Evidence Action's Deworm the World Initiative — 2027 Funding for Nigeria, Kenya, Pakistan (May 2025)

Note: This page summarizes the rationale behind a GiveWell grant to Evidence Action's Deworm the World Initiative. Evidence Action staff reviewed this page prior to publication.

Published: August 2025

The organization

Deworm the World is a program led by Evidence Action, an organization that focuses on scaling up interventions that it believes are cost-effective and evidence-based. Deworm the World provides financial and technical assistance to governments implementing school- and community-based mass drug administration (MDA) to treat soil-transmitted helminths (STH) and schistosomiasis (SCH). We have been supporting Deworm the World since 2014 (see our previous grants in this table). For more information on the type of support Deworm the World provides, see our review of the organization here.

The intervention

Deworming involves treating large numbers of people with parasite-killing drugs: praziquantel kills the parasites that cause schistosomiasis (SCH), while albendazole or mebendazole kills soil-transmitted helminths (STH).1 Treatment is cheap and the side effects of the drugs are believed to be minor; thus, everyone in a given population (sometimes schoolchildren; sometimes the community at large) is treated, without being individually tested for the presence of infections. For more information on how we assess the benefits of mass deworming, see our separate report on deworming.

Deworm the World supports government-run school-based deworming programs. The assistance that Deworm the World provides varies by country, but typically includes:2

• Training: Deworm the World helps design, organize, and pay transport/per diem costs for a "training cascade" where teachers and other government staff learn how to implement a Deworming Day and receive materials necessary for implementation.
• Prevalence surveys: Deworm the World conducts surveys on the prevalence of worm infections to track the impact of deworming MDA over time and refine treatment strategies.
• High-level program planning: Deworm the World assists governments in developing deworming strategy and operational guidelines, including how to adjust treatment strategies based on the results of new prevalence surveys.
• Drug procurement and protocols: Deworm the World assists governments in obtaining drugs, designing drug distribution and tracking processes, and developing adverse event protocols for cases where children react poorly to treatment. Deworm the World does not typically finance any drugs itself, though it made an exception last year in Kenya.3
• Monitoring and evaluation: Deworm the World assists governments in designing or improving their reporting and monitoring systems, and also engages third-party monitors to collect independent data, including coverage surveys.
• Community sensitization and advocacy: Deworm the World supports community sensitization efforts, which aim to raise awareness among local communities about Deworming Day and the benefits of deworming children. Deworm the World also encourages national and large sub-national governments to implement mass school-based deworming programs, through meeting with health and education officials to discuss the benefits of deworming.

A note on our deworming approach

We intend to responsibly reduce our investment in deworming over time. Considering deworming grants has historically required a significant amount of GiveWell staff capacity, and we no longer consider deworming a high-priority intervention area. This is because we do not have high confidence in the cost-effectiveness of continued deworming programming,4 and annual spending on deworming programs is relatively small compared to other programs we support, meaning deworming programs provide comparatively low returns on our capacity. As a result, we intend to exit from deworming programs unless we believe that (a) a child's risk of contracting a worm infection in a given geography is still moderately high, meaning continued investment could still be highly cost-effective and (b) we can provide support with minimal staff capacity. Meeting the second criterion will entail working with grantees - such as Deworm the World - that share our values (including being highly transparent about their goals and any challenges they face), are strong implementing partners, and that have a clear plan for cost-effectively adapting deworming programs based on data about deworming coverage and burden.

The grant

We are recommending continued support for deworming activities in four states in Nigeria, and a final year of support for deworming in Kenya and Khyber Pakhtunkhwa, Pakistan.

The grant approach for each geography is as follows:

• Nigeria: Deworm the World supports deworming in the states of Cross River, Ogun, Oyo, and Rivers.5 These deworming programs are less mature than the program in Kenya and we expect that supporting them at their current scale is still cost-effective, as we believe that children in these states still have a moderate risk of contracting worm infections. We do not expect to support these programs indefinitely, but we're optimistic that we can align with Deworm the World on a reasonable timeline for phasing out support of these programs.
• Kenya: Deworm the World supports the national deworming program in Kenya. Worm prevalence has decreased significantly since Deworm the World first began its support,6 and Deworm the World now intends to either transfer the program to the government at a reduced scale or fundraise to continue supporting the government for a few additional years, if Deworm the World believes it remains cost-effective to do so. This final year of funding is intended to enable Deworm the World to develop a responsible exit strategy.
• Pakistan: Deworm the World supports deworming activities in several provinces in Pakistan, but GiveWell support ended in 2024 for all provinces other than Khyber Pakhtunkhwa due to low estimated cost-effectiveness. We are now phasing out support for Khyber Pakhtunkhwa as well, due to its borderline cost-effectiveness and low return on our capacity. We expect surplus from prior grants to cover program costs in 2027, and we're funding global support costs in this grant because we expect exit activities in 2027 will require higher-level strategy support from Deworm the World's global team.

