BMC Public Health 2009, 9:310 http://www.biomedcentral.com/1471-2458/9/310 and/or that those included were measured with low valid- ity. The finding that neighbourhood and individual edu- cational attainment in the rural area tended to have contrasting associations with HIV prevalence (the first being protective and the second tending to be a risk fac- tor) supports the assumption that the aggregate variable for neighbourhood educational attainment captures not only differences in education itself but also important dif- ferences in the socio-economic context of the neighbour- hoods that may protect educated and wealthier neighbourhoods from HIV infection. To what extent education in itself creates the differences in HIV prevalence between neighbourhoods is difficult to judge. Although neighbourhood educational attainment seems to be a good proxy of structural neighbourhood dif- ferences in the present data, we cannot rule out the possi- bility that education per se plays a role too. For example, it is believed that the spread of education in the commu- nity environment moulds socially acceptable behaviour [24]. Young women in the most educated neighbour- hoods in this study seemed to delay sexual debut and mar- riage compared to those in the least educated neighbourhoods, and this may reflect differences in what is perceived to be socially acceptable. It could also reflect that women from educated neighbourhoods have a more independent position and are actively encouraged to pur- sue an education before establishing a relationship to a man and having children. Other studies suggest that in neighbourhoods with low average educational attainment or financially deprived areas adult supervision may be weaker [30]. As parental involvement may function as a social control and socialization mechanism in the family [30], limited parental involvement seems to be generally associated with a higher level of pre-marital sexual activity and problem behaviour [31]. This may be translated into higher chances of HIV infection among young women in the least educated neighbourhoods when compared with their peers who reside in areas with high average educa- tion. Further, educated women are more likely to marry educated men, and as educated men are less likely to engage in risky sexual behaviour [25] and they are less likely to be HIV infected, this probably also has an impact on the HIV risk of educated women. Past HIV prevention efforts have been overly focused on individual behaviours, but the recognition of the need to combine behavioural, structural and biomedical approaches seems to be growing [32,33]. Although the observed shift in the association between educational attainment and HIV prevalence in several high prevalence African countries might be an example of substantial effects of preventive programmes focused on individual behaviour [19,22,25,34], these preventive programmes seem to have had limited impact on the less educated and impoverished part of the population. There is still limited understanding of why the less educated are not adhering to behaviour change messages. The most educated may respond faster to protect themselves due to higher concern for their health and stronger belief in their own self-effi- cacy as predicted by the framework "diffusion of innova- tions" [25,35,36]. Or it might be rooted in the pedagogical approach employed by the campaigns. Any elements of 'blame the victim' approaches to foster behav- iour change messages may have been counter-productive or perceived as irrelevant by less educated persons [34]. The neighbourhood effects on HIV prevalence might indi- cate the need for combining programmes focussing on individual behaviour with structural approaches to address those factors that shape or constrain individual behaviour. An example of an important programme that may contribute to this is the Programme for the advance- ment of girls' education (PAGE), adopted in Zambia in the early 1990s, with the purpose to improve girls' access to school [37]. It seems that this programme has started to bear fruits in terms of substantial improvement in girls' school attendance at both primary and secondary level in the period 1990–2000 [38]. However, the net junior and senior secondary school attendance rate is still low in Zambia, particularly in rural (8% and 5% vs. 35% and 29% in urban areas) and low cost areas (31% and 23% vs. 50% and 49% in high cost areas)[39]. Increasing school attendance in low cost (poor) areas is likely to have an effect on HIV incidence as it may increase the self-efficacy of young people to protect themselves against HIV infec- tion and increase their chances of obtaining formal employment and thus improve their own living condi- tions. Making secondary schools more available in rural areas may be one way to increase net school attendance, and removing school fees is another. A number of factors may have contributed to biasing the neighbourhood effects in our study. In the first place, cen- sus clusters may not be adequate proxies of an individual's neighbourhood surroundings and thus may not ade- quately capture differences across neighbourhoods [8]. However, these areas are small enough to be useful prox- ies of the natural neighbourhoods. Furthermore, the number of clusters used by the study was low; i.e. 10 in each of the strata. This resulted in low power to detect in- between cluster variation in HIV prevalence[40]. There was also limited information on more specific neighbour- hood characteristics found to be related to HIV prevalence in other studies, for example, availability of water, mar- kets and health facilities [13] and availability of bars and proximity to the nearest big town [14]. Non-response may have affected our results if young women who were absent during the household visits had a different risk profile than those found at home (e.g. young women attending boarding school could engage in both less or more risky Page 9 of 11 (page number not for citation purposes)