Diphtheria outbreak in Lao People's Democratic Republic, 2012-2013

Comparison of Diphtheria Cases in Children Before and During the Pandemic Era in Surabaya, Indonesia: A Study of Six-Year Data

Introduction Indonesia has a high incidence of diphtheria, especially in children. Surabaya has become a government regional reference center, as it is the capital of East Java province, which has the highest rate of diphtheria across the 38 regions. The aim of this study is to report our six-year pediatric diphtheria data, focusing on comparisons between before and during the pandemic era. Method This surveillance report was collected from community health centers and hospitals throughout Surabaya from January 1, 2017 to December 31, 2022. Collected data included demographic characteristics, clinical and laboratory aspects, the health centers, immunization history, and management. As per Indonesian guidelines, the diagnosis of diphtheria in this country requires a positive microbiological culture or approval from the National Experts on Diphtheria Committee. Results In total, there were 112 cases, of which 89 were found before the pandemic era. Although the number of cases declined during 2020-2022, the predominant age group, the immunization status, and the most common type of diphtheria remained consistent with pre-pandemic trends. Most cases had incomplete immunization or unimmunized children (67.8%), with the age group of 5-12 years old (44.6%), and with tonsillar diphtheria (83%). The case fatality ratio was 1.8%. Regarding the biovar of Corynebacterium diphtheriae, gravis is the most frequent finding. Conclusion The incidence of diphtheria cases in children in Surabaya was significantly lower during the pandemic. Although immunization coverage was not better, preventive measures during the pandemic may have played a role. Most patients did not have complete immunization histories during the study period, and the predominant type was tonsillar diphtheria. Since the trend in 2021-2022 increased, routine surveillance is essential.

Reaching the unreached through building trust: a mixed-method study on COVID-19 vaccination in rural Lao PDR

INTRODUCTION

The global COVID-19 vaccine rollout has been impacted by socioeconomic disparities and vaccine hesitancy, but few studies examine reasons for changed attitudes. In Lao People's Democratic Republic (Lao PDR), a nationwide government-led initiative was developed in response to COVID-19, focused on community health ownership and trust in primary healthcare. The intervention team including health and governance sectors conducted capacity-building workshops with local staff and community representatives and visited villages for vaccination outreach. This study investigates the impact of this intervention on COVID-19 vaccine acceptance in rural communities.

METHODS

Conducted in Xiengkhuang province, Lao PDR, from December 2022 to February 2023, the study employed a sequential mixed-methods research design. Data on vaccinated individuals from 25 villages were collected from 11 primary healthcare units; pre-post analysis was applied. Qualitative data, gathered through interviews and focus group discussions with villagers, village authorities, health staff and local government (n=102) in six villages, underwent inductive thematic analysis.

RESULTS

First-dose vaccine uptake after the intervention increased significantly (6.9 times). Qualitative analysis identified key reasons for vaccination hesitancy: (1) mistrust due to rumours and past experiences; (2) poor communication and inconsistent messaging and (3) challenges in access for priority groups. Influencing factors during the intervention included (1) effective local-context communication; (2) leveraging existing community structures and influential individuals in a multisectoral approach and (3) increased community motivation through improved satisfaction, ownership and relationships.

CONCLUSION

This study highlights the impact and methods of building trust with unreached populations in health interventions, emphasising locally led solutions. Successful reversal of vaccine hesitancy was achieved by addressing root causes and fostering ownership at community and local government levels through a 'positive approach'. This diverges from conventional supplemental immunisation activities and holds potential for systematically building trust between unreached populations and health systems. Further research could explore the impacts of routine vaccination for sustained improvements in health equity.

Factors associated with hepatitis B vaccination in Laos: findings from the multiple indicator cluster surveys in 2011/12 and 2017

Background

Within Laos, the vaccination coverage rates with the monovalent hepatitis B birth dose vaccine and hepatitis B antigen-containing combination vaccines remain stagnant with 75% and 64%, respectively, in 2021. In this study, we used data from the Multiple Indicator Cluster Surveys to identify possible factors that represent barriers for receiving these childhood vaccinations.

Methods

Data from the Multiple Indicator Cluster Surveys in 2011/12 and 2017 were analysed to examine factors associated with receiving the hepatitis B-containing vaccines using regression modelling. Data analyses were conducted in R.

Findings

In 2011/12, the weight-adjusted coverage rate for receiving the hepatitis B birth dose was 48%, while the coverage with the hepatitis B antigen-containing combination vaccine was 55.1% based on both vaccination documents and recall; compared to 69.3% and 59.4% respectively in 2017. Ethno-linguistic group, maternal education, healthcare utilization and wealth were associated with receiving the vaccinations against hepatitis B.