Budget for grant activities

Kenya: $830,000
This is the amount needed to fill the remaining funding gap for Deworm the World's deworming support in Kenya in 2027. The full program budget is $1.89 million,7 but the funding gap is reduced by surplus from prior years and allocation of some non-GiveWell funding to support this program.8

Note that the 2027 budget is not an exit-specific budget, as Deworm the World requested funds for another year of normal program operations. We are treating this as exit funding because we do not expect to provide further support for the Kenya deworming program beyond this grant, but we have not asked Deworm the World to provide a new exit-specific budget. We expect that in practice Deworm the World may use more of these funds than originally expected on policy and strategy discussions with the government in preparation for exit, and may choose to spend less on MDA-specific activities. We are leaving it to Deworm the World's discretion to determine the highest priority activities to support in 2027.

As of the time of writing, the deworming program aims to treat ~3.5 million children for STH and ~1.2 million for SCH in 2027 (based on current treatment strategies).9 It's possible these treatment targets will change before 2027, for instance, if new prevalence survey results suggest fewer areas require treatment. We plan to stay in touch with Deworm the World about any changes to treatment targets prior to 2027 and their implications for the 2027 budget.

Nigeria: $300,000
Deworm the World expects existing funding commitments to cover the full budget for in-state deworming costs in the four supported states (Cross River, Ogun, Oyo, and Rivers) in 2027, due to local currency depreciation and budgeting adjustments.10 The $300k from this grant will cover the share of Deworm the World's global support costs that we estimate are attributed to support of the Nigeria deworming programs.11 Global support consists of personnel costs for global staff who help guide country-level strategies (including associated costs such as staff travel, offices, and conferences) and external consultancy costs.12

Pakistan: $250,000
As with the Nigeria funding described above, this funding will cover global-level support costs proportional to the budget for Khyber Pakhtunkhwa, Pakistan in 2027. Additional program-level support is not needed due to surplus from previous years' spending.13 Because we do not intend to renew support for this program past 2027, this constitutes GiveWell's exit funding for the program.

Deworm the World may fundraise for continued support for this deworming program, as it is doing with the other provinces in Pakistan where GiveWell support has ended. If it is successful, we expect our funding (both surplus from past grants and the global support funding provided in this grant) would be used to support normal program activities and strategy discussions. We are comfortable with this use of funding because we believe (though with fairly low confidence) that this program would still be at or near our cost-effectiveness bar in 2027,14 since this is a newer program that we don't expect to have achieved large declines in worm prevalence yet.15 If Deworm the World is not successful in fundraising, we expect that our global support funding will be used to assist in the development of an exit strategy for this program. In that scenario, we expect Deworm the World may choose to prioritize using some of the surplus programmatic funds to support exit preparations with the government (such as domestic resource mobilization) in place of some normal program activities.

The case for the grant

Our funding decisions for these programs were guided by the approach described above.

In more detail, we're recommending exit funding in Kenya and Pakistan because:

• Data suggests that worm burden in Kenya has fallen significantly. Deworm the World's most recent prevalence survey found a substantial reduction in STH prevalence compared to baseline: declining from ~32% in 2012 to ~6% in 2021/2022.16 The survey also found very low rates of moderate or heavy intensity worm infections for both STH and SCH, achieving WHO targets for "elimination as a public health problem."17 Given these large declines in worm burden, we are not confident that continued deworming in Kenya would meet our cost-effectiveness bar. Deworm the World shares our view that it is unlikely to be cost-effective to pursue interruption of transmission of worm infections across Kenya,18 so we agreed that Deworm the World would aim to transfer support for a likely smaller deworming program to the Kenyan government or fundraise to support the program for a couple more years.
• We believe providing transition funding through 2027 increases the chances of a successful government handover in Kenya. We do not plan to support any deworming program indefinitely, but as discussed below, we believe there's a risk that worm infections will rebound if treatment stops completely. We think the ideal outcome for areas that have achieved low worm burdens through deworming programs would be for the government to expend a small amount of resources (compared to the cost of an early stage deworming program) on treatment, surveillance, or both, to keep the risk of worm infections low. We think that is more likely to occur if Deworm the World supports the government in developing a strategy for continued treatment and disease surveillance after Deworm the World exits.

