Free WinPing 2.5512/22/2023 ![]() ![]() Vaccines against each of the three wild strains of polio have given rise to strains of cVDPV, with cVDPV2 being most prominent. ![]() ![]() Recent polio cases arise from two sources, the original ' wild' poliovirus (WPV), and the much more prevalent mutated oral vaccine strains, known as circulating vaccine-derived poliovirus (cVDPV). Wild poliovirus has been eradicated in all continents except Asia, and as of 2020, Afghanistan and Pakistan are the only two countries where the disease is still classified as endemic. Nigeria is the latest country to have officially stopped endemic transmission of wild poliovirus, with its last reported case in 2016. IPV is more costly and the logistics of delivery are more challenging. Being inactivated, IPV is free of these risks but does not induce contact immunity. However, under conditions of long-term vaccine virus circulation in under-vaccinated populations, mutations can reactivate the virus to produce a polio-inducing strain, while OPV can also, in rare circumstances, induce polio or persistent asymptomatic infection in vaccinated individuals, particularly those who are immunodeficient. It has been the predominant vaccine used. OPV is less expensive and easier to administer, and can spread immunity beyond the person vaccinated, creating contact immunity. ![]() There are two kinds of polio vaccine-oral polio vaccine (OPV), which uses weakened poliovirus, and inactivated polio vaccine (IPV), which is injected. Prevention of disease spread is accomplished by vaccination. Successful eradication of infectious diseases has been achieved twice before, with smallpox in humans and rinderpest in ruminants. Centers for Disease Control and Prevention (CDC) and The Gates Foundation, have spearheaded the campaign through the Global Polio Eradication Initiative (GPEI). Polio eradication, the permanent global cessation of circulation of the poliovirus and hence elimination of the poliomyelitis (polio) it causes, is the aim of a multinational public health effort begun in 1988, led by the World Health Organization (WHO), the United Nations Children's Fund (UNICEF) and the Rotary Foundation. A child receives oral polio vaccine during a 2002 campaign to immunize children in India. ![]()
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