Interpretation

National estimates of vaccination coverage rates can conceal country-specific regional or socio-economic variations. Children from Hmong-Mien households, from less wealthier households and whose mothers were less educated and were not able to or did not utilize healthcare were identified as being less likely to receive the vaccinations. These findings indicate the need for improving access to healthcare, in particular for minority groups.

Funding

This work was supported by the Ministry of Foreign and European Affairs, Luxembourg and the Luxembourg Institute of Health (project "Luxembourg-Laos Partnership for Research and Capacity Building in Infectious Disease Surveillance").

Modifiable risk factors for diphtheria: A systematic review and meta-analysis

Objective

To identify modifiable risk factors for diphtheria and assess their strengths of association with the disease.

Methods

This review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement. Electronic databases and grey literature were searched from inception until January 2023. Studies had to report on diphtheria cases and estimates of association for at least one potential risk factor or sufficient data to calculate these. The quality of non-ecological studies was assessed using the Newcastle-Ottawa Scale (NOS), while the quality of evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria.

Results

The search yielded 37,705 papers, of which 29 were ultimately included. All the non-ecological studies were of moderate to high quality. Meta-analysis of 20 studies identified three factors increasing the risk of diphtheria: incomplete vaccination (<3 doses) (pooled odds ratio (POR) = 2.2, 95% confidence interval (CI) = 1.4-3.4); contact with a person with skin lesions (POR = 4.8, 95% CI = 2.1-10.9); and low knowledge of diphtheria (POR = 2.4, 95% CI = 1.2-4.7). Contact with a case of diphtheria; sharing a bed or bedroom; sharing utensils, cups, and glasses; infrequent bathing; and low parental education were associated with diphtheria in multiple studies. Evidence for other factors was inconclusive. The quality of evidence was low or very low for all the risk factors.

Conclusions

Findings from the review suggest that countries seeking to control diphtheria need to strengthen surveillance, improve vaccination coverage, and increase people's knowledge of the disease. Future research should focus on understudied or inconclusive risk factors.

Genomic characterization of cocirculating Corynebacterium diphtheriae and non-diphtheritic Corynebacterium species among forcibly displaced Myanmar nationals, 2017-2019

Respiratory diphtheria is a serious infection caused by toxigenic Corynebacterium diphtheriae, and disease transmission mainly occurs through respiratory droplets. Between 2017 and 2019, a large diphtheria outbreak among forcibly displaced Myanmar nationals densely settled in Bangladesh was investigated. Here we utilized whole-genome sequencing (WGS) to characterize recovered isolates of C. diphtheriae and two co-circulating non-diphtheritic Corynebacterium (NDC) species - C. pseudodiphtheriticum and C. propinquum. C. diphtheriae isolates recovered from all 53 positive cases in this study were identified as toxigenic biovar mitis, exhibiting intermediate resistance to penicillin, and formed four phylogenetic clusters circulating among multiple refugee camps. Additional sequenced isolates collected from two patients showed co-colonization with non-toxigenic C. diphtheriae biovar gravis, one of which exhibited decreased susceptibility to the first-line antibiotics and harboured a novel 23-kb multidrug resistance plasmid. Results of phylogenetic reconstruction and virulence-related gene contents of the recovered NDC isolates indicated they were likely commensal organisms, though 80.4 %(45/56) were not susceptible to erythromycin, and most showed high minimum inhibition concentrations against azithromycin. These results demonstrate the high resolution with which WGS can aid molecular investigation of diphtheria outbreaks, through the quantification of bacterial genetic relatedness, as well as the detection of virulence factors and antibiotic resistance markers among case isolates.

The determinants of immunization coverage among children aged between 12 and 35 months: a nationwide cross-sectional study in Lao People's Democratic Republic

BACKGROUND

Immunization is one of the most important public health interventions for reducing morbidity and mortality in children. However, factors contributing to low immunization coverage are not fully understood in the Lao People's Democratic Republic (Lao PDR). Therefore, this study aimed to identify factors associated with full immunization coverage among children between 12 and 35 months, providing up-to-date information for immunization programs in Lao PDR.

