During the polio epidemics of the 1940s and 1950s, even while Salk was preparing the injectable killed virus vaccine, the goal of eradication of polio from the earth wasn't something that anyone considered possible. Getting the injectable killed virus vaccine along with the Sabin live vaccine to children in the USA, Britain, and other developed countries was the goal. And soon it proved to be a successful undertaking as virtually all schoolchildren and others were vaccinated. Now for several years we have not had a single case of polio in the developed world.
When Sabin introduced his live mutated avirulent (unable to cause polio) virus vaccine some began to think that eradication of polio could be achieved if vaccine could be made available throughout the world. The reason that the Sabin vaccine was a game changer was because of the properties of this live weakened virus. It spread throughout a population so that even unvaccinated individuals could be infected conferring immunity in them. There is a small chance that the vaccine can mutate back to a virulent strain so oral polio vaccine will eventually be withdrawn and the injectable dead vaccine can mop up the very few remaining cases in the world.
The live Sabin vaccine confers "Herd Immunity" to a population. Thus, eradication of polio from the entire world only depended on getting the Sabin vaccine to the populations of only a handful of countries. The Sabin vaccine is only 95% successful so for every 100 children vaccinated 5 will still go unprotected. Nevertheless, coverage of 95% will lower the virus load within the population to protect all. This is Herd Immunity. In order to contract polio three situations must be present:
1. Live polio virus
2. A method of transmission (contact between individuals)
3. Susceptible hosts (people)
So Herd Immunity should remove enough susceptible hosts to stop polio in it's tracks.
With anticipated success as with smallpox before it, polio would become a vaccine rather than a disease. The effort to exterminate polio was started in 1988, when there were hundreds of thousands of cases, now only 291 cases were reported in 2012. It seemed with this success that it would be a cakewalk to eliminate such small numbers but there have been setbacks and frustrations to get the last holdout countries safely vaccinated.
Getting some third world countries vaccinated turned out to be a difficult task for reasons discussed below. Now in 2013 we are so close to the goal that we know we will achieve it despite the barriers to that effort. The Global Polio Eradication Initiative consists of the World Health Organization, the United Nations Children's Fund (UNICEF), Rotary International, the Bill and Melinda Gates Foundation, and the Communicable Disease Center in Atlanta. These partners, working toward the eradication, have been frustrated because, as of this date, we have an outbreak in Somalia, and endemic infection in Nigeria, Afghanistan, and Pakistan. We have solved the logistical problem of keeping the vaccine refrigerated even in warm inaccessible African countries but there are political barriers to the continuing effort.
Recently in Pakistan vaccine volunteers, providing vaccine, were killed by a group of armed men. This brings to ten the polio volunteers killed in Pakistan. The Taliban have issued threats asserting that vaccine workers were spies or that they were trying to make Pakistanis sterile. The CIA in the hunt for Bin Laden used an alias of a doctor vaccinating children so now true efforts like the polio vaccine program are under Taliban attack. Even people who want to bring the vaccine to their children are afraid of being caught and killed..These incidents have suspended the UNICEF workers from vaccinating children in the north-west and in southern Pakistan. It remains uncertain when these efforts will resume. It is also dangerous to get inside Somalia where chaos rules through warlords and terrorists. Somalia has the latest outbreak of polio paralyzing more than a hundred children. In Israel there haven't been any new cases but virulent poliovirus has been recovered from sewage pointing to the potential for new infection. See more on this below.
Despite these setbacks there is a global plan for ridding the world of polio by 2018. The plan contains four objectives:
Some current facts about where efforts should be concentrated are:
- Poliovirus detection and interruption
- Immune systems strengthened and oral polio vaccine withdrawn..This objective includes withdrawal of the oral polio vaccine because some new cases have been contracted from polio virus derived from weakened Sabin vaccine which had back mutated to the virulent strain.
- Containment and Certification: This includes safe handling of virus samples at various labs around the world along with the production of polio vaccine to quickly eliminate any new infections and also as a source of new vaccine.
- Legacy planning: This includes Governance, risk assessment, mitigation of any new polio, monitoring, oversight and contingency planning. There is more in depth information about these objectives at: www.polioeradication.org/Resourcelibrary/Strategyandwork.aspx
- In Ethiopia an 18 month old infant was infected with wild polio virus. The baby came from the Somali region.
- In Israel this year in 68 samples from sewage were positive for wild polio virus though there were no infections.
- In Somalia more than 100 cases in children occurred in 2013 as mentioned above.
- In the interior of Nigeria there are unvaccinated native peoples which will need to be vaccinated.
- In Pakistan there are endemic new cases of polio. There is concern for a larger outbreak among unvaccinated populations in areas controlled by extremists.
"The Somali outbreak is now forcing UNICEF, the WHO and other international agencies to dedicate vast resources to boost polio vaccination coverage throughout East Africa and parts of the Middle East. Those are resources that can't be used to attack the virus in Afghanistan, Pakistan and Nigeria - which appeared, until now, to be the last few places where polio had a foothold." - See more at: and at: www.polioeradication.org/tabid/488/iid/318/Default.aspx. The latter provides up to date information regarding the strategic elimination of polio by 2018. Also the following pages can be used for a resource on all efforts to eliminate polio from the world.
Hope has been rekindled through successful elimination of polio from India which will reinforce vaccine workers to bring available resources to the remaining hotspots. Despite the problems discussed above the organizations involved in this effort are insistent that the eradication date of 2018 will be met. Then we will have to decide whether we will keep the virus in the lab for further study or if even lab samples will be destroyed to result in extinction of the virus.
© Professor Edward P. Bollenbach
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