  We've selected 2027 as the exit year because Deworm the World is considering conducting another prevalence survey in Kenya in 2026.19 Although the 2021/22 survey found low worm prevalence nationally, some counties still had ≥10% STH prevalence,20 and WHO recommends annual deworming treatment in areas with ≥10% and <20% STH prevalence.21 We think it's very possible a new survey would find lower prevalence in some of those counties, given that they've received several more rounds of deworming MDA. We're providing funding through 2027 so that any post-exit treatment and surveillance strategy that Deworm the World develops with the government can be based on the latest worm burden evidence available. We think providing funding through 2027 would allow enough time for analysis and discussion of the latest survey results with the government.22

• We expect low returns on investment in Pakistan. The deworming program in Khyber Pakhtunkhwa is the least mature program we support (in terms of the number of years it's been running),23 so we expect it would have a relatively long timeline to achieve the disease control targets Deworm the World is aiming for.24 However, even if we assume there have been no reductions in worm prevalence since Deworm the World began supporting the program, this program only barely meets our cost-effectiveness threshold of 10x.25 Additionally, we have found that supporting the deworming program in Pakistan requires comparatively more of our and Deworm the World's capacity than other geographies do. Because of these considerations, we view this program as having a comparatively low return on investment (in terms of cost-effectiveness and our capacity) so we're planning to end our support of the program.

However, we are approving an extension on surplus funds from prior grants to allow Deworm the World to continue supporting the program in 2027 because we believe this final year of support will require minimal staff capacity from us and we expect children in Khyber Pakhtunkhwa may still be at moderate risk of worm infections in 2027. As discussed above, we have also decided to fill the funding gap for global support costs in 2027 (~$250K) so Deworm the World will have the strategic support necessary for either another year of normal program operations or support for developing an exit strategy.

We are recommending continued funding in Nigeria because:

• Continued deworming in Nigeria is likely cost-effective. We have previously estimated the cost-effectiveness of Deworm the World's programming in Nigeria (outside of Lagos state) was 11-15 times that of unconditional cash transfers. While we have not updated our cost-effectiveness analysis as part of this grant investigation, in line with our intention to decrease our staff time investment in deworming programming, we expect the program to continue to be cost-effective because most local government areas in the states that GiveWell supports still have moderate worm prevalence.26 We expect this means both that a greater number of worm infections would happen without our funding, and that worm prevalence could more quickly rebound to higher levels in the absence of further treatment (when compared to lower prevalence settings, such as Kenya).
• Deworm the World has been a strong implementing partner. Deworm the World has been consistently strong on monitoring activities,27 generally achieves high treatment coverage,28 and has been a strong, well-aligned thought partner as we try to adapt our deworming strategy to declining worm prevalence. On the latter, Deworm the World has been working with Lancaster University to pilot a lower cost survey methodology for measuring worm prevalence and forecast when different geographies will reach disease control targets.29 It has also been working with governments to adjust treatment strategies in light of new worm prevalence results to focus on areas with the highest risk of worm infections.30 All together, these qualities give us confidence that we can continue to support Deworm the World's program in Nigeria with minimal GiveWell staff capacity due to our high alignment and trust in Deworm the World as a grantee.

Risks and reservations

Our main reservation about this grant is:

• Potential for a rebound in worm infections in Kenya. Although we're recommending that Deworm the World exit from further support of the deworming program in Kenya in 2027, we are not recommending a cessation of all government-run deworming activities. We hope that some activities will continue post Deworm the World's exit, per the latest WHO guidance for deworming programs in the "maintenance phase". However, if the Kenyan government is unable or unwilling to continue running a small-scale deworming program, there could be a rebound in worm infections. Currently, the worm burden in Kenya is quite low, but it's possible and perhaps probable that children would start getting sick with worm infections again if deworming activities completely stopped after 2027.31

We haven't collected much information on what happens to deworming programs after they stop receiving GiveWell funding, meaning we have limited information to help us assess the likelihood of a successful government handoff. However, we also don't want to be in a position of funding deworming indefinitely, due to the high staff capacity it requires and the difficulty of quantifying the benefits of continued deworming programming.

We are recording this as a reservation about exiting from Kenya, but not Pakistan, because we estimated a significantly higher baseline (pre-deworming) worm burden in Kenya, compared to Pakistan.32 We speculate that the baseline worm burden in each geography serves as an upper limit on the magnitude of a potential rebound in worm infections, if worm burden were to rebound absent continued deworming. While a rebound in worm infections would be a negative outcome in either geography, we think the magnitude of the negative effects could be far greater in Kenya, where the risk of children experiencing moderate to heavy intensity worm infections was much higher at baseline.

Plans for follow up

We intend to have quarterly check-ins with Deworm the World, where we will get updates on:

• High-level news about MDA rounds, such as delays in drug shipments
• Impacts of foreign aid cuts
• Prevalence survey timelines, ethical approvals, and results
• Exit plans or fundraising progress across GiveWell-funded geographies
• The status of deworming programs in places where GiveWell support has ended (e.g. GiveWell support ends in Lagos, Nigeria in 2025)

Internal forecasts

For this grant, we are recording the following forecasts:

