Polio vaccine 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. 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
Jonas Salk austere", wrote "The New York Times", "Salk the man is a person of great warmth and tremendous enthusiasm. People who meet him generally like him." A Washington newspaper correspondent commented, "He could sell me the Brooklyn Bridge, and I never bought anything before." Award-winning geneticist Walter Nelson-Rees called him "a renaissance scientist: brilliant, sophisticated, driven ... a fantastic creature." He enjoys talking to people he likes, and "he likes a lot of people", wrote the "Times". "He talks quickly, articulately, and often in complete paragraphs." And "He has very little perceptible interest in the things that interest most people—such as