Poliomyelitis, often called polio or infantile paralysis, is an acute viral infectious disease spread from person to person, primarily via the fecal-oral route. The term derives from the Greek poliós, meaning "grey", myelós, referring to the "spinal cord", and the suffix -itis, which denotes inflammation. It is an infection that exhibits no symptoms in 95 percent of the cases. One to two percent develops stiffness in the neck, back, and legs, while less than one percent experience paralysis. For the rest, polio manifests itself through sore throat, vomiting, and low-grade fever.
To prevent the reentry of the disease two vaccines are used throughout the world to combat polio. Both vaccines induce immunity to polio, efficiently blocking person-to-person transmission of wild poliovirus, thereby protecting both individual vaccine recipients and the wider community (so-called herd immunity). The first inactivated virus vaccine was developed in 1952 by Jonas Salk, and announced to the world on April 12, 1955. The Salk vaccine, or inactivated poliovirus vaccine (IPV), is based on poliovirus grown in a type of monkey kidney tissue culture (Vero cell line), which is chemically inactivated with formalin.Subsequently, Albert Sabin developed an oral polio vaccine (OPV) using live but weakened (attenuated) virus, produced by the repeated passage of the virus through non-human cells at sub-physiological temperatures. Human trials of Sabin's vaccine began in 1957 and it was licensed in 1962. The attenuated poliovirus in the Sabin vaccine replicates very efficiently in the gut, the primary site of wild poliovirus infection and replication, but the vaccine strain is unable to replicate efficiently within nervous system tissue.
Because OPV is inexpensive, easy to administer, and produces excellent immunity in the intestine (which helps prevent infection with wild virus in areas where it is endemic), it has been the vaccine of choice for controlling poliomyelitis in many countries. On very rare occasions (about 1 case per 750,000 vaccine recipients) the attenuated virus in OPV reverts into a form that can paralyze. Most industrialized countries have switched to IPV, which cannot revert, either as the sole vaccine against poliomyelitis or in combination with oral polio vaccine.
To prevent the reentry of the disease two vaccines are used throughout the world to combat polio. Both vaccines induce immunity to polio, efficiently blocking person-to-person transmission of wild poliovirus, thereby protecting both individual vaccine recipients and the wider community (so-called herd immunity). The first inactivated virus vaccine was developed in 1952 by Jonas Salk, and announced to the world on April 12, 1955. The Salk vaccine, or inactivated poliovirus vaccine (IPV), is based on poliovirus grown in a type of monkey kidney tissue culture (Vero cell line), which is chemically inactivated with formalin.Subsequently, Albert Sabin developed an oral polio vaccine (OPV) using live but weakened (attenuated) virus, produced by the repeated passage of the virus through non-human cells at sub-physiological temperatures. Human trials of Sabin's vaccine began in 1957 and it was licensed in 1962. The attenuated poliovirus in the Sabin vaccine replicates very efficiently in the gut, the primary site of wild poliovirus infection and replication, but the vaccine strain is unable to replicate efficiently within nervous system tissue.
Because OPV is inexpensive, easy to administer, and produces excellent immunity in the intestine (which helps prevent infection with wild virus in areas where it is endemic), it has been the vaccine of choice for controlling poliomyelitis in many countries. On very rare occasions (about 1 case per 750,000 vaccine recipients) the attenuated virus in OPV reverts into a form that can paralyze. Most industrialized countries have switched to IPV, which cannot revert, either as the sole vaccine against poliomyelitis or in combination with oral polio vaccine.
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