Using Dried Blood Spots to Quantitatively Detect Anti-SARS-CoV-2 IgG Antibodies by ELISA: A Validation Study.

SARS-CoV-2 serological testing is useful to determine seroprevalence, epidemiological trends, and the extent of transmission. The collection and transport of serum samples can be logistically challenging, especially in remote underserved areas. Dried blood spots (DBSs) would allow easier sample collection and logistical handling compared with standard serum collection, particularly for extensive and repeated SARS-CoV-2 serosurveys. We evaluated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the IgG ELISA (Wantai, Beijing, China) using DBSs against sera for the quantitative detection of SARS-CoV-2 IgG antibody. The IgG ELISA was used to test paired sera and DBSs obtained from individuals with recent virologically confirmed COVID-19 illness and banked paired sera and DBSs collected before the COVID-19 pandemic. We found that 100/100 (100%) seropositive samples were positive using DBSs, and 193/194 (99%) seronegative samples were negative using DBSs. Compared with sera, the DBS method had a 100% sensitivity, 99% specificity, 99% PPV, and 100% NPV. Use of DBSs for SARS-CoV-2 household or population serosurveys may be considered in situations with limitations in sample collection, shipment, and storage.

Envelope-dimer epitope-like broadly protective antibodies against dengue in children following natural infection and vaccination.

Cross-reactive antibodies (Abs) to epitopes that span envelope proteins on the virion surface are hypothesized to protect against dengue. Here, we measured Abs targeting the quaternary envelope dimer epitope (EDE) as well as neutralizing and binding Abs and evaluate their association with dengue virus (DENV) infection, vaccine response, and disease outcome in dengue vaccinated and unvaccinated children (n=252) within a longitudinal cohort in Cebu, Philippines (n=2,996). Abs targeting EDE were prevalent and strongly associated with broad neutralization of DENV1-4 in those with baseline multitypic immunity. Subsequent natural infection and vaccination boosted EDE-like, neutralizing, and binding Abs. EDE-like Abs were associated with reduced dengue risk and mediated the protective effect of binding and neutralizing Abs on symptomatic and severe dengue. Thus, Abs targeting quaternary epitopes help explain broad cross protection in those with multiple prior DENV exposures, making them useful for evaluation and development of future vaccines and therapeutics.

Care seeking for childhood illnesses in rural Mtwara, south-east Tanzania: a mixed methods study.

BACKGROUND: Care seeking was assessed in preparation for a study of the health impact of novel design houses in rural Mtwara, Tanzania. METHODS: A total of 578 residents of 60 villages participated in this mixed-methods study from April to August 2020. Among them, 550 participated in a healthcare-seeking survey, 17 in in-depth interviews and 28 in key informant interviews. RESULTS: The decision to seek care was based on symptom severity (95.4% [370]). Caregivers first visited non-allopathic healthcare providers or were treated at home, which led to delays in seeking care at healthcare facilities. More than one-third (36.0% [140]) of respondents took >12 h seeking care at healthcare facilities. The majority (73.0% [282]) visited healthcare facilities, whereas around one-fifth (21.0% [80]) sought care at drug stores. Treatment costs deterred respondents from visiting healthcare facilities (61.4% [338]). Only 10 (3.6%) of the households surveyed reported that they were covered by health insurance. CONCLUSIONS: Quality of care, related to institutional factors, impacts timely care seeking for childhood illnesses in Mtwara, Tanzania. Ensuring accessibility of facilities is therefore not sufficient.

Dengue virus IgG and serotype-specific neutralizing antibody titers measured with standard and mature viruses are associated with protection.

