In the mid-20th century, poliovirus paralysed half a million children a year, in rich countries as well as poor. In 1952 there were 57,628 cases in the United States. Following the development of vaccines by Jonas Salk and Albert Sabin, polio declined markedly in North America and Europe. The US had its last case in 1979, the UK in 1982. There were still, however, about 350,000 cases a year in the mid-1980s, predominantly in countries where the state did not have the money or capacity to implement mass vaccination programmes. The Global Polio Eradication Initiative was formed in 1988 by the WHO and national governments to finance and organise immunisation campaigns. It precipitated a sharp reduction in polio: there were 37 cases in the world in 2016, a fall of 99.9 per cent. But the disease stubbornly persists in Nigeria, Afghanistan and Pakistan.