Deworming drugs for soil-transmitted intestinal worms in children: effects on nutritional indicators, haemoglobin and school performance

undefinedDeworming programmes may have no effect on average weight, haemoglobin,or cognitive ability. There is not enough evidence to know if deworming improves school attendance.






Researchers in The Cochrane Collaboration conducted a review of the effects of school - based deworming programmes on children’s health, ability to learn, and school attendance. After searching for relevant studies, they identified 41 randomized trials enrolling 65,168 children. 

What are deworming programmes and how might they work?

The World Health Organization (WHO) currently recommends treating all school children at regular intervals with deworming drugs in areas where intestinal helminth infection is common. 

Deworming drugs are known to be effective at curing an individual child with worms. Heavy infections can make children feel unwell, and may contribute to anaemia and malnutrition. 

Deworming programmes are often promoted on the basis that as they treat the worms, they will improve health and enable children to attend school and perform well.

Alternative strategies to these deworming programmes could be to test children prior to treatment, or to improve nutrition, water quality, and sanitation. Deworming programmes may be relatively cheap, but confident investment can only be made with reliable evidence that they work.

What does the research say ?

Deworming programmes that treat all school children at regular intervals for more than one year found that: 

  • They may have no effect on average weight gain.
  • They may have no effect on haemoglobin.
  • They may have no effect on cognitive ability.
  • There is not enough evidence to know if deworming improves school attendance.
  • The Cochrane Review also included trials which only gave a single dose of deworming drugs, and trials which followed children for less than one year.

The Cochrane Review also included trials which only gave a single dose of deworming drugs, and trials which followed children for less than one year. 


How much confidence can I have in these results?

The evidence for no effect on health outcomes (weight and anaemia) is of low quality, due to problems with the trial methods and inconsistency between the results of different studies. The evidence for little or no effect on cognitive ability and school attendance is also of low or very low quality. It is unlikely that deworming programmes would impact on these outcomes in the absence of an effect on weight or haemoglobin.

Can the results of the research be applied to my setting?

Deworming programmes have not demonstrated consistent benefits in high, medium, or low worm prevalence settings.

Three trials from 15 years ago suggested important effects on weight gain, but trials published since then have not confirmed these findings.

The effects of school deworming programmes in areas where worm infection is common

This table provides more detail about what happens when school children are routinely treated with deworming drugs at regular intervals, and are followed up for more than one year, as this provides the best evaluation of what current policy aims to achieve. The Cochrane Review also includes: a) trials which screened children for infection prior to treatment; b) trials which only gave a single dose of deworming drugs, and c) trials which followed children up for less than one year. These numbers are based on the results of the research, when available. The quality of evidence is either ranked as high, moderate, low, or very low. The higher the quality, the more certain we are about what will happen.




No deworming programme

Deworming programme
(95% CI)

No. of children

Quality of

Mean weight gain



Only one of five studies found a significant benefit on weight gain.


(5 studies)


Mean haemoglobin (g/dL)

The mean haemoglobin in the control groups ranged from 9 to 10 g/dL

The mean haemoglobin with deworming was 0.0 g/dL higher (0.08 g/dL lower to 0.08 g/dL higher)


(2 studies)


Cognitive ability 
(test scores)


These two studies assessed multiple cognitive tests and neither study found a benefit with deworming


(2 studies)


School attendance (%)

The mean school attendance in the control group was 66.3%

The mean school attendance with deworming was 5% higher (0.5% lower to 10.5% higher)


(1 study)     

Very low



This summary is based on the following systematic review:

David C Taylor-Robinson1,*, Nicola Maayan2, Karla Soares-Weiser2, Sarah Donegan1, Paul Garner1

Liverpool School of Tropical Medicine, International Health Group, Liverpool, Merseyside, UK
Enhance Reviews Ltd, Wantage, UK

Deworming drugs for soil-transmitted intestinal worms in children: effects on nutritional indicators, haemoglobin and school performance. Cochrane Database of Systematic Reviews 2012, Issue 11. Art. No.: CD000371.

To read the full review please follow this link: DOI: 10.1002/14651858.CD000371.pub5.

Published:11 JUL 2012 updated 14 NOV 2012

The main soil-transmitted worms are roundworms, hookworms, and whipworms. Infections are common in tropical and subtropical areas, particularly in children from low-income areas where there is inadequate sanitation, overcrowding, low levels of education, and lack of access to health care. These infections sometimes cause malnutrition, poor growth, and anaemia in children, and some experts believe they cause poor performance at school. While improved sanitation and hygiene are likely to be helpful, drugs can also be used. In one approach, individuals found to be infected on screening are treated. Evidence from these trials suggests this probably improves weight and may improve haemoglobin values, but the evidence base is small. In another approach, currently recommended by the WHO, and much more extensively investigated, all school children are treated. In trials that follow up children after a single dose of deworming, and after multiple doses with follow up for over a year, we do not know if these programmes have an effect on weight, height, school attendance, or school performance; they may have little or no effect on haemoglobin or cognition.

One trial of a million children examined death and was completed in 2005 but the authors have not yet published the results.