Confidence	Prediction	By time	Resolution
70%	GiveWell will provide further funding for Deworm the World-supported deworming programs that are implemented in Nigeria in 2028	By January 31, 2026	-
70%	The 2025 prevalence surveys in Oyo and Ogun will find that most SCH and STH-endemic LGAs still have ≥10% prevalence	By December 2026	-
60%	Deworm the World will still be supporting deworming activities in Pakistan in 2028 (this would count as true if Deworm the World was supporting deworming in Pakistan through non-GW funds or if GW supports another program in Pakistan that allows Deworm the World to continue supporting deworming)	By January 2029	-
65%	Conditional on Deworm the World support ending in 2027 and not being replaced by another partner's support, the Kenyan government will conduct some deworming activities in 2028 with domestic resources. This could include continued MDA rounds and/or surveillance activities.	By January 2029	-
55%	Conditional on Deworm the World support ending in 2027 and not being replaced by another partner's support, the Kenyan government will conduct some deworming activities in 2029 with domestic resources. This could include continued MDA rounds and/or surveillance activities.	By January 2030	-

Our process

This was a fairly light-touch grant review.

• We had discussions with Deworm the World about this grant, exit timelines, and Deworm the World's latest coverage data.
• We conducted a room-for-more-funding analysis to calculate the funding gaps in GiveWell-supported geographies
• We spoke to a Deworm3 researcher about the state of evidence on rebound in worm infections

Sources

Document	Source
Ajjampur et al., Feasibility of interrupting the transmission of soil transmitted helminths: the DeWorm3 community cluster randomised controlled trial in Benin, India, and Malawi, 2025	Source
Evidence Action, 2023 DTW Process Monitoring and Coverage Validation Results	Source
Evidence Action, Deworm the World	Source (archive)
GiveWell, All Content on Evidence Action's Deworm the World Initiative	Source
GiveWell, Combination Deworming (Mass Drug Administration Targeting Both Schistosomiasis and Soil-Transmitted Helminths), 2025	Source
GiveWell, Cost-effectiveness analyses	Source
GiveWell, Evidence Action's Deworm the World — Renewal Grant for Nigeria, Pakistan, Kenya, and India (March 2024)	Source
GiveWell, Evidence Action's Deworm the World Initiative – August 2022 version	Source
GiveWell, Evidence Action's Deworm the World Initiative — Nigeria, Pakistan, and Kenya (January 2023)	Source
GiveWell, February 2023 Worm Burden Adjustment: moderate infection equivalent model	Source
GiveWell, GiveWell's cost-effectiveness analysis for Deworm the World [2024 renewal]	Source
GiveWell, Internal forecasts	Source
GiveWell, Room for more funding analysis for Deworm the World, 2025	Source
Soil-Transmitted Helminths and Schistosomiasis Prevalence Probabilities Using Geostatistical-Based Models in 27 Counties of Kenya	Source
University of Washington, Deworm3	Source (archive)
WHO, Assessing schistosomiasis and soil-transmitted helminthiases control Programmes - Monitoring and evaluation framework, 2024	Source
WHO, Preventive chemotherapy in human helminthiasis, 2006	Source

• 1

  See World Health Organization, Preventive chemotherapy in human helminthiasis, Table 2, p. 10.

• 2

  See our Deworm the World grantee review for more information.

• 3

  Evidence Action, conversation with GiveWell, August 5, 2024 (unpublished).

• 4

  Our cost-effectiveness model assumes that, absent our funding, a child's risk of contracting worm infections would be the same as it was in that geography prior to when our grantees began supporting any deworming MDA. However, we expect that the risk of contracting a worm infection will fall substantially after repeated years of deworming MDA. For example in Kenya, where Deworm the World has been supporting MDA for over 10 years, we've seen an 82% reduction in STH prevalence compared to baseline.

  • "Compared to previous evaluation surveys, the Y9 evaluation survey showed low STH prevalence that significantly reduced after the nine years of chemotherapy (Figure 11). The overall prevalence for any STH reduced by 82.0% (p<0.001) from an initial prevalence of 32.3% to 5.8%, with more than half reduction from the last immediate evaluation survey (i.e., Y6 evaluation)." Soil-Transmitted Helminths and Schistosomiasis Prevalence Probabilities Using Geostatistical-Based Models in 27 Counties of Kenya, 2023, p.14
  • This means that our cost-effectiveness model likely overestimates the cost-effectiveness of continued deworming in Kenya, since we expect far fewer children to be at risk of worm infections now, unless worm prevalence would rebound all the way back to baseline levels absent our funding. We're very uncertain whether that would occur. There is limited evidence to date on the amount of rebound to expect when deworming MDA stops, meaning we do not have a way to quantify the benefits of continued deworming in places where worm prevalence has fallen from baseline.

• 5

  Note that Deworm the World also supports deworming in Lagos state, but 2025 is the last year of GiveWell funding for that geography. We decided in 2024 to not renew funding for Lagos due to low estimated cost-effectiveness, more here.

