In 2001, a school teacher in Gueckedou, on Guinea’s border with Liberia, saw rebel forces including child soldiers destroy his town. Reflecting a few years later on the childhood immunization programmes that are now well established in the region, he worried that they might be creating a new generation of children – strengthened, but more violent. The notion of strength, and the processes that build or deplete it, is central to local understanding of many issues in this part of west Africa – from health to the power of communities and regions. Not surprisingly, people have come to frame and evaluate immunization and its effects through this particular logic. Much of the time, they do so appreciatively. Yet, as this teacher expressed, the strengthening effects of immunization can also be a source of ambivalence and anxiety. Awareness of local social and cultural perspectives such as these can greatly assist in meeting the challenges associated with immunization programmes. Since the 1950s, immunization has brought nine major diseases under varying degrees of control and has achieved remarkable success as a universal technology promoted through globalized approaches. Yet, as immunization plays into diverse personal, social and cultural worlds, its reception has varied: there is acceptance and increasingly active demand among many, but anxiety, distrust, refusal and resistance among others. Today, scientific and technological advancements, coupled with growing international and philanthropic investment, are making strides in addressing the “supply-side” challenges of immunization. Addressing the “demand side” challenges assumes relatively greater importance for expanding immunization coverage. Health professionals often assume that low demand or refusal reflects public ignorance or misinformation that needs to be corrected through education. Recent cases of resistance to immunization – such as to tetanus toxoid campaigns in Cameroon and Uganda and oral polio vaccines in Nigeria – have reignited concern over “anti-vaccination rumours”. Yet assumptions of ignorance and rumour overlook the effect of local knowledge and cultural perspectives on leading people to demand or shun immunization. In the Gambia, for example, mothers value immunization as introducing a powerful substance into the blood, building its defences against disease: “The injection strengthens the health of the child. It gives the child good body.” Within this logic, many believe that vaccinations are effective against illness in general. In a survey, 29% of urban and 48% of rural mothers could not correctly name any biomedically vaccinable diseases, yet were actively seeking immunization – reflected in national coverage rates of 90% in 2003. Such ideas about strength, fluid and substance do not conform to biomedical notions yet they are the foundation behind a strong appreciation of immunization in areas across the Gambia, Guinea, Sierra Leone and beyond.1 The same belief can also underlie anxiety. Mothers who regularly miss clinic sessions often worry that a backlog of vaccinations will have “stacked up” and that nurses will give their child several at once. They believe that this can be too much substance for the blood and body to cope with. In these west African regions, ideas of strength and proper circulatory flow frame not just bodily, but also wider social and political reflection. Routine immunization delivery by trusted health agents is interpreted as part of the valued throughflow of people and goods that builds healthy, strong communities. Vaccination has long been delivered primarily by the government, promoting the notion that strong bodies help to build a populous, strong national body politic. Yet within this context, vaccination services can also be perceived as weakening the community. Rumours that vaccines contain sterilizing agents or HIV can make sense in these terms, which link individual weakening with weakening of the body politic, as a population or area is sapped of fertility and strength. In contrast with routine health delivery, externally-led, one-off vaccination campaigns and National Immunization Days do not become part of local strength-building relations. Instead, it is easy for campaigns to be experienced as invasive and alien, and this calls into question their agenda. These perspectives provide a further layer to White’s2 argument that international disease eradication programmes in Africa have – since the 1960s – often been experienced as a kind of “un-national sovereignty”. To understand why people accept (and why they sometimes reject) immunization requires engagement with local cultural perceptions of both the technologies involved and of the approach of particular programmes. Appreciating them is essential when developing strategies to improve immunization uptake, to design effective and acceptable programmes, and to build appropriate, dialogue-based communication approaches. ■