succeeding at the global level?
Funding is a major issue, especially continuous funding. More than $3 billion has been spent since 1988 on polio eradication, but the Global Polio Eradication Initiative estimates that an additional $200 million is needed for 2006 operations.
"Two or three years back, because of lack of funds, NIDs were discontinued in most African countries that apparently had interrupted transmission," says Ciro de Quadros, director of international programs at the Sabin Vaccine Institute. "However, transmission was still going on in some countries, such as Nigeria. Therefore, when cases from Nigeria were exported to neighboring countries, transmission was again reestablished in those countries."
Civil unrest also has undermined the efforts. In 1995, ceasefires were negotiated in Afghanistan so that more children could be immunized during an NID. In 2001, conflict-ridden central African countries, including Angola and the Democratic Republic of the Congo, pulled together to vaccinate more than 16 million of their children.
In August 2003, rumors that the vaccine caused sterility in girls caused a number of northern states in Nigeria, especially Kano, to suspend immunization efforts. The area subsequently saw a dramatic rise in polio rates in the already endemic country. Worse, 12 neighboring polio-free countries—including Botswana, Chad, and Sudan—were reinfected. In July 2004, immunization programs resumed, but the polio outbreak spread to Yemen, causing 22 cases there. And as recently as May and June 2005, a poliovirus traced genetically to Nigeria infected at least 20 children in Indonesia.
Taken for granted?
Thanks to immunization, two to three generations of children in the developed world have not had to contend with polio and other serious childhood diseases such as measles, whooping cough, and diphtheria. Perhaps for that reason, many of their parents take vaccine-protected health for granted. More worrisome is a small but significant backlash against routine immunization.
"Lack of experience with epidemic disease has led some people to fear the relatively small risks of vaccines more than the larger ones of resurgent epidemics," says author Jane Smith. "Families who decline to vaccinate their children are really relying on the herd effect of general vaccination for protection."
This is a deadly gamble. With global travel and trade becoming more prevalent and affordable, could polio—and perhaps other highly transmittable childhood diseases—return to the Americas?
De Quadros thinks it could.
"Polio is still endemic in parts of Africa and Asia," he says. "Therefore, the countries of the Americas have to maintain very high levels of vaccination coverage and surveillance."
Smith agrees, pointing to Africa as an example. "The rise in polio cases in Africa and other areas where many parents refused vaccination—after almost total eradication—suggests what can happen if larger numbers of children are not vaccinated."
The 50th anniversary of the Salk vaccine is a timely reminder of a past to which no parent or child could want to return.
Sara Francis Fujimura is a freelance writer who lives in Gilbert, Arizona, USA.