Gershom Chongwe

Background: Shigella spp. is a leading cause of moderate-to-severe diarrhea and diarrheal mortality in children under five (CU5), globally. Traditional culture-based techniques consistently underestimates its prevalence, particularly in high-burden regions of sub-Saharan Africa. We aimed to generate population-relevant estimates of shigellosis among hospitalized children under five (CU5) in Ndola, Zambia, using a sensitive molecular diagnostic approach. Methods: A prospective, hospital-based surveillance study was conducted at Arthur Davison Children’s Hospital (ADCH) from May 2020 to November 2021. All CU5 admitted with acute diarrhea (≥2 watery stools/day) were eligible. From enrolled children, sociodemographic and clinical data were collected, and stool samples were obtained where possible. Primary detection of Shigella spp./enteroinvasive E. coli (EIEC) was performed using loop-mediated isothermal amplification (LAMP) targeting the conserved ipaH gene. Operational shigellosis case-definition: A child with diarrhea (2 or more watery stools/day) and a stool sample positive for the ipaH gene by LAMP. Prevalence of shigellosis was calculated among children with LAMP-tested samples and weighted to account for all admissions. The incidence of hospitalization was estimated using the district CU5 population denominators. Results: Among 1,685 enrolled children, 950 provided stool samples. LAMP detected ipaH in 186 samples (19.6%;95% CI: 17.1–22.5). The weighted prevalence among all admissions was 19.5% (95% CI: 17.5–21.5) corresponding to 329 cases. The incidence of shigellosis hospitalization was 2.4 (95% CI: 2.2–2.7) per 1,000 person-years. The burden exhibited a distinct age distribution, peaking in children aged 12–23 months, preceded by an evident rise in the number of cases between 6 and 12 months of age. Shigellosis was associated with bloody diarrhea, increased stool frequency, and fever. Pre-admission antibiotic or other medication use was reported in 33% of cases. Conclusions: Shigellosis accounts for a substantial proportion of severe diarrhea requiring hospitalization in Ndola, Zambia. Findings support improved diagnostics, antimicrobial stewardship, and prioritization of Shigella vaccines.

Many children in Zambia miss measles vaccination through routine immunization, while supplementary immunization activities (SIAs) targeting children under five may not reach older under-vaccinated children. School-based vaccination screening and catch-up (SVS) is a recommended strategy to identify and vaccinate these children, but evidence on its implementation and cost in sub-Saharan Africa is limited. We estimated the cost of an SVS pilot for measles vaccination in Zambia to inform implementation and potential scale-up.,We conducted an ingredients-based costing from the Government of Zambia perspective of an SVS pilot in 20 urban schools in Lusaka and rural schools in Masaiti. Costs were estimated under three scenarios: base case (full pilot costs); post-introduction (excluding start-up and technical support); and budgeting (assuming full program integration and excluding start-up, technical support, and Ministry of Health and Education staff costs). One-way and probabilistic sensitivity analyses were conducted. Costs are reported in 2024 USD and Zambian kwacha (ZMW).,Among 3,351 children screened, 215 were identified as measles-rubella (MR) zero-dose and 211 were vaccinated. Total implementation cost was USD 75,886 (ZMW 2,111,157) in the base case. By input, personnel accounted for 70.6% of costs. By SVS activity, coordination and training accounted for 46.8% and 34.0% of total costs, respectively. Costs decreased by 28.3% in the post-introduction and 42.3% in the budgeting scenario. Cost per child screened ranged from USD 13.05–22.65, and per MR zero-dose child vaccinated from USD 208.29–360.70. Coordination time was the most influential parameter.,While costs per child are relatively high, SVS is a targeted strategy that can be used to reach older children who remain unreached by routine immunization programs and SIAs. Efficiency could improve through streamlined documentation, integration with school health activities, and reduced coordination and personnel requirements. Further research should assess its comparative value and cost-effectiveness against other approaches.

School-based vaccination screening is a promising platform to identify and vaccinate older children missed by routine services. In 2024, Zambia’s Ministry of Health and Ministry of Education implemented a pilot school-based vaccination screening and catch-up (SVS) program in 20 schools across one urban and one rural district, supported by our research team. We conducted an explanatory sequential mixed-methods process evaluation to assess reach, fidelity, effectiveness, feasibility, acceptability and sustainability using the Consolidated Framework for Implementation Research and Proctor et al.’s implementation outcomes. Between June–November 2024 we undertook document review, implementation strength assessment surveys, direct observations and in-depth interviews with implementers and caregivers. Quantitative indicators were summarized descriptively, and qualitative data were thematically analyzed and triangulated across components.Of 4,092 enrolled learners, 81.9% were screened and 77.1% presented vaccination cards. Among those screened, 6.4% missed both measles-rubella (MR) doses and 13.7% missed only MR2. Catch-up uptake was high: 98.1% of MR zero-dose learners received MR1 and 95% of those missing MR2 received catch-up vaccination. Key implementation enablers included strong teacher-nurse coordination, high training participation, the perception of schools as convenient and efficient platforms for SVS activities and the flexibility to adapt community sensitization strategies to local contexts. However, operational constraints included transport limitations, short training duration and burdensome documentation.Zambia’s SVS pilot was feasible, acceptable, and implemented with high reach and uptake through school-based measles screening and catch-up. Future scale-up would require a national catch-up policy for children older than 5 years, clear operational guidance, and evidence on costs and sustainability. With these in place, SVS could be integrated into school health programs to reach children missing measles doses.