Recent work demonstrates the limitations of the standard dengue virus (DENV) neutralization assay to predict protection against dengue. We perform studies to compare how a commercial IgG ELISA, envelope domain III (EDIII) or non-structural protein 1 (NS1) binding antibodies, and titers from plaque reduction neutralization tests (PRNTs) using reference standard and clinical mature viruses are associated with dengue disease. Healthy children (n = 1,206) in Cebu, Philippines were followed for 5 years. High ELISA values (≥3) were associated with reduced dengue probability relative to naïve children (3% vs. 10%, p = 0.008), but antibody binding EDIII or NS1 from each serotype had no association. High standard and mature geometric mean PRNT titers were associated with reduced dengue disease overall (p < 0.01), and high DENV2 and DENV3 titers in both assays provided protection against the matched serotype (p < 0.02). However, while 52% of dengue cases had standard virus PRNT titers > 100, only 2% of cases had mature virus PRNT titers > 100 (p < 0.001), indicating a lower, more consistent threshold for protection. Each assay may be useful for different purposes as correlates of protection in population and vaccine trials.

Effect of single-dose, live, attenuated dengue vaccine in children with or without previous dengue on risk of subsequent, virologically confirmed dengue in Cebu, the Philippines: a longitudinal, prospective, population-based cohort study.

BACKGROUND: A three-dose dengue vaccine (CYD-TDV) was licensed for use in children aged 9 years and older starting in 2015 in several dengue-endemic countries. In 2016, the Philippine Department of Health implemented a dengue vaccination programme, which was discontinued because of safety concerns. We assessed the relative risk of developing virologically confirmed dengue among children who did or did not receive a single dose of CYD-TDV by previous dengue virus (DENV) infections at baseline classified as none, one, and two or more infections. METHODS: In this longitudinal, prospective, population-based cohort study, we enrolled healthy children (aged 9-14 years) residing in Bogo or Balamban, Cebu, Philippines, between May 2, and June 2, 2017, before a mass dengue vaccination campaign, via the Rural Health Unit in Bogo and three Rural Health Units in Balamban. We collected demographic information and sera for baseline DENV serostatus and conducted active surveillance for acute febrile illness. Children who developed acute febrile illness were identified, clinical data were collected, and blood was drawn for confirmation of dengue by RT-PCR. The primary outcome was the relative risk of developing virologically confirmed dengue among children who received or did not receive a single dose of CYD-TDV by DENV serostatus at baseline. FINDINGS: A single dose of CYD-TDV did not confer protection against virologically confirmed dengue in children who had none or one previous DENV infection at baseline. One dose conferred significant protection against hospital admission for virologically confirmed dengue among participants who had two or more previous DENV infections at baseline during the first 3 years (70%, 95% CI 20-88; p=0·017) and the entire follow-up period (67%, 19-87; p=0·016). INTERPRETATION: The risk of developing virologically confirmed dengue after a single dose of CYD-TDV varied by baseline DENV serostatus. Since the study assessed the effect of only a single dose, the findings cannot inform decisions on vaccination by public health officers. However, the findings have implications for children who receive an incomplete vaccination regimen and these results should prompt more detailed analyses in future trials on dengue vaccines. FUNDING: The Philippine Department of Health, Hanako Foundation, WHO, Swedish International Development Cooperation Agency, International Vaccine Institute, University of North Carolina, and US National Institute of Allergy and Infectious Diseases.

Dengue.

Dengue, caused by four closely related viruses, is a growing global public health concern, with outbreaks capable of overwhelming health-care systems and disrupting economies. Dengue is endemic in more than 100 countries across tropical and subtropical regions worldwide, and the expanding range of the mosquito vector, affected in part by climate change, increases risk in new areas such as Spain, Portugal, and the southern USA, while emerging evidence points to silent epidemics in Africa. Substantial advances in our understanding of the virus, immune responses, and disease progression have been made within the past decade. Novel interventions have emerged, including partially effective vaccines and innovative mosquito control strategies, although a reliable immune correlate of protection remains a challenge for the assessment of vaccines. These developments mark the beginning of a new era in dengue prevention and control, offering promise in addressing this pressing global health issue.

Prospective observational studies to provide confidence in the protection conferred by newer generation, inactivated oral cholera vaccines: a proposal.

