Stop Transmission of Polio (STOP). A mother holding her child while displaying a polio vaccination record, which indicates the child has been properly vaccinated. She and her child were visited by the health care practitioner at right, who was making the rounds from house to house to conduct interviews and find out which children had, or had not been, properly vaccinated. There are two kinds of polio vaccine: IPV, which is a shot given in the leg or arm, depending on age, which is recommended in the United States today, and a live, oral polio vaccine, or OPV, (drops that are swallowed). In the case of children, IPV may be given at the same time as other vaccines. Most people should receive a polio vaccine when they are children. Until recently OPV was recommended for most children in the United States. Both vaccines give immunity to polio, but OPV is better at keeping the disease from spreading to other people. However, for a few people (about one in 2.4 million), OPV actually causes polio. Since the risk of getting polio in the United States is now extremely low, experts believe that using oral polio vaccine is no longer worth the slight risk, except in limited circumstances. The polio shot (IPV) does not cause polio.The poliovirus, an enterovirus, enters through the mouth, and primary multiplication of the virus occurs at the site of implantation in the pharynx and gastrointestinal tract. The virus is usually present in the throat and in the stool before the onset of illness. One week after onset there is little virus in the throat, but virus continues to be excreted in the stool for several weeks. The virus invades local lymphoid tissue, enters the blood stream, and then may infect cells of the central nervous system. Replication of poliovirus in motor neurons of the anterior horn and brain stem results in cell destruction and causes the typical manifestations of poliomyelitis. Uttar Pradesh in northern India.