31 October 2010
A new polio vaccine gives hopes that the disease can be completely eradicated. Polio can cause severe deformities and paralysis in children. The number of polio cases worldwide has dropped by over 99 percent in recent years because of a global vaccination campaign started in the 1950s. But the disease still threatens children in at least four countries in Africa and South Asia. Now, clinical trials in two countries have confirmed the effectiveness of a new vaccine. And the World Health Organization says complete eradication of polio could be in sight.
Tosin Agbabiaka contracted polio in his home town, Lagos, when he was three years old. He discovered he had artistic talents and started to paint holding the brush in his mouth. "Polio makes life as if I am a beggar. Every Saturday I bring out my paintings for people to see and people start giving me money. I don't like that. I hate it," he said.
The oral polio vaccine could have prevented him from getting the disease.
Mass vaccinations against polio began in the 1950s. In developed nations, the disease was eradicated. But it still is problematic in some South Asian and African countries.
Scientists say, in two countries where polio is endemic, the new so-called double strain vaccine has been 30 percent more effective than the traditional triple strain vaccine. Human trials in Nigeria and India showed that most babies who got the new vaccine, made by two pharmaceutical companies, developed immunity to the two virulent strains of polio.
Dr. Peter Hotez is president of the Sabin Vaccine Institute in Washington DC.
He says the new vaccine provides stronger immunity. "The idea behind the new vaccine is to make it more immunogenic, that is better able to stimulate an immune response by concentrating just a number of strains that are in the new polio vaccine. So the traditional polio vaccine is sometimes called the trivalent vaccine. It has three
types type 1 - type 2 type 3. This one, the new one, has only two types with higher concentration of virus," he said.
Polio mostly affects children under the age of five and spreads rapidly in areas of poor sanitation. It attacks the nervous system, sometimes causing irreversible paralysis.
Dr. Hotez says eradicating polio has been more difficult than smallpox, for example. "If you are infected with smallpox you have dramatic symptoms. The problem with polio is that with for every one patient who develops paralytic polio there are 100 others who have no symptoms. So that way, it becomes a much more difficult disease to contain and it means that we have to vaccinate large segments of population to protect everybody," he said.
Local resistance to vaccines for political and cultural reasons has complicated the problem. The 2003 ban in Nigeria on polio vaccines caused a dramatic spike in infections not only in Nigeria. The virus spread to several neighboring countries including some where polio had been eradicated.
The World Health Organization says in the coming days about 70 million children in 15 countries across Africa will be vaccinated. Out of them, 55 million will get the new bivalent vaccine.
In some countries the virus has been more stubborn than others.
Dr. Peter Hotez said, "In the case of India, one of the thorny problems that's prevented complete success is the fact that some populations don't manifest as
robust immune response to the oral polio vaccine as say if we were giving it in the United States, and that may be because of underlying
malnutrition or underlying co-parasitic infection or diarrheal disease."
But according to the WHO, polio cases in India and Nigeria dropped by more than 90 percent after trials with the new vaccine. It says this could mean that eradicating polio is in sight.