Inactivated oral cholera vaccines (OCVs) are a cornerstone of international efforts to control cholera, and are currently deployed from a global stockpile for the control of epidemics and endemic hotspots, as well as for humanitarian emergencies. One inactivated OCV (with tradenames Shanchol™ and Euvichol-Plus™) is used in the stockpile, but the number of available doses is inadequate to meet the rapidly rising demand for OCVs from countries affected by cholera. Newer, simplified inactivated OCVs under development offer the possibilities of lower expense and higher production yields, and could expand the stockpile. However, their clinical development is made complex because placebo-controlled randomised trials of OCV efficacy are no longer ethically permissible and because the serum vibriocidal antibodies used to measure OCV responses are not correlates of OCV protection against cholera. Here, we propose an observational study design with features to enhance methodological rigor to provide credible evidence of protection against cholera by these newer vaccines.

Understanding reticence to occupy free, novel-design homes: A qualitative study in Mtwara, Southeast Tanzania.

INTRODUCTION: The population of Africa set to reach 2 billion by 2050. There is therefore great demand for housing across the continent. Research on modified novel designs for housing is a priority to ensure that these homes are not sites of infection for diseases transmission such as malaria. One trial to assess the protection afforded by novel design houses is underway in Mtwara Region, southeastern Tanzania. After constructing 110 of such homes across 60 villages, project staff encountered a certain reticence of the target population to occupy the homes and were faced with accusations of having nefarious intentions. This article explores these accusations, their impacts on home occupancy and lessons for future housing studies. METHODS: This qualitative study drew on in-depth interviews and focus group discussions with ten occupants of the intervention homes, six community leaders and a further 24 community members. Interviews were recorded, transcribed verbatim and translated to English for qualitative content analysis. RESULTS: In communities around the Star Homes, during construction and handover, project staff were widely associated with 'Freemasons', a term used to practices, secrecy, and other conspiracy theories in rural Tanzania. These connections were attributed to other community members and explained in terms of knowledge deficit or envy, with others hoping to be allocated the home. The stories were embedded in assumptions of reciprocity and suspicions about study motives, linked to limited experience of research. The relationship between the accusations of freemasonry and reticence to occupy the houses was not straightforward, with project staff or relatives playing a role in decisions. The stakes were high, because the recipients of Star Homes were the poorest families in targeted communities. CONCLUSION: The results indicate the need for long-term and proactive community engagement, which focuses on building relationships and providing information through recognizable voices and formats. Given the stakes at play in housing interventions, research teams should be prepared for the social upheaval the provision of free new housing can cause.

High transmission of endemic human coronaviruses before and during the COVID-19 pandemic in adolescents in Cebu, Philippines.

Background: SARS-CoV-2, the causative agent of COVID-19, is a betacoronavirus belonging to the same genus as endemic human coronaviruses (hCoVs) OC43 and HKU1 and is distinct from alpha hCoVs 229E and NL63. In a study of adolescents in the Philippines, we evaluated the seroprevalence to hCoVs, whether pre-pandemic hCoV immunity modulated subsequent risk of SARS-CoV-2 infection, and if SARS-CoV-2 infection affected the transmission of the hCoVs. Methods: From 499 samples collected in 2021 and screened by SARS-CoV-2 receptor binding domain (RBD) enzyme-linked immunosorbent assay (ELISA), we randomly selected 59 SARS-CoV-2 negative and 61 positive individuals for further serological evaluation. We measured RBD and spike antibodies to the four hCoVs and SARS-CoV-2 by ELISA in samples from the same participants collected pre-pandemic (2018-2019) and mid-pandemic (2021), before COVID-19 vaccination. Results: We observed over 72% seropositivity to the four hCoVs pre-pandemic. Binding antibodies increased with age to 229E and OC43, suggesting endemic circulation, while immunity was flat across ages for HKU1 and NL63. During the COVID-19 pandemic, antibody level increased significantly to the RBDs of OC43, NL63, and 229E and spikes of all four hCoVs in both SARS-CoV-2 negative and positive adolescents. Those aged 12-15 years old in 2021 had higher antibodies to RBD and spike of OC43, NL63, and 229E than adolescents the same age in 2019, further demonstrating intense transmission of the hCoVs during the pandemic. Conclusions: We observe a limited impact of the COVID-19 pandemic on endemic hCoV transmission. This study provides insight into co-circulation of hCoVs and SARS-CoV-2.

Studying the health benefits of improved housing in rural Tanzania: challenges and progress.