METHODS

We analyzed the subpopulation of a nationwide cross-sectional survey using a multistage cluster sampling procedure to evaluate the measles and rubella seroepidemiology. In addition, we categorized children aged between 12 and 35 months into two groups: "fully immunized" children with a birth dose of Bacillus Calmette and Guérin vaccine, hepatitis B vaccine (Hep B), one and three doses for the measles-containing vaccine (MCV) and pentavalent vaccine and pneumococcal conjugate vaccine (PCV) and "partially immunized" children who missed any dose of vaccine. Immunization coverage was calculated as the ratio of "fully immunized" to the total. We compared the groups' demographic characteristics and health service utilization as independent variables. Multivariate logistic regression was used to assess the relationship between immunization coverage, various demographic factors, and health service utilization.

RESULTS

Overall, 256 of the 416 targeted pairs were included in the analysis. In total, 67.6% of the children were fully immunized. Childbirth at hospitals or health facilities (adjusted odds ratio: 9.75, 95% confidence interval: 5.72-16.62, p < 0.001) was the predictor of full immunization coverage. The 83 children in the partially immunized groups were attributed to Hep B at birth (46, 55.4%), three doses of PCV (34, 41.0%), and the first dose of the MCV (27, 32.5%).

CONCLUSION

Our study elucidated that the immunization status among children aged between 12 and 35 months in Lao PDR is satisfactory in improving access to healthcare by strengthening communication with residents regarding health service utilization, and expanding mobile outreach services may play a pivotal role in this endeavor. Further research is warranted to evaluate efforts to increase immunization coverage and target populations with limited access to healthcare.

Waning rate of immunity and duration of protective immunity against diphtheria toxoid as a function of age and number of doses: Systematic review and quantitative data analysis

Although the burden of diphtheria has declined greatly since the introduction of vaccines, sporadic outbreaks continue to be reported. WHO recommends booster doses after a primary series, but questions remain about the optimal interval between these doses. We conducted a systematic review and quantitative data analysis to quantify the duration of protective immunity after different numbers of doses. Fifteen cross-sectional seroprevalence studies provided data on geometric mean concentration (GMC). Single-year age-stratified GMCs were analyzed using a mixed-effect linear regression model with a random intercept incorporating the between-country variability. GMC was estimated to decline to 0.1 IU/ml in 2.5 years (95% CI: 0.9-4.0), 10.3 years (95% CI: 7.1-13.6), and 25.1 years (95% CI: 7.6-42.6) after receiving three, four and five doses, respectively. The results drawn from cross-sectional data collected in countries with different epidemiologies, vaccines, and schedules had several limitations. However, these analyses contribute to the discussion of optimal timing between booster doses of diphtheria toxoid-containing vaccine.

Susceptibility to Vaccine-Preventable Diseases in Four Districts of Xaysomboun Province, Lao People’s Democratic Republic

Xaysomboun province has some of the lowest health indicators in Lao People’s Democratic Republic (PDR). This cross-sectional study aimed to determine the vaccination, susceptibility and exposure status of the population to hepatitis B virus (HBV), measles, rubella, and tetanus. Participants aged 5 years and older were randomly selected from four districts. From each enrolled participant, demographic data and 5 mL of blood sample were taken. HBV surface antigen (HBsAg) and antibodies against HBV, measles, rubella, and tetanus were detected by ELISA. A total of 363 participants (age 5 to 80 years) were included. HBV exposure, as determined by anti-HBV core (anti-HBc) antibodies, was 56.2% overall, and was significantly higher among those aged ≥21 years (78.1%). HBsAg was detected in 9.4% overall and increased to 20% in ages 31–40 years. Only 13.8% of participants had serology indicative of vaccination (anti-HBs positive, anti-HBc negative). Seroprotection against measles was 74.6% overall but only 41.7% in children aged 5–10 years. Anti-rubella IgG was 94.2% overall and high in all age groups. Tetanus seroprevalence was only 47.4% overall but significantly higher in females aged 31–40 (75.6%). We suggest strengthening of routine and booster HBV, measles, and tetanus vaccine coverage in Xaysomboun province.

Investigation of a Large Diphtheria Outbreak and Cocirculation of Corynebacterium pseudodiphtheriticum Among Forcibly Displaced Myanmar Nationals, 2017-2019

BACKGROUND

Diphtheria, a life-threatening respiratory disease, is caused mainly by toxin-producing strains of Corynebacterium diphtheriae, while nontoxigenic corynebacteria (eg, Corynebacterium pseudodiphtheriticum) rarely causes diphtheria-like illness. Recently, global diphtheria outbreaks have resulted from breakdown of health care infrastructures, particularly in countries experiencing political conflict. This report summarizes a laboratory and epidemiological investigation of a diphtheria outbreak among forcibly displaced Myanmar nationals in Bangladesh.