School vaccination screening (SVS) programs can facilitate catch-up vaccination among children who have missed routine immunization, but assessing vaccination status in school-aged children is challenging because vaccination records are often unavailable and caregiver recall may be unreliable. We conducted a school-based cross-sectional serosurvey nested within an SVS program in Ndola District, Zambia, from March to July 2025 to estimate measles seroprevalence and evaluate the relationship between serology and vaccination status ascertained through vaccination cards and caregiver recall. Caregiver-reported measles-containing vaccine (MCV) history was collected, and dried blood spots were tested for measles IgG antibodies by ELISA; children aged <9 years were additionally tested for rubella IgG antibodies.Of 964 eligible children, 924 (95.8%) participated. Nearly one-third lacked a readable vaccination card, primarily children aged ≥5 years. Based on vaccination cards or caregiver recall, 85.2% had received ≥1 routine MCV dose, while 14.8% had received no routine MCV doses; 72.6% reported at least one MCV dose received outside routine services. Overall measles seroprevalence was 85.6% and was higher among children with vaccination documented by card than caregiver recall. Among children aged <9 years classified by caregiver recall as having received no routine MCV doses, 83.6% were seropositive for both measles and rubella, suggesting misclassification of vaccination status. Screening based on vaccination cards alone would have referred 488 children and identified 69.2% (n=93) of measles-seronegative children requiring catch-up vaccination. Adding caregiver recall reduced referrals to 353 children but identified 53.3% (n=71), while including non-routine doses recall further reduced referrals to 194 children and identified 31.5% (n=42). Caregiver recall was more prone to misclassification than vaccination cards, highlighting the need to balance sensitivity and efficiency when designing SVS strategies. Strengthening vaccination documentation systems and clarifying the role of caregiver recall will be important for optimizing school-based vaccination screening programs.

Residual blood specimens collected at health care facilities provide a low-cost and readily available specimen source to monitor population immunity through serological surveillance compared to more resource-intensive probability-based surveys. Despite concerns about the representativeness of these specimens, there has recently been increased interest in the use of residual specimens, driven by the need for rapid estimates of seroprevalence during outbreaks to inform response and prevention. Although residual specimen collection is a key component of surveillance systems in some settings, there is limited evidence of its implementation in low- and middle-income countries. We conducted a pilot project at three health facilities in two districts in Zambia between September 2021 through July 2022 to demonstrate the feasibility of residual blood specimen collection integrated into the health system to estimate measles seroprevalence. Through this pilot project, we were able to collect residual pediatric and adult specimens but with some modifications needed if residual specimen collection were to be implemented at scale, such as better integration into the routine functioning of laboratories and health facilities. This paper summarizes our experiences designing and implementing this residual blood specimen collection, including the lessons learned and recommendations for collecting residual specimens from hospitals.

Medical male circumcision (MMC) is an established HIV prevention intervention, yet concerns persist that circumcised men may adopt higher-risk sexual behaviours following the procedure. Evidence from observational studies has been inconsistent, partly because many analyses do not adequately distinguish behaviours that occur before circumcision from those that occur afterward. This study assessed the association between MMC and subsequent sexual behaviours while demonstrating how population-based cross-sectional survey data can be adapted to address this temporal challenge. We analysed nationally representative data from the 2024 Zambia Demographic and Health Survey (ZDHS), including men aged 15 - 59 years who reported their circumcision status. Men who had undergone medical circumcision were compared with uncircumcised men using a matched pseudo-cohort framework that reconstructed temporal ordering based on age at circumcision. Propensity score overlap weighting was applied to improve comparability between circumcised and uncircumcised men, and odds ratios were estimated using logistic regression models incorporating overlap weights and accounting for the complex survey design. Sexual behaviour outcomes occurring after circumcision included condom non-use at last sexual intercourse, multiple sexual partners in the past 12 months, self-reported sexually transmitted infection (STI) symptoms, and composite measures of sexual risk behaviour. The analysis included 9,609 men, of whom 33.3% were medically circumcised. MMC was associated with lower odds of condom non-use at last sexual intercourse (adjusted odds ratio [aOR] = 0.75, 95% confidence interval [CI]: 0.67 - 0.85) and lower odds of reporting any sexual risk behaviour (aOR = 0.83, 95% CI: 0.72 - 0.95). No meaningful associations were observed between MMC and reporting multiple sexual partners, self-reported STI symptoms, or higher levels of composite sexual risk behaviour. In this population-based study, MMC was not associated with sexual risk compensation under routine programme conditions within the overlap population defined by the weighting scheme, supporting the behavioural safety of MMC and illustrating the value of explicitly addressing temporality when analysing behavioural outcomes using cross-sectional survey data.

