Table 1 Summary of findings from 15 studies meeting the inclusion criteria of the systematic review pertaining to undernutrition and re-infection with soil-transmitted helminths

6- to 8-year-old children

i) Multi-micronutrient biscuits fortified with iron, zinc, iodine and vitamin A given on 5 days per week for 4 months. Albendazole (400 mg, single dose) at baseline

Primary: i) Moderate-to-weak positive effect on the reduction of the infection intensity of all intestinal helminth species in children taking 'fortified biscuits and albendazole’ versus 'albendazole alone’

ii) Multi-micronutrient biscuits and placebo, identical looking to albendazole

Secondary: Moderate-to-weak positive effect on growth and cognition in children receiving fortified biscuits

iii) Non-fortified, identical looking biscuits and albendazole at baseline

iv) Non-fortified, identical looking biscuits and albendazole placebo

6- to 8-year-old children

i) Multi-micronutrient biscuits fortified with iron, zinc, iodine and vitamin A given on 5 days per week for 4 months. Albendazole (400 mg, single dose) at baseline

Primary: i) Strong positive effect on the reduction of the prevalence of all intestinal helminth species in children taking 'fortified biscuits and albendazole’ versus 'albendazole alone’

ii) Multi-micronutrient biscuits and placebo, identical looking to albendazole

Secondary: Strong positive effect on reducing anaemia, zinc and iodine deficiencies in children receiving fortified biscuits

iii) Non-fortified, identical looking biscuits and albendazole at baseline

iv) Non-fortified, identical looking biscuits and albendazole placebo

7- to 15-year-old children

i) Albendazole (400 mg) given to all study participants on 2 consecutive days at baseline

Primary: i) Moderate-to-weak effects on the reduction of the prevalence of A. lumbricoides in children taking 'iron only’ and 'multi-micronutrients only’ versus 'placebo’. Negative effect on the reduction of the prevalence of A. lumbricoides in children taking 'iron with multi-micronutrients’ versus 'placebo’

ii) Multi-micronutrient tablet fortified with vitamin A, B₁, B₂, B₆, B₁₂, C, D and E, niacin, folic acid, zinc, iodine, copper and selenium every school day for 10 months. Ferrous dextran tablet (equivalent to 60 mg of elemental iron) every school day for 10 months

ii) Moderate-to-weak positive effect on the reduction of the infection intensity of A. lumbricoides in children taking 'iron only’ versus 'placebo’. Negative effects on the reduction of the infection intensity of A. lumbricoides in children taking 'iron with multi-micronutrients’ and 'multi-micronutrients only’ versus 'placebo’

iii) Multi-micronutrient tablet and placebo iron tablet

iv) Placebo multi-micronutrient tablet and ferrous dextran tablet

v) Placebo multi-micronutrient tablet and placebo iron tablet

6- to 15-month-old children

i) Vitamin A (given as 20,000 IU of retinol for children <1 year and 45,000 IU for children >1 year) every 2 months for 1 year. Zinc methionine (equivalent to 20 mg of elemental zinc)

Primary: i) Strong positive effect on the reduction of the prevalence of A. lumbricoides in children taking 'zinc alone’ versus 'placebo’. Negative effects on the reduction of the prevalence of A. lumbricoides in children taking ' vitamin A with zinc’ and 'vitamin A alone’ versus placebo

ii) Zinc methionine only

Secondary: i) A combination of vitamin A and zinc had a moderate-to-weak positive effect on the reduction of A. lumbricoides infection duration and a strong positive effect on the reduction of A. lumbricoides-associated diarrhoea

iii) Vitamin A only

iv) Placebo

5- to 15-month-old children

i) Vitamin A (given as 20,000 IU of retinol for children <1 year and 45,000 IU for children >1 year) every 2 months for 15 months

Secondary: i) Strong positive effect on the increase of interleukin 4 (IL-4) levels in vitamin A supplemented children versus placebo

ii) Placebo

8- to 18-year-old children

i) Albendazole (600 mg, single dose) given to all children at baseline and 4 weeks after baseline (600 mg, single dose) if child was still infected

Primary: i) For children taking 'multi-micronutrients’ versus 'placebo’, moderate-to-weak positive effects on the reduction of the prevalence of A. lumbricoides and hookworm and negative effect on the reduction of the prevalence of T. trichiura

ii) Multi-micronutrient tablet fortified with vitamin A, B₁, B₂, B₆, B₁₂, C, D and E, niacin, folic acid, zinc, iodine, copper, iron and selenium every school day for 11 months

ii) For children taking 'multi-micronutrients’ versus 'placebo’, moderate-to-weak positive effects on the reduction of the infection intensity of all intestinal helminth species

iii) Placebo, identical looking to the multi-micronutrient tablet

4- to 15-year-old children (n = 200) and 16- to 63-year-old adolescents and adults (n = 129)

i) Albendazole (400 mg, once a day for 3 consecutive days) at baseline for all individuals and if any individual was still infected between 3 and 6 months after baseline, re-treatment (400 mg, single dose) was given