• 6

  Prevalence surveys have shown significant reductions in STH prevalence in Kenya between 2012 and 2021/2022:

  • "Compared to previous evaluation surveys, the Y9 evaluation survey showed low STH prevalence that significantly reduced after the nine years of chemotherapy (Figure 11). The overall prevalence for any STH reduced by 82.0% (p<0.001) from an initial prevalence of 32.3% to 5.8%" Soil-Transmitted Helminths and Schistosomiasis Prevalence Probabilities Using Geostatistical-Based Models in 27 Counties of Kenya, 2023, p.14

  Prevalence surveys have shown significant reductions in S. haematobium (one species of worm that causes schistosomiasis) prevalence in Kenya between 2012 and 2021/2022. Prevalence of S. mansoni (another species of worm that causes schistosomiasis) has increased slightly, but still remains very low:

  • "Compared to baseline survey, the Y9 evaluation survey showed low S. haematobium prevalence that significantly reduced after the nine years of chemotherapy (Figure 12 panel B). The overall prevalence for S. haematobium reduced by 87.8% (p<0.001) from an initial prevalence of 18.0% to 2.2%. However, S. mansoni prevalence instead has increased non-significantly after the nine years of treatment from initial prevalence of 2.4% to 3.0% (relative increase of 25.0%, p=0.180)." Soil-Transmitted Helminths and Schistosomiasis Prevalence Probabilities Using Geostatistical-Based Models in 27 Counties of Kenya, 2023, p.14

• 7

  At the time of approving this grant, the 2027 program budget was estimated to be:

  • Awareness: $78,750
  • Drugs: $31,500
  • Monitoring and Evaluation: $236,250
  • Policy: $110,250
  • Prevalence Survey: $0
  • Training: $732,375
  • Program Management: $370,125
  • Indirect Costs: $330,750
  • Total: $1,890,000

  Deworm the World, 2024 Room for More Funding Request, Budgets by Activity (unpublished)

• 8

  See the allocation of non-GiveWell funding in our room for more funding calculations.

• 9

  "The strategy for year 3 (2025), mimicks year 1 (2023) and so on, which means that in 2027, we will target approximately 3.2M for STH and 1M for SCH. However, actual targets can also differ closer to the round, depending on treatment plans by the NTD unit, as well as availability of drugs." Deworm the World, 2024 Room for More Funding Request, Budgets by Activity (unpublished)

  • Note that Deworm the World corrected these figures during review of this page to: ~3.5 million children targeted for STH treatment and ~1.2 million targeted for SCH treatment in 2027.

• 10

  "We are not seeking funds in 2027. Existing commitments are expected to cover funding needs due to significant exchange rate depreciation, and adjustments to out-year budgets to better align with implementation plans." See the notes in the Nigeria section of GiveWell, Room for more funding analysis for Deworm the World, 2025

• 11

  See the allocation of global costs in our room for more funding analysis.

  • Cross River: $33,085
  • Ogun: $70,897
  • Oyo: $94,529
  • Rivers: $99,256
  • Total: $297,766
  • Note that GiveWell is not providing funding for Lagos state.

• 12

  On what global support consists of: "Evidence Action's 2024 budget includes ~$1.3M in personnel costs for 10.5 full time equivalent staff members (~20 staff with partial LOE) supporting DTW India, Kenya, Nigeria, and Pakistan and over-arching program leadership. These global staff work closely with country team leadership to set country level strategies that are in line with global guidelines, the changing NTD landscape, and the current DTW strategy. Evidence Action's global support also includes technical consultancy costs with Lancaster's University Centre for Health Informatics, Computing and Statistics (CHICAS) to guide future monitoring and surveillance strategies, specifically using model-based geostatistics in mixed and low prevalence settings. Global costs also include associated costs for global staff (staff travel, office supplies, office rent, conference attendance, IT and professional development)."
  Deworm the World, 2024 Room for More Funding Request, Budgets by Activity (unpublished)

• 13

  "We are not seeking funds for Pakistan KP in 2027. Existing commitments are expected to cover funding needs due to prior year underspend and adjustments to out-year budgets to better align with implementation plans." See the notes in the Pakistan section of GiveWell, Room for more funding analysis for Deworm the World, 2025

• 14

  We currently model the cost-effectiveness of Deworm the World's program in Khyber Pakhtunkhwa at 10 times as cost-effective as unconditional cash transfers.

  Note that a) our cost-effectiveness analyses are simplified models that are highly uncertain, and b) our cost-effectiveness threshold for directing funding to particular programs changes periodically. As of 2025, our bar for directing funding is about 10 times as cost-effective as unconditional cash transfers. See GiveWell’s Cost-Effectiveness Analyses webpage for more information about how we use cost-effectiveness estimates in our grantmaking.

