Introduction Epidemiological studies inform understanding of influences on health. Findings can lead directly to policy changes, but such changes need assessing, using formal intervention studies. Methods The Southampton Women's Survey is a longitudinal birth cohort with data collected on the mothers before conception. 12 583 women aged 20e34 years were assessed when not pregnant; 3159 were then followed through pregnancy and the children are followed-up. Results Maternal vitamin D levels in

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... gnancy were positively associated with markers of bone development in the children. Women's educational attainment was strongly related to the quality of their diets before conception, which in turn predicted the quality of the diets of their infants and children. Variations in infant diet were related to body composition at the age of 4 years. Our findings have led to intervention studies. Firstly, we are conducting a randomised controlled trial of vitamin D supplementation in pregnancy (MAVIDOS). Secondly, in relation to our diet quality findings, we are conducting a complex intervention, in collaboration with local policy makers, in which staff working in centres for women and children in disadvantaged areas are trained to engage in 'healthy conversations' with young women visiting the centres, to enable them to improve their diets and lifestyles (Southampton Initiative for Health). A school intervention (LifeLab) is also being developed. Conclusion The Southampton Women's Survey, a large epidemiological study, has led to the development of interventions to improve health of women and their children. These are being evaluated to inform policy, locally, nationally, and internationally. Introduction Droplet spread and direct contact are crucial factors in influenza transmission. Mass gatherings (MG) seem to provide ideal conditions for transmission. This systematic review examined the evidence for an association between MG and influenza transmission, and assessed whether restricting MG is effective at reducing or preventing transmission. Methods The published literature to July 2010 was reviewed by searching major databases (Pubmed, EMBASE, Scopus, and CINAHL), producing a combined list of 1670 articles that was sifted for relevance by title, abstract, and full-text assessment. A narrative approach was adopted for data synthesis. Results 18 papers met the inclusion criteria, covering MG of varying sizes and settings, and including 5 observational studies, nine outbreak reports, three event surveillance reports, and a quasiexperimental study. There is evidence that some MG are associated with increased risk of influenza transmission. MG can also be "seeding" events for introducing new strains to an area, and may instigate community transmission in the early stages of a pandemic. Restriction of MG, in combination with other social distancing interventions, may help reduce transmission, but evidence is lacking on the effect of MG restriction alone. Conclusion The evidence suggests that crowd density and event duration may be the key characteristics of an MG that determine the risk of influenza transmission. The type of venue (indoor or outdoor) also seems crucial. These considerations could potentially underlie the development of evidence-based, risk-dependent, policy-making frameworks for restricting MG in pandemic situations. Voluntary rather than legislated restrictions may be suitable.