Residual blood specimens collected at health care facilities provide a low-cost and readily available specimen source to monitor population immunity through serological surveillance compared to more resource-intensive probability-based surveys. Despite concerns about the representativeness of these specimens, there has recently been increased interest in the use of residual specimens, driven by the need for rapid estimates of seroprevalence during outbreaks to inform response and prevention. Although residual specimen collection is a key component of surveillance systems in some settings, there is limited evidence of its implementation in low- and middle-income countries. We conducted a pilot project at three health facilities in two districts in Zambia between September 2021 through July 2022 to demonstrate the feasibility of residual blood specimen collection integrated into the health system to estimate measles seroprevalence. Through this pilot project, we were able to collect residual pediatric and adult specimens but with some modifications needed if residual specimen collection were to be implemented at scale, such as better integration into the routine functioning of laboratories and health facilities. This paper summarizes our experiences designing and implementing this residual blood specimen collection, including the lessons learned and recommendations for collecting residual specimens from hospitals.

Post-campaign coverage surveys estimate the proportion of previously unvaccinated children vaccinated during supplementary immunization activities (SIA) but cannot address whether susceptible children seronegative to measles and rubella viruses were vaccinated during the SIA. We conducted a cross-sectional serosurvey nested within the November 2020 measles-rubella SIA in Zambia, systematically sampling children aged 9 months to 5 years at 30 SIA sites in Choma and Ndola Districts. A questionnaire administered to caregivers collected the child’s demographic information and vaccination history. Dried blood spot specimens were collected from child participants and for Immunoglobulin-G antibodies to measles and rubella viruses by enzyme immunoassay. We used the expected vaccination probability by age derived from Demographic and Health Surveys to quantify the value of the immunization campaign, estimating the proportion of children who would not have otherwise received routine MR doses. Among children enrolled with MR vaccination data (N = 2,364), 2,214 (94%) reported at least one routine MR dose before the SIA. We estimate 5.0% [95%CI, 4.2-5.9%] (n = 118/2364) of children would not have otherwise received routine MR dose 1 without the SIA and 23.4% [95%CI, 21.7-25.1] (n = 553/2364) would not have otherwise received routine MR dose 2. Thus, 1 in 3.5 doses were given to an MR un- or under-vaccinated child who may not have received that dose in the absence of an SIA. Eighty-six percent and 90% of children were measles and rubella seropositive before vaccination during the SIA. Thirty-six percent of children with no prior routine MR dose were measles seropositive, while nine percent of children with two prior routine MR doses were measles seronegative. Although children vaccinated during this SIA were highly likely to have previously received routine vaccinations, the SIA reached a considerable number of susceptible children. Monitoring SIA effectiveness and efficiency through standardized metrics and formats is critical for impactful vaccine delivery strategies.

Background: Geographic information systems (GIS) are a promising tool for mapping vaccination coverage and identifying missed communities, yet their use in low- and middle-income countries (LMICs) remains limited. In settings without standardized addresses such as schools or outreach sites, innovative methods are needed to collect and analyse spatial data. Schools offer a unique platform for identifying under-vaccinated children missed by routine or campaign efforts. Methods: During a pilot school vaccination screening program in Zambia, GIS reference maps of health facility catchment areas were developed from hand-drawn sketch maps, catchment area shapefiles, and coordinates of prominent landmarks. These maps were iteratively refined with input from local health staff. In caregiver interviews, data collectors used the maps to identify the child’s zone of residence within the health facility catchment area. Vaccination status was extracted from paper registries used during screening. Geographic heat maps were generated in ArcGIS to visualize under-vaccination by zone. Results: Of 535 children screened across 25 zones, 29% were under-vaccinated. Under-vaccination varied by zone, with clusters of missed children identified, for example, 50% of children in Kabushi Zone 6 were under-vaccinated, compared with much lower rates elsewhere. Conclusions: Pairing school-based vaccination checks with GIS mapping offers a scalable approach to identifying missed communities in LMICs. This method enables spatial analysis without household visits, supporting targeted immunization planning where traditional data systems fall short. However, because the study was limited to children enrolled in five purposively selected schools, out-of-school children and those in other schools were not represented. This selection bias may underestimate the true extent of under-vaccination, and future evaluations should incorporate broader and more representative populations.