• 15

  Deworm the World began supporting deworming in Khyber Pakhtunkhwa in 2019. Deworm the World, comments during review of this page, June 2025 (unpublished)

  • If a deworming program has succeeded in reducing worm prevalence in a specific geography, we think that, all else equal, the cost-effectiveness of future deworming funding in that area will likely be lower as the underlying disease burden will have fallen. Given the recency of the deworming program in Khyber Pakhtunkhwa, we don't expect there to be substantial declines in worm prevalence that would translate into significantly lower cost-effectiveness by 2027–though this reasoning is speculative and we haven't reviewed recent data on worm prevalence in Khyber Pakhtunkhwa.

• 16

  See: Soil-Transmitted Helminths and Schistosomiasis Prevalence Probabilities Using Geostatistical-Based Models in 27 Counties of Kenya, 2023, p. 31 (Table 11 - column 'STH Combined')
  Based on WHO guidance, when STH prevalence is ≥ 2% and < 10%, preventive chemotherapy (deworming) should be administered once every two years for all at-risk groups.

  • See WHO, Assessing schistosomiasis and soil-transmitted helminthiases control Programmes - Monitoring and evaluation framework, 2024, p. 28 (Table 10)

• 17

  On STH prevalence: The prevalence of moderate to heavy intensity combined STH infections was 1.3% (95%CI: 1.1-1.5) in 2021/2022. Soil-Transmitted Helminths and Schistosomiasis Prevalence Probabilities Using Geostatistical-Based Models in 27 Counties of Kenya, 2023, p. 29 (Table 9 - column 'Prevalence of moderate-heavy infections - Calculated using total children examined as denominator')

  • The WHO states that < 2% prevalence of moderate to heavy intensity STH infections is indicative of achieving elimination as a public health problem. "For soil-transmitted helminthiases and schistosomiasis, EPHP is the elimination of acute morbidity caused by the infection. WHO has identified the following indicators indicative of reaching EPHP:▸ soil-transmitted helminthiases: < 2% prevalence of moderate and heavy intensity infections▸ schistosomiasis: < 1% prevalence of heavy intensity infections" WHO, Assessing schistosomiasis and soil-transmitted helminthiases control Programmes - Monitoring and evaluation framework, 2024, p. viii
  • Viewed together, we think the data suggest Kenya has achieved elimination as a public health problem for STH.

  On SCH prevalence: The prevalence of heavy intensity S. Mansoni infections was 0.3% (95%CI: 0.2-0.4) in 2021/2022. The prevalence of heavy intensity S. haematobium infections was 0.1% (95%CI: 0.1-0.2) in 2021/2022. Soil-Transmitted Helminths and Schistosomiasis Prevalence Probabilities Using Geostatistical-Based Models in 27 Counties of Kenya, 2023, p. 29 (Table 9 - column 'Prevalence of moderate-heavy infections - Calculated using total children examined as denominator')

  • The WHO states that < 1% prevalence of heavy intensity SCH infections is indicative of achieving elimination as a public health problem. "For soil-transmitted helminthiases and schistosomiasis, EPHP is the elimination of acute morbidity caused by the infection. WHO has identified the following indicators indicative of reaching EPHP:▸ soil-transmitted helminthiases: < 2% prevalence of moderate and heavy intensity infections▸ schistosomiasis: < 1% prevalence of heavy intensity infections" WHO, Assessing schistosomiasis and soil-transmitted helminthiases control Programmes - Monitoring and evaluation framework, 2024, p. viii
  • Viewed together, we think the data suggest Kenya has achieved elimination as a public health problem for SCH.

• 18

  "There is also no evidence-based, cost-effective, relatively short to medium-term path to interruption of transmission for national programs…. Eliminating the last remaining cases of infection in a low-prevalence environment becomes exponentially more expensive and may have limited population-level impact." Deworm the World, November 2024 Strategy Addendum (unpublished)

• 19

  Note that at the time of making this grant decision, we believed it was possible that Deworm the World would conduct another survey in 2026. Since that time, we have learned of national data harmonization efforts –pulling together data collected from all prevalence surveys in the past few years–which have made a 2026 survey unnecessary. Instead, Deworm the World may plan for a survey in 2027 or 2028, when more time has passed since the most recent surveys were conducted.

  We still believe it is valuable to provide exit support in 2027 so that Deworm the World could either conduct a new survey with GiveWell funding or assist with planning for a future survey that would take place after GiveWell support ends, as well as provide high level strategy support regarding the role that future surveys could play in Kenya's long term worm control strategy (e.g. the scope and frequency at which these surveys might be cost-effective).

• 20

  See Soil-Transmitted Helminths and Schistosomiasis Prevalence Probabilities Using Geostatistical-Based Models in 27 Counties of Kenya, 2023, p. 23 (Table 2)

• 21

  See WHO, Assessing schistosomiasis and soil-transmitted helminthiases control Programmes - Monitoring and evaluation framework, 2024, p. 28 (Table 10)

• 22

  Note that at the time of making this grant decision, we believed it was possible that Deworm the World would conduct another survey in 2026. Since that time, we have learned of national data harmonization efforts–pulling together data collected from all prevalence surveys in the past few years–which have made a 2026 survey unnecessary. Instead, Deworm the World may plan for a survey in 2027 or 2028, when more time has passed since the most recent surveys were conducted.

