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The CIDRZ Research Repository serves as an open-access archive for peer-reviewed publications, conference papers, and other scholarly outputs from CIDRZ researchers. Our goal is to promote the dissemination of knowledge and support evidence-based public health initiatives.
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Item Evaluation of plasma anti-CS3 and anti-LTB IgG avidity among Zambian children vaccinated with ETVAX.(2026) Mubanga C; Mubanga M; Chilyabanyama ON; Phiri M; Chisenga CC; Glashoff RH; Chilengi RBACKGROUND: Enterotoxigenic Escherichia coli (ETEC) remains a major cause of diarrheal disease in low- and middle-income countries (LMICs). To curb ETEC related diarrhoea, several candidate vaccines are in development, with ETVAX® being the most advanced. Although immunogenicity studies have primarily focused on measuring antibody titres, assessing antibody avidity offers additional valuable insight into antibody quality and immune maturity. This study assessed anti-CS3 and anti-LTB IgG avidity in Zambian children to better understand vaccine-induced antibody responses in an endemic setting. METHODS: Children aged 6-23 months (n = 60) received three quarter-doses of ETVAX® with dmLT adjuvant on days 1, 14, and 90. Plasma samples collected at baseline prior to the first vaccination (Day 1; V1), seven days after the second dose (Day 22; V5), and seven days after the third dose (Day 97; V7) were analysed by limiting antigen dilution ELISA to calculate avidity indices (AI). Naïve classification was performed using titre-based thresholds (20th percentile of baseline titres) and avidity-defined naivety (AI < 0.5). Receiver operating characteristic (ROC) analysis was used to evaluate the discriminatory performance of avidity indices against titre-defined naïve status. RESULTS: Baseline avidity was detectable for both CS3 and LTB, consistent with prior natural exposure. Mean CS3 IgG avidity decreased from 0.7 at baseline to 0.6 after the third dose (p < 0.001), while LTB IgG avidity showed transient decreases but no net gain. Naïve classification at baseline revealed that 9/60 children had titres but low avidity (functional naivety), and 6/60 had waned titres but high avidity. Only one child was naïve by both criteria for CS3, and none for LTB. ROC analysis demonstrated moderate discrimination for CS3 (AUC = 0.65; optimal cut-off AI = 0.36) but poor discrimination for LTB (AUC = 0.30). CONCLUSION: In this endemic population, ETVAX® induced strong antibody titres but minimal changes in avidity over time, with notable inter-individual variability. ROC analysis highlighted context-specific limitations in using avidity to discriminate immune maturity. Together, these findings suggest that while antibody avidity may provide complementary information on antibody quality, its interpretation should be cautious and considered alongside antibody titres in endemic settings.Item Association between hepatitis B co-infection and elevated liver stiffness among HIV-infected adults in Lusaka, Zambia.(2016-Nov) Vinikoor MJ; Mulenga L; Siyunda A; Musukuma K; Chilengi R; Moore CB; Chi BH; Davies MA; Egger M; Wandeler GOBJECTIVE: To describe liver disease epidemiology among HIV-infected individuals in Zambia. METHODS: We recruited HIV-infected adults (≥18 years) at antiretroviral therapy initiation at two facilities in Lusaka. Using vibration controlled transient elastography, we assessed liver stiffness, a surrogate for fibrosis/cirrhosis, and analysed liver stiffness measurements (LSM) according to established thresholds (>7.0 kPa for significant fibrosis and >11.0 kPa for cirrhosis). All participants underwent standardised screening for potential causes of liver disease including chronic hepatitis B (HBV) and C virus co-infection, herbal medicine, and alcohol use. We used multivariable logistic regression to identify factors associated with elevated liver stiffness. RESULTS: Among 798 HIV-infected patients, 651 had a valid LSM (median age, 34 years; 53% female). HBV co-infection (12%) and alcohol use disorders (41%) were common and hepatitis C virus co-infection (<1%) was rare. According to LSM, 75 (12%) had significant fibrosis and 13 (2%) had cirrhosis. In multivariable analysis, HBV co-infection as well as male sex, increased age and WHO clinical stage 3 or 4 were independently associated with LSM >7.0 kPa (all P < 0.05). HBV co-infection was the only independent risk factor for LSM >11.0 kPa. Among HIV-HBV patients, those with elevated ALT and HBV viral load were more likely to have significant liver fibrosis than patients with normal markers of HBV activity. CONCLUSIONS: HBV co-infection was the most important risk factor for liver fibrosis and cirrhosis and should be diagnosed early in HIV care to optimise treatment outcomes.Item Marketing of breast-milk substitutes in Zambia: evaluation of compliance to the international regulatory code.