‘A Biological Side Effect’: Yaws Eradication, Syphilis, and Debates over ‘Cross-Immunity’ at the World Health Organization, 1948–1990

Abstract

Summary The World Health Organisation’s (WHO) yaws eradication campaign (1952–64) has been called ‘one of the greatest public health achievements’ of the twentieth century. Yet the campaign was not an unalloyed success. Shortly after its initiation, experts began to wonder if yaws’ disappearance might facilitate the spread of syphilis—whose genetic similarities with yaws had long fuelled speculation that the two treponemal diseases conferred a measure of immunological protection on each other. As the WHO’s work proceeded, evidence for this ‘cross-immunity’ hypothesis steadily accumulated from across the developing world. Though initially receptive to this idea, by the 1970s, WHO officials were increasingly downplaying the idea of cross-immunity, arguing instead that rising rates of syphilis were a product of the era’s ‘sexual revolution’. Animated by racialised discourses of sexual promiscuity, the WHO’s shifting treponemal discourse highlights important continuities between Cold War disease control efforts and the ‘colonial medicine’ of the early twentieth century.