A child receives oral polio vaccine during a 2002 campaign to forever 21 annual report 2015 pdf children in India. 37 confirmed cases in 2016.
Since 2011 incidence rates of the disease have dropped dramatically, and with large reductions continuing through to 2017, hopes for eliminating polio have been rekindled. Only three countries remain where the disease is endemic—Afghanistan, Pakistan and Nigeria. 2016 halved this figure to 37 cases. In theory, if the right tools were available, it would be possible to eradicate all infectious diseases that reside only in a human host. In reality there are distinct biological features of the organisms and technical factors of dealing with them that make their potential eradicability more or less likely.
Organization of “national immunization days” to provide supplementary doses of oral polio vaccine to all children less than five years of age. Active surveillance for wild poliovirus through reporting and laboratory testing of all cases of acute flaccid paralysis. Targeted “mop-up” campaigns once wild poliovirus transmission is limited to a specific focal area. Poliovirus is transmitted only through person-to-person contact and the transmission cycle of polio is from one infected person to another person susceptible to the disease, and so on.
When many hosts are vaccinated, especially simultaneously, the transmission of wild virus is blocked, and the virus is unable to find another susceptible individual to infect. Herd immunity is an important supplement to vaccination. Among those individuals who receive oral polio vaccine, only 95 percent will develop immunity. That means five of every 100 given the vaccine will not develop any immunity and will be susceptible to developing polio. According to the concepts of herd immunity this population whom the vaccine fails, are still protected by the immunity of those around them.
Herd immunity can only be achieved when vaccination levels are high. 86 percent of individuals in a population must be immune to polio for the susceptible individuals to be protected by herd immunity. If routine immunization were stopped, the number of unvaccinated, susceptible individuals would soon exceed the capability of herd immunity to protect them. Among the greatest obstacles to global polio eradication are the lack of basic health infrastructure, which limits vaccine distribution and delivery, the crippling effects of civil war and internal strife, and the sometimes oppositional stance that marginalized communities take against what is perceived as a potentially hostile intervention by outsiders. An independent evaluation of obstacles to polio eradication requested by the WHO and conducted in 2009 considered the major obstacles in detail by country. In Nigeria, meanwhile, the most critical barriers identified were management issues, in particular the highly variable importance ascribed to polio by different authorities at the local government level, although funding issues, community perceptions of vaccine safety, inadequate mobilisation of community groups, and issues with the cold chain also played a role. Angola and South Sudan for the purpose of curtailing the spread of polio and climatic factors were also identified as playing a role.
Two additional challenges are found in unobserved polio transmission and in vaccine-derived poliovirus. And since 2000, there have been a number of outbreaks of circulating vaccine-derived poliovirus, following mutations or recombinations in the attenuated strain used for the oral polio vaccine, which have raised the necessity of eventually switching to the more expensive inactivated polio vaccine. Gezari, WHO’s special envoy on global polio eradication and primary healthcare, gave his views on obstacles to eradication. He said the biggest hurdle in making Pakistan polio-free was holding district health officials properly accountable—in national eradication campaigns officials had hired their own relatives, even young children. How do you expect a seven-year-old thumb-sucking kid to implement a polio campaign of the government,” said Dr Gezari. He added that, in spite of this, “the first national campaign was initiated by your government in 1994 and that year Pakistan reported 25,000 polio cases, and the number was just 198 last year, which clearly shows that the programme is working.
One factor contributing to the continued circulation of polio immunization programs has been opposition in some countries. Pakistan that the United States was using immunization campaigns to sterilize the local population. CIA in using a vaccination campaign as a cover. Even with the express support of political leaders, polio workers have been kidnapped, beaten, and assassinated. Pakistan was suspended following the murder of nine vaccination workers. The killing of polio workers seen the previous year continued in 2013.