  We still believe it is valuable to provide exit support in 2027 so that Deworm the World could either conduct a new survey with GiveWell funding or assist with planning for a future survey that would take place after GiveWell support ends, as well as provide high level strategy support regarding the role that future surveys could play in Kenya's long term worm control strategy (e.g. the scope and frequency at which these surveys might be cost-effective).

• 23

  See GiveWell, Evidence Action's Deworm the World — Renewal Grant for Nigeria, Pakistan, Kenya, and India (March 2024) grant page for an overview of when Deworm the World's programs began in the areas GiveWell has supported.

• 24

  Deworm the World began supporting the deworming program in Khyber Pakhtunkhwa in 2019. Deworm the World's rough timeline for support of deworming programs is as follows:

  • "Phase I lasts approximately 5 years, focusing on establishing the program and achieving over 75% treatment coverage for consecutive years.
  • Phase II continues for another 5 years of high coverage, working to reduce disease prevalence by >50% from baseline and reach <10% prevalence.
  • Phase III typically begins around the 10-year mark, when programs have achieved substantial reductions in prevalence and can transition to surveillance or suspend large-scale treatment when reaching low prevalence across implementation units for STH or sub-implementation units for SCH.
  • The complete timeline spans roughly 10+ years from start to potential scale-down, although duration varies based on local conditions and baseline disease levels."

  Deworm the World, comments during review of this page, June 2025

• 25

  We last estimated the cost-effectiveness of deworming in KP, Pakistan to be 10 times as cost-effective as unconditional cash transfers in 2024, but our model did not account for any changes in worm burden since the time that Deworm the World started supporting KP. In other words, the model assumes worm burden in the absence of our funding would be as high as it was prior to Deworm the World's support.

• 26

  "A prevalence survey conducted in Rivers State in 2023 showed a 70.6% reduction in the mean prevalence rate of STH compared to baseline. Most LGAs now sit between 10% and 20% prevalence."
  Deworm the World, responses to GiveWell questions, March 2025 (unpublished)

  • A prevalence survey was conducted in Cross River state in 2024, and at the time of this writing, the results were in the final stages of review. New prevalence surveys will also be conducted in Ogun and Oyo in 2025/26. We do not currently have any reason to believe that prevalence is declining faster in those states compared to Rivers.

• 27

  As an example, we consider it best practice for coverage surveys to be conducted no more than 2 months after deworming MDA to try to reduce the risk of poor recall. Deworm the World's latest surveys in Nigeria were conducted between 1-6 weeks after MDA.

• 28

  We calculated median coverage for deworming rounds in Nigeria from 2016 to 2022 was 77%, which is above the WHO coverage target for deworming programs of 75%. GiveWell, Deworm the World monitoring summary, 2023 (unpublished)

  • Source for WHO coverage threshold: WHO, Assessing schistosomiasis and soil-transmitted helminthiases control Programmes - Monitoring and evaluation framework, 2024, p. 21 (Table 8)

  Some LGAs in Nigeria had lower coverage in the 2023 deworming rounds, but Deworm the World had reasonable explanations for why (these are generally harder to reach areas, with either difficult terrain and/or large distances between schools) and for how they address lower coverage areas (see below). Deworm the World, responses to GiveWell questions, March 2025 (unpublished)

  "Based on data from coverage surveys, we take various steps to update government planning and implementation of mass drug administrations, depending on the context.

  • For example, if treatment coverage is low in harder-to-reach communities due to difficult terrain or insecurity, during the microplanning process, we help governments identify additional resources to safely reach those communities and deliver treatment.
  • If treatment coverage is low due to low school enrollment, we adapt treatment platforms and engage community drug distributors and other supporting health workers to conduct house-to-house and/or fixed-point distribution alongside school-based distribution facilitated by teachers.
  • We also prioritize working closely with local-level government stakeholders to encourage advocacy and sensitization at the community level to reach children who were previously not treated during mass drug administration rounds." Deworm the World, comments during review of this page, June 2025

• 29

  On new methods for measuring worm prevalence: "In 2021-2022, Evidence Action made a strategic decision to partner with CHICAS [Lancaster University's Center for Health Informatics, Computing, and Statistics] to pilot their new methodology across DTW geographies. This collaboration has enabled Evidence Action to conduct cost-effective, high-quality prevalence surveys at lower administrative units with enhanced precision, leading to updated and more targeted treatment strategies across diverse geographies. This partnership has proven mutually beneficial, with Evidence Action making significant contributions to the development and refinement of CHICAS's approach." Evidence Action, Strategy Addendum, November 2024 (unpublished), p. 9

  On forecasting time to disease control targets: "Based on modeling conducted in partnership with CHICAS, our best guess is that by 2028, 18 out of 27 counties [in Kenya] would have achieved disease control for STH (<2% prevalence); whereas for SCH only 4 out of 27 counties would have reached disease control (<1% prevalence). Therefore, by 2028, the Kenya program will be smaller and will require fewer resources for STH (9 counties with a portion of sub-counties)."