(2018-Mar-01) Funduluka P; Bosomprah S; Chilengi R; Mugode RH; Bwembya PA; Mudenda BBACKGROUND: We sought to assess the level of non-compliance with the International Code of Marketing breast-milk substitutes (BMS) and/or Statutory Instrument (SI) Number 48 of 2006 of the Laws of Zambia in two suburbs, Kalingalinga and Chelstone, in Zambia. METHODS: This was a cross sectional survey. Shop owners (80), health workers (8) and mothers (214) were interviewed. BMS labels and advertisements (62) were observed. The primary outcome was mean non-compliance defined as the number of article violations divided by the total 'obtainable' violations. The score ranges from 0 to 1 with 0 representing no violations in all the articles and one representing violations in all the articles. RESULTS: A total of 62 BMS were assessed. The mean non-compliance score by manufacturers in terms of violations in labelling of BMS was 0.33 (SD = 0.28; 95% CI: 0.26, 0.40). These violations were mainly due to labels containing pictures or graphics representing an infant. 80 shops were also assessed with mean non-compliance score in respect of violations in tie-in-sales, special display, and contact with mothers at the shop estimated as 0.14 (SD = 0.14; 95% CI: 0.11, 0.18). CONCLUSIONS: Non-compliance with the Code and/or the local SI is high after 10 years of domesticating the Code.Item Immunogenicity and safety of two monovalent rotavirus vaccines, ROTAVAC® and ROTAVAC 5D® in Zambian infants.(2021-Jun-16) Chilengi R; Mwila-Kazimbaya K; Chirwa M; Sukwa N; Chipeta C; Velu RM; Katanekwa N; Babji S; Kang G; McNeal MM; Meyer N; Gompana G; Hazra S; Tang Y; Flores J; Bhat N; Rathi NBACKGROUND AND AIMS: ROTAVAC® (frozen formulation stored at -20 °C) and ROTAVAC 5D® (liquid formulation stable at 2-8 °C) are rotavirus vaccines derived from the 116E human neonatal rotavirus strain, developed and licensed in India. This study evaluated and compared the safety and immunogenicity of these vaccines in an infant population in Zambia. METHODS: We conducted a phase 2b, open-label, randomized, controlled trial wherein 450 infants 6 to 8 weeks of age were randomized equally to receive three doses of ROTAVAC or ROTAVAC 5D, or two doses of ROTARIX®. Study vaccines were administered concomitantly with routine immunizations. Blood samples were collected pre-vaccination and 28 days after the last dose. Serum anti-rotavirus IgA antibodies were measured by ELISA, with WC3 and 89-12 rotavirus strains as viral lysates in the assays. The primary analysis was to assess non-inferiority of ROTAVAC 5D to ROTAVAC in terms of the geometric mean concentration (GMC) of serum IgA (WC3) antibodies. Seroresponse and seropositivity were also determined. Safety was evaluated as occurrence of immediate, solicited, unsolicited, and serious adverse events after each dose. RESULTS: The study evaluated 388 infants in the per-protocol population. All three vaccines were well tolerated and immunogenic. The post-vaccination GMCs were 14.0 U/mL (95% CI: 10.4, 18.8) and 18.1 U/mL (95% CI: 13.7, 24.0) for the ROTAVAC and ROTAVAC 5D groups, respectively, yielding a ratio of 1.3 (95% CI: 0.9, 1.9), thus meeting the pre-set non-inferiority criteria. Solicited and unsolicited adverse events were similar across all study arms. No death or intussusception case was reported during study period. CONCLUSIONS: Among Zambian infants, both ROTAVAC and ROTAVAC 5D were well tolerated and the immunogenicity of ROTAVAC 5D was non-inferior to that of ROTAVAC. These results are consistent with those observed in licensure trials in India and support use of these vaccines across wider geographical areas.Item Present or Absent: Risks and protective factors of sudden infant death syndrome (SIDS) in the Zambian context.(2025-May-13) Zulu EM; Mwananyanda L; Pieciak RC; Forman LS; Shah J; Heeren T; Gill CJ; Chilengi R; Payne-Lohman B; Duffy CR; Osei-Poku G; Thea DM; Wa Somwe S; Herlihy JMBACKGROUND: Despite a reduction in Sudden Unexplained Infant Death (SUID) in high-income countries, the incidence of SUID and the prevalence of its risk and protective factors remain poorly understood in Zambia due to limited research. The aim of our study was to describe the infant sleep positions and sleep environments in an urban Zambian population to gain a better understanding of the modifiable risk factors for SUID. METHODS: Data from the Zambian Infant Cohort Study (ZICS), a prospective birth cohort, were collected to describe infant sleep practices in Chawama, a densely populated peri-urban community in Lusaka, Zambia. During the 20-week study visit a structured questionnaire was administered to obtain data about the sleeping and environmental risks associated with SUID. RESULTS: Data were collected from 596 caregivers and 605 infants. Only 6.4% of caregivers