Polio will soon be history
The Bulletin interview with David Heymann and Bruce Aylward.
When the Global Polio Eradication Initiative was launched in 1988, there were more than 350 000 cases a year in more than 125 countries. In 2003, there were just 784 cases. This year will be critical for the initiative led by WHO, Rotary International, US Centers for Disease Control and Prevention and UNICEF. If vaccination campaigns can immunize all children in Afghanistan, India, Nigeria and Pakistan, where the disease remains endemic, polio will be history within a few years.
Dr David Heymann earned his MD at Wake Forest University in his native United States. His public health career has spanned more than 30 years as he worked on smallpox eradication in India in the 1970s and began many years of service for the US Centers for Disease Control and Prevention. He participated in the first investigation of Ebola fever in Africa in 1976, and in 1995 led the international response to outbreaks of the disease. As executive director of the WHO Programme on Emerging and Other Communicable Diseases cluster of departments from 1998 until 2003, he led WHO’s efforts to fight severe acute respiratory syndrome (SARS). In 2003, he was appointed representative to the director-general for polio eradication. In 2006, he became acting assistant director-general for WHO’s Communicable Diseases cluster of departments and the director-general’s representative for pandemic influenza.
Q: The world is 99% of the way towards eradicating polio; when will we finish the job?
A: We have a new vaccine in use, a monovalent oral polio vaccine (OPV) which gives better protection for fewer doses of vaccine, and we have very high levels of commitment in all the countries that still have polio. If in the remaining four endemic countries all children can be immunized during polio campaigns, polio will be eradicated within the next two years.
Q: India has made great progress, so it was shocking to see a new outbreak of more than 500 cases in 2006 compared with 66 in 2005.
A: The resurgence of cases in India, while disappointing, was not completely unexpected, because every four years there is an epidemic and the last one was in 2002. However, this epidemic is significantly smaller than the one four years ago, due to the use of monovalent OPV since May 2005. At that time, polio was present in the states of Bihar and Uttar Pradesh, and in Maharashtra state in Mumbai. The monovalent vaccine took out polio in Mumbai, and in Bihar strong progress continues. But in Uttar Pradesh, vaccination coverage started to decrease right when the monovalent vaccine was introduced. While coverage increased again this year, the decrease led to a build-up of susceptible children and now we’re seeing the increase in cases.
Q: Isn’t it possible to do a quick fix there?
A: There is never a single quick fix, but rather a range of activities that we are continuing to do in support of the government of India. For example, many state government medical officers’ positions in Uttar Pradesh, are vacant so many of WHO’s medical officers have been shifted there from other states to make sure eradication activities are being conducted.
Q: How can WHO see to it that the structures developed for the polio initiative are used to fight other diseases?
A: The infrastructure consists of over 3000 workers at country level. Those workers are detecting suspected polio cases, collecting specimens and sending them to the laboratory network where polio is identified. It is a very valuable network and has been used for other disease outbreaks many times at country level, for example in Angola in 2005 when the outbreak of Marburg fever occurred.
Q: Why was it easier to eradicate smallpox than polio?
A: Smallpox eradication was a much easier programme because every infection was clinically expressed in the same manner, so you could tell easily when someone had the disease. Also, once you found that a person had smallpox you could isolate them and vaccinate a ring of people around that person. With polio, for every clinically expressed paralysis there are at least 200 children infected asymptomatically, which means you can’t find every polio infection.
Q: What are the risks after polio has been declared eradicated?
A: Once polio has been eradicated, the risk of polio associated with oral polio vaccine will be greater than the risk of naturally occurring polio because oral polio vaccine can cause — in very rare instances — vaccine-associated paralytic poliomyelitis. At the same time the oral polio vaccine virus has the potential to mutate and actually cause outbreaks. Though this is also extremely rare, use of oral polio vaccine from routine immunization programmes will have to be stopped and countries will have to do it through a mechanism on which we are beginning now to agree.
Q: Could polio virus be used as a bio-weapon after it has been eradicated?
A: Any organism can be used as a bio-weapon. It just depends on what a bioterrorist is trying to accomplish. If a polio virus is introduced somewhere and children become paralysed, there will be great concern. Having said that, due to its characteristics, the polio virus would probably not make a particularly effective bio-weapon.