METHODS

Specimens and clinical information were collected from patients presenting at diphtheria treatment centers. Swabs were tested for toxin gene (tox)-bearing C. diphtheriae by real-time polymerase chain reaction (RT-PCR) and culture. The isolation of another Corynebacterium species prompted further laboratory investigation.

RESULTS

Among 382 patients, 153 (40%) tested tox positive for C. diphtheriae by RT-PCR; 31 (20%) PCR-positive swabs were culture confirmed. RT-PCR revealed 78% (298/382) of patients tested positive for C. pseudodiphtheriticum. Of patients positive for only C. diphtheriae, 63% (17/27) had severe disease compared to 55% (69/126) positive for both Corynebacterium species, and 38% (66/172) for only C. pseudodiphtheriticum.

CONCLUSIONS

We report confirmation of a diphtheria outbreak and identification of a cocirculating Corynebacterium species. The high proportion of C. pseudodiphtheriticum codetection may explain why many suspected patients testing negative for C. diphtheriae presented with diphtheria-like symptoms.

Epidemiological, clinical, and public health response characteristics of a large outbreak of diphtheria among the Rohingya population in Cox's Bazar, Bangladesh, 2017 to 2019: A retrospective study

BACKGROUND

Unrest in Myanmar in August 2017 resulted in the movement of over 700,000 Rohingya refugees to overcrowded camps in Cox's Bazar, Bangladesh. A large outbreak of diphtheria subsequently began in this population.

METHODS AND FINDINGS

Data were collected during mass vaccination campaigns (MVCs), contact tracing activities, and from 9 Diphtheria Treatment Centers (DTCs) operated by national and international organizations. These data were used to describe the epidemiological and clinical features and the control measures to prevent transmission, during the first 2 years of the outbreak. Between November 10, 2017 and November 9, 2019, 7,064 cases were reported: 285 (4.0%) laboratory-confirmed, 3,610 (51.1%) probable, and 3,169 (44.9%) suspected cases. The crude attack rate was 51.5 cases per 10,000 person-years, and epidemic doubling time was 4.4 days (95% confidence interval [CI] 4.2-4.7) during the exponential growth phase. The median age was 10 years (range 0-85), and 3,126 (44.3%) were male. The typical symptoms were sore throat (93.5%), fever (86.0%), pseudomembrane (34.7%), and gross cervical lymphadenopathy (GCL; 30.6%). Diphtheria antitoxin (DAT) was administered to 1,062 (89.0%) out of 1,193 eligible patients, with adverse reactions following among 229 (21.6%). There were 45 deaths (case fatality ratio [CFR] 0.6%). Household contacts for 5,702 (80.7%) of 7,064 cases were successfully traced. A total of 41,452 contacts were identified, of whom 40,364 (97.4%) consented to begin chemoprophylaxis; adherence was 55.0% (N = 22,218) at 3-day follow-up. Unvaccinated household contacts were vaccinated with 3 doses (with 4-week interval), while a booster dose was administered if the primary vaccination schedule had been completed. The proportion of contacts vaccinated was 64.7% overall. Three MVC rounds were conducted, with administrative coverage varying between 88.5% and 110.4%. Pentavalent vaccine was administered to those aged 6 weeks to 6 years, while tetanus and diphtheria (Td) vaccine was administered to those aged 7 years and older. Lack of adequate diagnostic capacity to confirm cases was the main limitation, with a majority of cases unconfirmed and the proportion of true diphtheria cases unknown.

CONCLUSIONS

To our knowledge, this is the largest reported diphtheria outbreak in refugee settings. We observed that high population density, poor living conditions, and fast growth rate were associated with explosive expansion of the outbreak during the initial exponential growth phase. Three rounds of mass vaccinations targeting those aged 6 weeks to 14 years were associated with only modestly reduced transmission, and additional public health measures were necessary to end the outbreak. This outbreak has a long-lasting tail, with Rt oscillating at around 1 for an extended period. An adequate global DAT stockpile needs to be maintained. All populations must have access to health services and routine vaccination, and this access must be maintained during humanitarian crises.