  • "Once the surveys are completed across four states (Oyo and Ogun planned for 2025/6), we will engage in similar modeling as we did in Kenya to better predict # of years required to get to disease control (low prevalence); and should be able to share more on this by end of next year (2026)." Deworm the World, responses to GiveWell questions, March 2025 (unpublished)

• 30

  Deworm the World informed us that some areas in Kenya will now receive deworming treatment every other year rather than annually and some counties have suspended STH treatment, following analysis of the 2021-2022 impact assessment survey results which showed that some areas have reached <2% STH prevalence. Deworm the World, conversation with GiveWell, August 14, 2023 (unpublished)

• 31

  When we say that the worm burden is low, we are making reference to WHO's targets for elimination as a public health problem: "For soil-transmitted helminthiases and schistosomiasis, EPHP is the elimination of acute morbidity caused by the infection. WHO has identified the following indicators indicative of reaching EPHP:▸ soil-transmitted helminthiases: < 2% prevalence of moderate and heavy intensity infections▸ schistosomiasis: < 1% prevalence of heavy intensity infections" WHO, Assessing schistosomiasis and soil-transmitted helminthiases control Programmes - Monitoring and evaluation framework, 2024, p. viii

  • On STH prevalence; "the prevalence of moderate to heavy intensity was 1.3% (95%CI: 1.1-1.5)…The county level prevalence of moderate to heavy intensity of STH infections is shown in Table 10, and it varied from 0% to 8.1% using option 1". Soil-Transmitted Helminths and Schistosomiasis Prevalence Probabilities Using Geostatistical-Based Models in 27 Counties of Kenya, 2023, p. 13
  • On SCH (S. mansoni) prevalence: "prevalence of heavy was 0.3% (95%CI: 0.2-0.4…)the prevalence of moderate to heavy [infections] was 1.6% (95%CI: 1.4-1.8)". Soil-Transmitted Helminths and Schistosomiasis Prevalence Probabilities Using Geostatistical-Based Models in 27 Counties of Kenya, 2023, p. 14
  • On SCH (S. haematobium) prevalence: "the prevalence of light infections for S. haematobium was 1.3% (95%CI: 1.2-1.6)…and the prevalence of heavy was 0.1% (95%CI: 0.1-0.2)". Soil-Transmitted Helminths and Schistosomiasis Prevalence Probabilities Using Geostatistical-Based Models in 27 Counties of Kenya, 2023, p. 14

  On the possibility of resurgence:

  • "Resurgence remains possible when reaching and maintaining disease control, and the risk increases if disease control is not monitored and maintained. However, due to the current lack of evidence, the risk and rate of resurgence over time are unknown." Evidence Action, Strategy Addendum, November 2024 (unpublished)
  • "In the maintenance phase (after EPHP), a low prevalence of infection may still be present. Prevalence is expected to decline progressively, and reducing the frequency of preventive chemotherapy administration may be necessary to maintain programme gains and prevent rebound of infection. Surveillance is undertaken until there is no risk of rebounding of prevalence and intensity of infection." WHO, Assessing schistosomiasis and soil-transmitted helminthiases control Programmes - Monitoring and evaluation framework, 2024, p. 14
  • The Deworm3 study, which among other outcomes tested the prevalence of worm infections in different locations after a two year cessation of deworming, found evidence of increased prevalence of worm infections in some areas and in some age groups compared to the study's baseline. However, we're still unsure how much rebound to expect in the absence of further deworming in GiveWell-supported areas. We don’t know the rate of rebound in different locations in the Deworm3 study, as the midline samples have not yet been analyzed, and we're unsure to what extent rebound in Deworm3 areas might generalize to GiveWell-supported areas. Deworm3, conversation with GiveWell, March 26, 2025 (unpublished).
    • We weren't able to identify the precise findings the Deworm3 study team described to us in their recently published paper reporting on the results of the trial, so we have open questions about our interpretation of the results.

• 32

  Our pre-deworming weighted prevalence estimate for moderate infection equivalents was 5.19% in Kenya and 1.29% in KP, Pakistan. GiveWell, February 2023 Worm Burden Adjustment: moderate infection equivalent model (see tab 'Worm burden synthesis: program adjustments', column G, rows 58 and 65)

  • We weight reported prevalences of moderate and heavy intensity infections for infection intensity to form a unit we call "moderate infection equivalents'. A 'moderate infection equivalent' takes into account the expectation that heavy worm infections lead to more severe morbidity than moderate intensity ones, so that a heavy infection is effectively equivalent in severity to multiple moderate infections.