Millions of affordable healthy homes are needed for the rapidly expanding population of sub-Saharan Africa. This enormous challenge is an opportunity to address pervasive health issues linked to housing, where diseases that most impact children-malaria, diarrhoea and respiratory tract infections-are often acquired. A pilot project in northern Tanzania demonstrated the potential of novel house designs to reduce infectious disease transmission in homes. To conduct a randomized controlled trial of one novel-design house, the research team moved to the southeast of the country. This article describes the challenges experienced during the construction and initial evaluation of the novel house.

Dengue algorithms integrated into the IMCI guidelines: An updated assessment in five Southeast-Asian countries.

BACKGROUND: Dengue is not included explicitly in the WHO Integrated Management of Childhood Illness (IMCI) algorithm. However, the assessment, classification and management of dengue has been incorporated into several IMCI country adaptations. We aimed to evaluate the dengue algorithms incorporated into IMCI guidelines and discuss the need for harmonization, including an extension of the age range for IMCI. METHODS: This study included three steps. First, we investigated dengue algorithms incorporated into five Southeast-Asian (Myanmar, Philippines, Vietnam, Indonesia, Cambodia) country IMCI guidelines through a desk-based analysis. Second, we conducted an expert survey to elicit opinions regarding the integration of dengue and extension of the age range in IMCI. Third, we compared our findings with data from a large multicentric prospective study on acute febrile illness. RESULTS: We found considerable heterogeneity between the country specific IMCI guidelines in the dengue algorithms as well as classification schemes. Most guidelines did not differentiate between diagnostic algorithms for the detection of dengue versus other febrile illness, and warning signs for progression to severe dengue. Our expert survey resulted in a consensus to further integrate dengue in IMCI and extend the age range for IMCI guidelines beyond 5 years of age. Most of the interviewees responded that their country had a stand-alone clinical guideline for dengue, which was not integrated into the IMCI approach and considered laboratory testing for dengue necessary on day three of consecutive fever. Using data from a large multicentric study of children 5-15 years of age, we could confirm that the likelihood of dengue increased with consecutive fever days. However, a significant proportion of children (36%) would be missed if laboratory testing was only offered on the third consecutive day of fever. CONCLUSIONS: This study supports the extension of the IMCI age range beyond 5 years of age as well as the inclusion of dengue relevant content in the algorithm. Because of the challenge of distinguishing dengue from other febrile illnesses, simple laboratory testing (e.g., full blood count) should be offered at an early stage during the course of the illness. Testing only children with consecutive fever over 3 days may lead to an underdiagnosis of dengue among those with acute febrile illness in children 5-15 years of age. In addition, specific laboratory testing for dengue should be made available to peripheral health facilities.

Vaccine clinical trials in low- and middle-income countries: a brief review of standard, newer and proposed approaches.

INTRODUCTION: Vaccine clinical trials are necessary in low- and middle-income countries (LMICs) because new vaccine candidates are developed against diseases found mainly in these settings, the results of trials done in industrialized countries may not be generalizable to LMICs and more institutions in middle-income countries are producing vaccines for use in LMICs. AREAS COVERED: We searched PubMed and conducted a narrative review on standard, newer and proposed approaches toward obtaining data supportive for vaccine licensure, with a special focus in LMICs. EXPERT OPINION: Of the vaccine trials done worldwide, only a small proportion is conducted in LMICs, but this is likely to increase as more research experience and infrastructure is developed. At present, the majority of vaccine trials follows the standard paradigm of fixed phase 1 to 3 trials, the latter with clinical endpoints, or immunobridging studies when a valid immunocorrelate of vaccine protection exists. Other study designs may help facilitate the generation of data toward licensure of and recommendations for needed vaccines. Increased international collaboration is needed for local capacity building and regulatory oversight to ensure that all studies are conducted under good clinical practice.

Assessing the impact of a novel house design on the incidence of malaria in children in rural Africa: study protocol for a household-cluster randomized controlled superiority trial.