did attain an education beyond secondary school, and a significant proportion of infants (20.2%) had low birth weights, with 10.7% of infants confirmed by ultrasound as preterm. Furthermore, 96.5% of infants were placed to sleep on their side or in a prone position, and 98.2% of infants shared a sleep surface with their caregiver. Breastfeeding, a protective factor, was highly prevalent, with 90.2% of infants receiving some form of breastfeeding at the 24-week visit. CONCLUSION: The results of this study show that both modifiable (bed-sharing and prone sleep position) and non-modifiable risk factors (low birthweight and prematurity) of SUID are prevalent in this low socioeconomic setting in Zambia. Public health strategies to prevent SUID will need to be innovative and culturally congruent in addressing modifiable risks, such as bedsharing, in settings where there is a lack of space. TRIAL REGISTRATION: Trial number: 1R01HD094650.Item Mosquito-Borne Viral Pathogens Detected in Zambia: A Systematic Review.(2021-Aug-10) Velu RM; Kwenda G; Libonda L; Chisenga CC; Flavien BN; Chilyabanyama ON; Simunyandi M; Bosomprah S; Sande NC; Changula K; Muleya W; Mburu MM; Mubemba B; Chitanga S; Tembo J; Bates M; Kapata N; Orba Y; Kajihara M; Takada A; Sawa H; Chilengi R; Simulundu EEmerging and re-emerging mosquito-borne viral diseases are a threat to global health. This systematic review aimed to investigate the available evidence of mosquito-borne viral pathogens reported in Zambia. A search of literature was conducted in PubMed and Google Scholar for articles published from 1 January 1930 to 30 June 2020 using a combination of keywords. Eight mosquito-borne viruses belonging to three families,Item Engagement of ethics and regulatory authorities on human infection studies: Proceedings of an engagement workshop in Zambia.(2021) Kunda-Ng'andu EM; Simuyandi M; Kapulu M; Chirwa-Chobe M; Mwanyungwi-Chinganya H; Mwale S; Chilengi R; Sharma AHuman infection studies (HIS) have generally been used as a tool in the pathway for vaccine development in high income settings. Over the last decade, this model has been implemented in LMICs with the aim of accelerating development of next generation vaccines that would perform better in these settings. However, in most LMICs, the ethics and regulatory framework for the conduct of these studies are not in place. In Zambia, these studies are yet to be conducted and thus we conducted a stakeholder engagement workshop in October 2019. We engaged with bioethicists, regulatory authority officials, and scientists from within Zambia and other African countries to anticipate and address foreseeable ethical and regulatory issues when conducting HIS in Zambia for the first time. The workshop largely focused on sensitizing the stakeholders on the benefits of these studies with the following main points for consideration on the implementation of these studies in Zambia: need for in-country legal framework and guidelines; need for adequate informed consent based on comprehensive understanding of the concept of HIS and study requirements; and requirements for heightened vigilance to assure participant safety including good ethical and clinical practice with regulatory, ethical, data safety, and community oversight. Additionally, the workshop emphasized the need for rigorous health screening prior to enrolment; suitable infrastructure for containment; and personnel to provide appropriate treatment including emergency resuscitation and evacuation if indicated. Specific recommendations included compensation for burden of participation; access to care and provision for study related injury (e.g. no-fault insurance); and withdrawal and exit procedures to preserve individual and community safety. Finally, the meeting concluded that researchers should actively engage key gate keepers including civic leaders such as parliamentarians, universities, researchers, potential participants and laypersons to avoid circulation of misinformation.Item Contrasting Epidemiology of Cholera in Bangladesh and Africa.(2021-Dec-20) Sack DA; Debes AK; Ateudjieu J; Bwire G; Ali M; Ngwa MC; Mwaba J; Chilengi R; Orach CC; Boru W; Mohamed AA; Ram M; George CM; Stine OCIn Bangladesh and West Bengal cholera is seasonal, transmission occurs consistently annually. By contrast, in most African countries, cholera has inconsistent seasonal patterns and long periods without obvious transmission. Transmission patterns in Africa occur during intermittent outbreaks followed by elimination of that genetic lineage. Later another outbreak may occur because of reintroduction of new or evolved lineages from adjacent areas, often by human travelers. These then subsequently undergo subsequent elimination. The frequent elimination and reintroduction has several implications when planning for cholera's elimination including: a) reconsidering concepts of definition of elimination, b) stress on rapid detection and response to outbreaks, c) more effective use of oral cholera vaccine and WASH, d) need to readjust estimates of disease burden for Africa, e) re-examination of water as a reservoir for maintaining endemicity in Africa. This paper reviews major features of cholera's epidemiology in African countries which appear different from the Ganges Delta.Item Effect of HIV status and retinol on immunogenicity to oral cholera vaccine in adult population living in an endemic area of Lukanga Swamps, Zambia.