Comment For more on the Commission on Social Determinants of Health see http://www.who.int/social_ determinants/thecommission/en/ health care are to be universal human rights, then we need to understand how unfair the distribution is of both health status and health services Second, examination of the equitable distribution of key indicators of social determinants of health I propose four: early child development at age years; the proportion of young people not in employment, education, or training; an adult poverty measure; and a measure of social isolation or poverty or both in people older than working age Problems of international comparability will arise, but these are soluble, as shown by the Human Development Reports or regular World Bank reports Personally, I would not stop there I would want the monitoring framework to include inequities in power, money, and resources—the structural drivers of health inequity highlighted by the Commission on Social Determinants of Health For example, in London, UK the effects of the economic downturn on health equity will be monitored by indicators of employment, economic security, housing, and migration Although these are all important, the four areas I have proposed are eminently doable, and should be done, by any country that is serious not just about ensuring universal coverage of health services but equity in health of its population Michael Marmot UCL Institute of Health Equity and Department of Epidemiology and Public Health, University College London, London WC1E 7HB, UK m.marmot@ucl.ac.uk I declare that I have no conflicts of interest WHO Declaration of Alma-Ata International conference on primary health care; Almaty, Kazakhstan, formerly Alma-Ata, USSR; Sept 6–12, 1978 Commission on the social determinants of health Closing the gap in a generation: health equity through action on the social determinants of health Final report of the commission on social determinants of health Geneva: World Health Organization, 2008 WHO Universal health coverage: what is universal health coverage? http:// www.who.int/universal_health_coverage/en/index.html (accessed Sept 4, 2013) WHO What is universal health coverage? Oct, 2012 http://www.who.int/ features/qa/universal_health_coverage/en/index.html (accessed Sept 9, 2013) United Nations General Assembly Global health and foreign policy Dec 6, 2012 http://www.un.org/ga/search/view_doc.asp?symbol=A/67/ L.36&referer=http://www.un.org/en/ga/info/draft/index.shtml&Lang=E (accessed Sept 9, 2013) WHO WHO/World Bank convene ministerial meeting to discuss best practices for moving forward on universal health coverage 2013 Feb 19, 2013 http://www.who.int/mediacentre/news/statements/2013/ uhc_20130219/en/index.html (accessed Sept 4, 2013) Stuckler D, Basu S The body economic: why austerity kills New York: Basic Books, 2013 Bloomer E, Allen J, Donkin A, Findlay G, Gamsu M The impact of the economic downturn and policy changes on health inequalities in London Aug 13, 2013 https://www.instituteofhealthequity.org/projects/ demographics-finance-and-policy-london-2011-15-effects-on-housingemployment-and-income-and-strategies-to-reduce-health-inequalities (accessed Sept 4, 2013) Allen M, Allen J, Hogarth S, Marmot M Working for health equity: the role of health professionals March, 2013 http://www.instituteofhealthequity org/projects/working-for-health-equity-the-role-of-health-professionals (accessed Sept 4, 2013) A probiotic trial: tipping the balance of evidence? Published Online August 8, 2013 http://dx.doi.org/10.1016/ S0140-6736(13)61571-8 See Articles page 1249 Copyright © Daneman Open Access article distributed under the terms of CC BY-NC-ND 1228 Clostridium difficile is the most burdensome gastrointestinal infection and one of the main infectious causes of morbidity and mortality in industrialised countries.1 Prevention of C difficile infection relies on methods to reduce transmission of the pathogen, through effective hand hygiene, barrier precautions, isolation of patients, and environmental cleaning Perhaps even more important are attempts to reduce host susceptibility to infection by decreasing unnecessary antibiotic use.2 Antibiotic use disrupts and depletes the normal gastrointestinal flora, allowing C difficile to thrive and generate clinical disease.3 When antibiotic treatment is unavoidable, reinforcement of the colonic flora might be another means to decrease susceptibility of patients to C difficile Definitive restoration of the colonic ecosystem through stool transfer has unequivocal benefit in treatment of established C difficile infections and prevention of recurrences.4 A more palatable, or at least less pungent, approach to boost colonic defences is the use of non-pathogenic microbial supplements—known as probiotics Probiotics have been widely marketed in commercial preparations, and widely studied as a means to prevent C difficile Two recent meta-analyses have summarised the results of previous trials, detecting large reductions in the risk of antibiotic-associated diarrhoea (AAD) in general (relative risk [RR] 0·58, 95% CI 0·50–0·68)5 and C difficile infections in particular (0·34, 0·24–0·49).6 These impressive effect sizes are motivating many health-care institutions to consider routine probiotic coadministration with antibiotic treatments However, in The Lancet, Stephen Allen and colleagues7 question the usefulness of routine probiotics Their PLACIDE trial, done at five centres in England and Wales, is the largest trial to be reported in this discipline (n=2941) The study is rigorous, with central www.thelancet.com Vol 382 October 12, 2013 Comment Experimental Control Events Total Events Risk ratio (95% CI) Weight Total 0·71 (0·34–1·47) 19·0% 12 1470 17 1471 Arvola et al, 1999 61 58 0·95 (0·06–14·85) 1·4% Beausoleil et al, 2007 44 45 0·15 (0·02–1·14) 2·4% Bravo et al, 2008 41 45 NE Can et al, 2006 73 78 0·21 (0·01–4·37) Duman et al, 2005 196 180 0·31 (0·01–7·47) 1·0% Gao et al, 2010 171 20 84 0·22 (0·11–0·46) 18·7% Hickson et al, 2007 56 53 0·05 (0·00–0·84) 1·3% Kotowska et al, 2005 119 10 127 0·32 (0·09–1·14) 6·4% Lonnermark et al, 2005 80 83 3·11 (0·13–75·26) 1·0% McFarland et al, 1995 97 96 0·74 (0·17–3·23) 4·8% Miller et al, 2008 95 94 0·57 (0·17–1·87) 7·2% Miller et al, 2008 157 159 Plummer et al, 2004 69 Psaradellis et al, 2010 216 Rafiq et al, 2007 45 Ruszczynski et al, 2008 120 Safdar et al, 2008 23 Selinger et al, 2011 Surawicz et al, 1989 Thomas et al, 2001 52 Allen et al, 2013 Total 1·1% 5·06 (0·25–104·63) 1·1% 69 0·40 (0·08–1·99) 4·0% 221 0·26 (0·03–2·27) 2·2% 22 55 0·28 (0·11–0·67) 13·1% 120 0·43 (0·11–1·62) 5·8% 17 0·25 (0·01–5·79) 1·0% 62 62 NE 116 64 0·33 (0·08–1·34) 133 134 0·67 (0·11–3·96) 3444 125 3315 0·39 (0·29–0·54) Heterogeneity: τ2=0·00; χ2=15·08, df=18 (p=0·66); I2=0% Test for overall effect: Z=5·69 (p