BACKGROUND: Traditional rural housing in hot, humid regions of sub-Saharan Africa usually consists of single-level, poorly ventilated dwellings. Houses are mostly poorly screened against malaria mosquitoes and limited airflow discourages the use of bednets resulting in high indoor transmission. This study aims to determine whether living in a novel design house with elevated bedrooms and permeable screened walls reduces malaria, respiratory tract infections, and diarrhoea among children in rural Tanzania. METHODS/STUDY DESIGN: This is a household-randomized, controlled study in 60 villages in Mtwara, Tanzania. A total of 550 households are randomly selected, 110 of which are allocated a novel design house and 440 households continue to reside in traditional houses. A dynamic cohort of about 1650 children under 13 years will be enrolled and followed for 3 years, approximately 330 living in novel design houses and 1320 in traditional rural houses. The primary endpoint is the incidence of malaria; secondary endpoints are incidences of acute respiratory tract infections and diarrhoea diseases detected by passive and active surveillance. Exposure to malaria vectors will be assessed using light traps in all study houses. Structural, economic, and social science studies will assess the durability, cost-effectiveness, and acceptability of the new houses compared with traditional housing. Environmental data will be collected indoors and outdoors in study homes to assess the differences between house typologies. DISCUSSION: This is the first randomized controlled trial to assess the protective efficacy of a new house design targeting malaria in sub-Saharan Africa. The findings of this study could influence the future construction of homes in hot and humid zones of Africa. TRIAL REGISTRATION: ClinicalTrials.gov NCT04529434 . Registered on August 27, 2020.

Evaluating improved inactivated oral cholera vaccines for use in ending endemic cholera by 2030: opportunities and challenges.

Cholera causes substantial morbidity and mortality in the world's poorest populations. For nearly a decade, an inactivated oral cholera vaccine (OCV) stockpile has been available to control and prevent outbreaks. In 2017, WHO launched a bold global initiative to reduce mortality from cholera by 90% by 2030, a cornerstone of which is deployment of OCVs from the global stockpile. The current production of OCVs for the stockpile falls well short of the doses needed to accomplish this goal. Besides efforts to enlist additional manufacturers of the current OCVs in the stockpile, inclusion of new-generation inactivated OCVs already in clinical development might offer advantages of enlarged production, improved performance, simplified logistics, and reduced costs. However, logistical, scientific, and ethical barriers make conventional, randomised, phase 3 clinical efficacy trials towards licensure of such new-generation OCVs problematic. The serum vibriocidal antibody response, the traditional immunological surrogate of protection against cholera, is imperfect for use as a standalone outcome. In this Personal View, we describe the need for new thinking on approaches for licensure and recommendations for new-generation inactivated OCVs, and suggest a pathway based on a sequential combination of immunogenicity and effectiveness observational studies.

Novel Assay to Measure Seroprevalence of Zika Virus in the Philippines.

Zika virus (ZIKV) is a member of the Flaviviridae family, which includes other clinically notable viruses such as the 4 dengue virus serotypes (DENV-1-4). Distinguishing DENVs from ZIKV using the established serologic assays widely used for monitoring DENV transmission is difficult because of antibody cross-reactivity between these closely related flaviviruses. We describe a modified and improved recombinant envelope domain III-based serologic assay for detecting ZIKV type-specific antibodies in regions with endemic DENV transmission. When the assay was used to measure ZIKV seroprevalence in 2017 among children 9-14 years of age living in a region of the Philippines with endemic DENV transmission, we observed a ZIKV seroprevalence of 18%. Investigators should consider using the ZIKV envelope domain III-based assay, which is simple and readily adaptable for use in standard clinical and public health laboratories, to assess ZIKV seroprevalence in areas with endemic DENV transmission.

Effectiveness of a single-dose mass dengue vaccination in Cebu, Philippines: A case-control study.