(2021) Luchen CC; Mwaba J; Ng'ombe H; Alabi PIO; Simuyandi M; Chilyabanyama ON; Hatyoka LM; Mubanga C; Bosomprah S; Chilengi R; Chisenga CCBACKGROUND: We set out to assess the impact of human immunodeficiency virus (HIV) and micronutrient deficiency as indicated by serum retinol levels on the immune responses to Oral Cholera Vaccine (Shanchol™) in a cohort of participants in Lukanga Swamps, Zambia. Cholera remains endemic in Zambia with vaccines being the only effective preventive measures. However, the effect of these vaccines on populations living with HIV has not been widely documented. METHODS: HIV testing and confirmation was done using the Alere Determine™ HIV-1/2 and Uni-Gold™ kits while vibriocidal antibody assay was applied for vaccine immunogenicity. Serum retinol analysis was assessed by Shimadzu Prominence HCT-2010 High Performance Liquid Chromatography (HPLC). The primary outcome was log transformed geometric mean titre. RESULTS: From 47 participants screened for HIV, 51% (24) tested positive. There was a statistically significant reduction in Ogawa geometric mean ratio (GMR) by 67% (GMR = 0.33; 95% CI: -0.15, 0.76; p-value = 0.009) attributable to HIV positivity with a non-significant reduction in Inaba GMR by about 50% due to HIV positivity. When doubling of retinol levels modelled, GMR reduction against Ogawa were non-significant but that against Inaba resulted in a significant reduction in geometric mean titer (GMT) (GMT-0.33, C.I 0.16-0.66, p-value 0.002). At 1000copies/ml viral load cut off and 350 cells/μl CD4 counts, Ogawa GMT was two times higher 11.16 (95%CI: 8.20-15.19) versus 6.06 (95%CI: 4.04-9.10) in low viremia participants, and three times higher in above threshold CD4 count participants; 24.81 (95%CI: 18.94-32.50) versus 7.07 (95%CI: 5.22-9.58). CONCLUSION: Our results show that while Shanchol™ is immunogenic in both HIV+/- individuals, HIV + participants responded poorly. Viral load and CD4 count affected vaccine immunogenicity. More research is required for detailed understanding of this in order to appropriately inform policy and practice. DOI: 10.1371/journal.pone.0260552Item Immunogenicity and waning immunity from the oral cholera vaccine (Shanchol™) in adults residing in Lukanga Swamps of Zambia.(2022) Ng Ombe H; Simuyandi M; Mwaba J; Luchen CC; Alabi P; Chilyabanyama ON; Mubanga C; Hatyoka LM; Muchimba M; Bosomprah S; Chilengi R; Kwenda G; Chisenga CCINTRODUCTION: In cholera endemic areas, the periodicity of cholera outbreaks remains unpredictable, making it difficult to organize preventive efforts. Lack of data on duration of protection conferred by oral cholera vaccines further makes it difficult to determine when to deploy preemptive vaccination. We report on the immunogenicity and waning of immunity to Shanchol™ in Lukanga Swamps. METHODS: We enrolled a cohort of 223 participants aged between 18 and 65 years old from whom serum samples were collected at baseline, day 28 before administration of the second dose, and consecutively at 6, 12, 24, 30, 36, and 48 months. Vibriocidal antibody titres were measured and expressed as geometric mean titres. Box plots and 95% CI were computed at each visit for both Inaba and Ogawa. Seroconversion was defined as a four fold or greater increase in antibody titres compared to baseline titres. RESULTS: Overall, seroconversion against V. cholerae Inaba and Ogawa after 1st dose was 35/134 (26%) and 34/134 (25%) respectively. We observed a statistical difference in seroconversion between the two subgroups of baseline titres (low <80 and high ≥80) for both Inaba (p = 0.02) and Ogawa (p<0.0001). From a baseline of 13.58, anti-Ogawa GMT increased to 21.95 after the first dose, but rapidly waned to 14.52, 13.13, and 12.78 at months 6, 12 and 24 respectively, and then increased to 13.21, 18.67 and 23.65 at months 30, 36 and 48 respectively. A similar trend was observed for anti-Inaba GMT across the same time points. CONCLUSION: We found that Shanchol™ was immunogenic in our study population and that vibriocidal antibodies may not be a good marker for long-term immunity. The observed rise in titres after 36 months suggests natural exposure, and this may be a critical time window opening for natural transmission in an endemic areas. We recommend re-vaccination at this time point in high risk areas.