The results of these human trials have been controversial, and unfounded accusations in the 1990s arose that the vaccine had created the conditions necessary for transmission of simian immunodeficiency virus from chimpanzees to humans, causing HIV/AIDS. These hypotheses, however, have been conclusively refuted. By 2004, cases of poliomyelitis in Africa had been reduced to just a small number of isolated regions in the western portion of the continent, with sporadic cases elsewhere. Recent local opposition to vaccination campaigns have evolved due to lack of adequate information, often relating to fears that the vaccine might induce sterility. The disease has since resurged in Nigeria and in several other African nations without necessary information, which epidemiologists believe is due to refusals by certain local populations to allow their children to receive the polio vaccine. Manufacture
Inactivated
The Salk vaccine, IPV, is based on three wild, virulent reference strains, Mahoney (type 1 poliovirus), MEF-1 (type 2 poliovirus), and Saukett (type 3 poliovirus), grown in a type of monkey kidney tissue culture (Vero cell line), which are then inactivated with formalin. The injected Salk vaccine confers IgG-mediated immunity in the bloodstream, which prevents polio infection from progressing to viremia and protects the motor neurons, thus eliminating the risk of bulbar polio and post-polio syndrome. In the United States, vaccine is administered along with the tetanus, diphtheria, and acellular pertussis vaccines (DTaP) and a pediatric dose of hepatitis B vaccine. In the UK, IPV is combined with tetanus, diphtheria, pertussis, and Haemophilus influenzae type b vaccines.
Poliovirus Vaccines at the US National Library of Medicine Medical Subject Headings (MeSH)