Primary: i) For children taking 'iron’ versus 'placebo’, moderate-to-weak positive effects on the reduction of the prevalence of all intestinal helminth species and in the reduction of infection intensity of hookworm. Negative effects on the reduction of infection intensity of A. lumbricoides and T. trichiura

ii) Ferrous dextran tablet (equivalent to 60 mg of elemental iron) twice weekly for 12 months

ii) For adolescents/adults taking 'iron’ versus 'placebo’, strong positive effects on the reduction of the prevalence of A. lumbricoides and T. trichiura and moderate-to-weak positive effect on the reduction of the prevalence of hookworm. In terms of infection intensity reduction, negative effects for A. lumbricoides and T. trichiura and moderate-to-weak positive effect for hookworm

iii) Placebo identical looking to the ferrous dextran tablet

65- to 95-month-old children

i) Mebendazole (100 mg twice daily for 3 days) at baseline for all individuals

Primary: i) Negative effect on the reduction of the prevalence of A. lumbricoides and T. trichiura (mentioned collectively) in children taking 'zinc’ versus 'placebo’

ii) Tablet containing zinc (10 mg) and vitamin A, E, C, B₆, B₁₂ and D, folic acid, thiamin, riboflavin, niacinamide, pantothenic acid, iron, copper, iodine, selenium, chromium and magnesium given on every school day for 120–150 days

iii) Different colour-coded tablets, containing all the micronutrients, except for zinc, found in the intervention tablet

<5-year-old children

i) Cycle 1: albendazole (200–400 mg depending on age, single dose) to all children >12 months at baseline. Children followed up for 9 months

Primary: i) Strong positive effect on the reduction of A. lumbricoides infection intensity at the end of cycle 1 in children with higher height-for-age (HAZ) versus their peers with lower HAZ score

ii) Strong positive effect on the reduction of hookworm infection intensity at the end of cycle 2 in children with higher height-for-age (HAZ) versus their peers with lower HAZ score

ii) Cycle 2: albendazole (200–400 mg depending on age, single dose) to all children >12 months at baseline. Children who remained infected with at least 1 soil-transmitted helminth were given another single dose of albendazole. Children followed up for 6 months

7- to 12-year-old children

i) Albendazole (400 mg, once a day for 3 consecutive days) for all children at baseline. Children followed for 6 months to investigate predictors of re-infection

Primary: i) Moderate-to-positive effects on the reduction of the prevalence of A. lumbricoides, T. trichiura and hookworm (mentioned collectively) in non-stunted children versus stunted children

12- to 60-month-old children

i) One-off supplementation with vitamin A (60 mg retinol) given by the Ministry of Health

Primary: i) Moderate-to-weak positive effect on the reduction of the A. lumbricoides prevalence and infection intensity in vitamin A-supplemented children versus non-supplemented ones

ii) Albendazole (400 mg, single dose) for all children at baseline. Children were followed at 3 and 5 months post-treatment

1- to 10-year-old children

i) Mebendazole (triple doses at baseline and repeated 15 days after). Children were followed at 1 year post-treatment

Primary: i) Moderate-to-weak positive effect on the reduction of the prevalence of A. lumbricoides and T. trichiura (mentioned collectively with other helminths, such as Hymenolepsis nana and S. stercoralis) in eutrophic children versus undernourished children

6- to 11-year-old children

i) Oxantel/pyrantel (20 mg/kg) monthly for 12 months for all children. Children were followed at 8 months after the 12 months of treatment

Primary: i) Strong positive effect on the reduction of the prevalence of A. lumbricoides in children >10th percentile for height versus children ≤10th percentile for height

4- to 10-year-old children

i) Mebendazole (500 mg, single dose) was given to all children at baseline. Children were followed at the end of 12 months, when they were given pyrantel pamoate (11 mg/kg) and 48-hour worm expulsions were performed

Primary: i) Moderate-to-weak positive effect on the reduction of the infection intensity of A. lumbricoides in the best-nourished children versus children with reduced growth indicators

6- to 11-year-old children

i) Oxantel/pyrantel (20 mg/kg) monthly for 12 months for all children. Children were followed at the end of the 12 months of treatment

Secondary: i) Strong positive effect on an increase of anti-Ascaris IgE levels in well-nourished children versus under-nourished children