BACKGROUND: Dengue fever is an important public health problem in the Philippines. In April 2016, the Department of Health launched a three-dose school based dengue vaccination program of nine- to fourteen-year-old children in three regions with the highest number of dengue cases using CYD-TDV (Dengvaxia, Sanofi Pasteur). In July 2017, a community-based dengue vaccination program was implemented in Cebu province. The program was discontinued in December 2017 amidst public controversy, after the first dose had been administered. We assessed the effectiveness of a single dose of CYD-TDV against hospitalized virologically confirmed dengue (VCD). METHODS: We conducted a case-control study in Cebu province following the dengue mass vaccination. Children who were nine to fourteen years of age during the mass vaccination and subsequently admitted to any of four participating public hospitals with suspected dengue were enrolled in the study as cases. Blood for RT-PCR and clinical and socio-demographic information were obtained. To estimate the level of vaccine protection, vaccination status was compared between children with hospitalized virologically confirmed dengue and controls of the same six-year age-group as the cases, matched on sex, neighborhood and time of occurrence of cases. FINDINGS: We enrolled 490 cases and 980 controls. Receipt of one dose of CYD-TDV was associated with 26% (95 % CI, -2 to 47%; p = 0 0675) overall protection against hospitalized virologically confirmed dengue and 51% (95 % CI, 23 to 68; p = 0 0016) protection against dengue with warning signs. INTERPRETATION: A single dose of CYD-TDV given to nine to fourteen-year-old children through a community-based mass vaccination program conferred protection against dengue with warning signs and severe dengue but we were unable to conclude on protection against milder illness.

Assessment of Vaccine Herd Protection: Lessons Learned From Cholera and Typhoid Vaccine Trials.

Vaccine herd protection is the extension of the defense conferred by immunization beyond the vaccinated to unvaccinated persons in a population, as well as the enhancement of the protection among the vaccinated, due to vaccination of the surrounding population. Vaccine herd protection has traditionally been inferred from observations of disease trends after inclusion of a vaccine in national immunization schedules. Rather than awaiting outcomes of widescale vaccine deployment, earlier-stage evaluation of vaccine herd protection during trials or mass vaccination projects could help inform policy decisions about potential vaccine introduction. We describe the components, influencing factors, and implications of vaccine herd protection and discuss various methods for assessing herd protection, using examples from cholera and typhoid vaccine studies.

Licensed and Recommended Inactivated Oral CholeraVaccines: From Development to Innovative Deployment.

Cholera is a disease of poverty and occurs where there is a lack of access to clean water and adequate sanitation. Since improved water supply and sanitation infrastructure cannot be implemented immediately in many high-risk areas, vaccination against cholera is an important additional tool for prevention and control. We describe the development of licensed and recommended inactivated oral cholera vaccines (OCVs), including the results of safety, efficacy and effectiveness studies and the creation of the global OCV stockpile. Over the years, the public health strategy for oral cholera vaccination has broadened-from purely pre-emptive use to reactive deployment to help control outbreaks. Limited supplies of OCV doses continues to be an important problem. We discuss various innovative dosing and delivery approaches that have been assessed and implemented and evidence of herd protection conferred by OCVs. We expect that the demand for OCVs will continue to increase in the coming years across many countries.

What is the yield of malaria reactive case detection in the Greater Mekong Sub-region? A review of published data and meta-analysis.

BACKGROUND: Reactive malaria case detection involves the screening of those in contact with index cases and is used in countries in the Greater Mekong Sub-region. The yield of reactive case detection, defined here as the percentage of positive malaria cases among potential contacts who were screened, was assessed. METHODS: A literature search was conducted on PubMed to identify studies on reactive case detection in the Greater Mekong Sub-region. Eligible published articles were reviewed and pooled estimates from the studies were calculated, by type of malaria test used. RESULTS: Eighty-five publications were retrieved, of which 8 (9.4%) eligible articles were included in the analysis. The yield from reactive case detection ranged from 0.1 to 4.2%, with higher rates from PCR testing compared with microscopy and/or rapid diagnostic test. The overall yield from microscopy and/or rapid diagnostic test was 0.56% (95% CI 0.31-0.88%), while that from PCR was 2.35% (95% CI 1.19-3.87%). The two studies comparing different target groups showed higher yield from co-workers/co-travellers, compared with household contacts. CONCLUSION: In low malaria transmission settings, the effectiveness of reactive case detection is diminishing. In the Greater Mekong Sub-region, modifying reactive case detection from household contacts to co-workers/co-travellers and from testing to presumptive treatment of targeted contacts, could increase the impact of this approach.