What is Polio vaccine?
[[File:Poliodrops.jpg|thumb|150x150px|child is vaccinated against Polio]] '''Polio vaccines''' are [[vaccines]] that prevent [[poliomyelitis]] (or polio). Two types of polio vaccines are used throughout the world. The first type was developed by [[Jonas Salk]] and first tested in 1952. Announced to the world by Salk on April 12, 1955, it is an injection of inactivated (dead) [[poliovirus]]. The second type was an oral vaccine developed by [[Albert Sabin]], using [[Attenuated virus|attenuated]] poliovirus. An attenuated virus is a much less harmful strain of the same virus. [[Clinical trial|Human trials]] of Sabin's vaccine began in 1957 and it was licensed in 1962.<ref>{{cite web | title = A Science Odyssey: People and Discoveries | publisher = PBS | year = 1998 | url = https://www.pbs.org/wgbh/aso/databank/entries/dm52sa.html | accessdate = 2008-11-29}}</ref> There is no long term carrier for poliovirus (carriers are people who carry the virus but have no symptoms of the disease), and polioviruses have no non-primate reservoir in nature. The virus cannot survive in the open environment for a long time. Therefore, interruption of person to person transmission of the virus by vaccination is the key step in removing polio entirely.<ref name=Fine>{{cite journal |author=Fine P, Carneiro I |title=Transmissibility and persistence of oral polio vaccine viruses: implications for the global poliomyelitis eradication initiative |url= http://aje.oxfordjournals.org/cgi/reprint/150/10/1001| journal=Am J Epidemiol |volume=150 |issue=10 |pages=1001–21 |date=15 November 1999|doi=10.1093/oxfordjournals.aje.a009924 |pmid=10568615 }}</ref> The two vaccines have eliminated polio from most countries in the world.<ref name=Aylward_2006>{{cite journal |author=Aylward RB |title=Eradicating polio: today's challenges and tomorrow's legacy |journal=Annals of Tropical Medicine and Parasitology |volume=100 |issue=5–6 |pages=401–13 |year=2006 |pmid=16899145 |doi=10.1179/136485906X97354 |s2cid=25327986 |url=http://openurl.ingenta.com/conte