Oral Rehydration Solution
This is an interim intervention report. We have published a more recent version of this page, where we consider the benefits alongside therapeutic zinc supplementation. See our most recent report on this program.
- What is the program? Oral rehydration solution (ORS) is a type of fluid replacement used to prevent and treat dehydration due to diarrhea.
- What is its evidence of effectiveness? Our impression is that it is widely accepted that ORS is effective at reducing mortality due to diarrhea. There is strong evidence that ORS is roughly as effective as intravenous fluids at rehydrating children in hospital settings, so we would guess that ORS is highly effective at reducing mortality in hospitals. There are no randomized studies of ORS in community settings, potentially because it would not be possible to get ethical approval for such a trial. Due to the lack of randomized trials, we are uncertain of the likely magnitude of mortality risk reduction in community ORS programs.
- How cost-effective is it? We estimate that this program is below the range of cost-effectiveness of programs we would direct funding to, but we have enough uncertainty and it is close enough to our threshold that we think additional work is reasonably likely to change our mind.
- Does it have room for more funding? We have not yet completed a full room for more funding analysis of ORS programs. We believe there may be substantial room for more funding based on conversations with charities implementing ORS programs.
- Bottom line: This program appears potentially promising, and we may revisit this intervention in the future.
Published: September 2017; Last updated: March 2021 (2017 version)
We revisited the evidence for this intervention in July 2020 and concluded that this report is up to date. We updated the cost-effectiveness sections of this report in March 2021.
Published: September 2017; Last updated: March 2021 (2017 version)
Table of Contents
What is the problem?
Diarrheal disease is the frequent passing of loose or liquid stools,1 usually caused by an infection of the intestinal tract.2 Infections are most commonly transmitted through faeces-contaminated water or food.3 Diarrhea generally causes death via severe dehydration and fluid loss, but septic bacterial infections and other causes account for an increasing proportion of deaths.4 Diarrhea is a significant cause of morbidity and mortality in low- and middle-income countries. The World Health Organization (WHO) estimated in 2017 that diarrhea kills about 525,000 children under five years old each year.5 We have not vetted this estimate.
What is the program?
Oral rehydration solution (ORS) is a type of fluid replacement used to prevent and treat dehydration due to diarrhea. ORS programs typically deliver a packet of glucose, sodium, and other minerals in a powder to be dissolved in water.6
The World Health Organization and UNICEF recommend that children with diarrhea take zinc supplements for 10-14 days alongside ORS.7 This report focuses on the evidence for the effectiveness of ORS without zinc supplementation. You can see our report on adding zinc to standard ORS here.
Does the program have strong evidence of effectiveness?
Our impression is that it is widely accepted that ORS is effective at reducing mortality due to diarrhea.8 Due to the lack of randomized controlled trials in community settings, we are uncertain about the magnitude of the effect in those contexts. Below, we discuss the evidence for the effect of ORS on mortality in hospital settings. Our impression is that charities operating in this space will be providing ORS in community settings.
Evidence from hospital settings
The evidence that ORS succeeds at rehydrating children in hospital settings, and is comparably effective to intravenous rehydration, appears to be reasonably strong. Because of its effectiveness in rehydrating children, we would guess that ORS is highly effective at reducing mortality due to diarrhea in hospital settings.
A 2006 Cochrane review (17 trials, 1,811 participants)9 compares oral rehydration therapy with intravenous rehydration therapy in hospitals. It concludes that oral rehydration therapy is comparably effective to intravenous therapy at rehydrating children.10 ORS had a statistically significantly greater chance (4% risk difference, 95% CI 1 to 7) of failing to rehydrate11 than intravenous rehydration therapy.12 The authors conclude this difference was not clinically important.13 15 of the trials were randomized and two were quasi-randomized. The authors note that the trials varied in methodology and quality.14 We have not yet vetted this review or the individual studies included in the review.
How cost-effective is the program?
Based on a cost-effectiveness model we put together in June 2017 and updated with our most recent moral weights as of February 2021, we estimate that ORS is slightly below the range of cost-effectiveness of the opportunities that we expect to direct marginal donations to as of 2021 (about 10x cash or higher);15 however, it is close enough to that range that we believe additional information may change our view. We are highly uncertain about several key inputs in this model, which are dependent on charity-specific information; this model is merely meant to be illustrative of the potential cost-effectiveness of an ORS program. The key assumptions in our CEA are in the following footnote.16
Note that our cost-effectiveness analyses are simplified models that do not take into account a number of factors.17
There are limitations to this kind of cost-effectiveness analysis, and we believe that cost-effectiveness estimates such as these should not be taken literally, due to the significant uncertainty around them. We provide these estimates (a) for comparative purposes and (b) because working on them helps us ensure that we are thinking through as many of the relevant issues as possible.
A number of uncertainties remain that could substantially affect this cost-effectiveness analysis, such as:
- Magnitude of impact of ORS on mortality in community settings: We have not yet comprehensively reviewed the relevant literature on this question. Due to the lack of high quality randomized evidence on the effect of ORS at reducing mortality in community settings, we are uncertain about the magnitude of the expected effect. We use an estimate of a ~93% reduction in mortality from the most frequently cited meta-analysis we have found, and discount it to account for low evidence quality (discussion in this footnote18 ).
- Magnitude of increases in ORS coverage attributable to past ORS programs: We are uncertain about the likely counterfactual ORS coverage rates in areas that have been the target of ORS programs.
- Relative impact of future work: Are future projects likely to be more, less, or similarly cost-effective as past projects?
Organizations that implement this program
We have not conducted a comprehensive search for charities implementing ORS programs. Based on some initial discussions with charities working in this area, we believe there may be room for more funding to support this intervention.
Focus of further investigation
If we were considering recommending a charity working on this program, some questions we may ask as part of further investigation include:
- How does the quality of ORS treatment in a particular charity's context compare to the quality of treatments provided in ORS studies?
- Is the quality of treatment likely to be lower for interventions in which caregivers administer ORS rather than community health workers?
- Does the timing, treatment frequency, and dosage of ORS treatment change its effectiveness?
- Is ORS similarly effective in homes without access to safe drinking water?
- Is there additional information that we could gather to better estimate the magnitude of the mortality effect of ORS?
We searched the Cochrane database for evidence linking ORS to reduced mortality, conducted a brief literature review, and constructed a cost-effectiveness analysis.
|Diarrhea and Pneumonia Working Group 2016 report, Progress over a Decade of Zinc and ORS Scale-up||Source (archive)|
|GiveWell, Cost-effectiveness analysis, 2020, Version 2||Source|
|GiveWell, Zinc/ORS CEA, 2021||Source|
|GiveWell, Zinc/ORS moral weights, 2021||Source|
|Gregorio et al. 2016||Source (archive)|
|Hartling et al. 2006||Source (archive)|
|Image of ORS packet||Source|
|Kumar, Kumar, and Datta 1987||Source (archive)|
|Lives Saved Tool sources 2010||Source (archive)|
|Millions Saved - ORS case study 2007||Source|
|Munos, Walker, and Black 2010||Source (archive)|
|Rahaman et al. 1979||Source (archive)|
|Victora et al. 2000||Source (archive)|
|Walker et al. 2013||Source|
|WHO - Diarrhoeal disease 2017||Source (archive)|
|WHO, Oral Rehydration Salts 2006 report||Source (archive)|
|WHO/UNICEF Joint Statement - Clinical Management of Acute Diarrhoea 2004||Source (archive)|