Molecular and epidemiologic characterization of the diphtheria outbreak in Venezuela

In 2016, Venezuela faced a large diphtheria outbreak that extended until 2019. Nasopharyngeal or oropharyngeal samples were prospectively collected from 51 suspected cases and retrospective data from 348 clinical records was retrieved from 14 hospitals between November 2017 and November 2018. Confirmed pathogenic Corynebactrium isolates were biotyped. Multilocus Sequence Typing (MLST) was performed followed by next-generation-based core genome-MLST and minimum spanning trees were generated. Subjects between 10 and 19 years of age were mostly affected (n = 95; 27.3%). Case fatality rates (CFR) were higher in males (19.4%), as compared to females (15.8%). The highest CFR (31.1%) was observed among those under 5, followed by the 40 to 49 age-group (25.0%). Nine samples corresponded to C. diphtheriae and 1 to C. ulcerans. Two Sequencing Types (ST), ST174 and ST697 (the latter not previously described) were identified among the eight C. diphtheriae isolates from Carabobo state. Cg-MLST revealed only one cluster also from Carabobo. The Whole Genome Sequencing analysis revealed that the outbreak seemed to be caused by different strains with C. diphtheriae and C. ulcerans coexisting. The reemergence and length of this outbreak suggest vaccination coverage problems and an inadequate control strategy.

Diphtheria in Metro Manila, the Philippines 2006-2017: A Clinical, Molecular, and Spatial Characterization

BACKGROUND

Diphtheria is a vaccine-preventable disease that persists as a global health problem. An understanding of the pattern of disease is lacking in low- and middle-income countries such as the Philippines.

METHODS

We conducted a retrospective review of the clinical, microbiological, and epidemiological features of patients admitted with a clinical diagnosis of diphtheria to an infectious disease referral hospital in Metro Manila, the Philippines, between 2006 and 2017. Cases were mapped and the distribution was compared with population density. Corynebacterium diphtheriae isolates from between 2015 and 2017 were examined by multilocus sequence typing (MLST).

RESULTS

We studied 267 patients (range:12-54 cases/year) admitted between 2006 and 2017. The case fatality rate (CFR) was 43.8% (95% confidence interval, 37.8-50.0%). A higher number of cases and CFR was observed among children <10 years. Mortality was associated with a delayed admission to hospital and a lack of diphtheria antitoxin. Between 2015 and 2017 there were 42 laboratory-confirmed cases. We identified 6 multilocus sequence types (STs). ST-302 was the most common (17/34, 48.6%), followed by ST67 (7/34, 20%) and ST458 (5/34, 14%). Case mapping showed a wide distribution of diphtheria patients in Metro Manila. Higher case numbers were found in densely populated areas but with no apparent clustering of ST types.

CONCLUSIONS

Our analysis indicates that diphtheria remains endemic in Metro Manila and that the infection is frequently fatal in young children. Improved vaccine coverage and a sustainable supply of diphtheria antitoxin should be prioritized.

Diphtheria Antitoxin Administration, Outcomes, and Safety: Response to a Diphtheria Outbreak in Cox's Bazar Bangladesh

Background

Diphtheria has re-emerged over the past several years. There is a paucity of data on the administration and safety of diphtheria antitoxin (DAT), the standard treatment for diphtheria. The 2017–2018 outbreak among Rohingya refugees in Bangladesh was the largest in decades. We determined the outcomes of DAT-treated patients and describe the occurrence and risk factors associated with adverse reactions to DAT.

Methods

We conducted a retrospective study at the Médecins Sans Frontières Rubber Garden Diphtheria Treatment Center from December 2017–September 2018. Diphtheria was diagnosed based on the World Health Organization clinical case criteria. High-acuity patients were eligible for DAT. Safety precautions were meticulously maintained. We calculated the presence of adverse events by age, duration of illness, and DAT dosage using bivariate comparisons.

Results

We treated 709 patients with DAT; 98% (n = 696) recovered and were discharged. One-fourth (n = 170) had at least 1 adverse reaction. Common reactions included cough (n = 115, 16%), rash (n = 66, 9%), and itching (n = 37, 5%). Three percent (n = 18) had severe hypersensitivity reactions. Five patients died during their DAT infusion or soon afterwards, but no deaths were attributed to DAT.

Conclusions

Outcomes for DAT-treated patients were excellent; mortality was <1%. Adverse reactions occurred in one-quarter of all patients, but most reactions were mild and resolved quickly. DAT can be safely administered in a setting with basic critical care, provided there is continuous patient monitoring during the infusion, staff training on management of adverse effects, and attention to safety precautions.

Respiratory illness caused by Corynebacterium diphtheriae and C. ulcerans, and use of diphtheria anti-toxin in the United States, 1996-2018

Respiratory illness caused by Corynebacterium diphtheriae and C. ulcerans, and use of diphtheria anti-toxin in the United States, 1996-2018.

BACKGROUND

Respiratory diphtheria is a toxin-mediated disease caused by Corynebacterium diphtheriae. Diphtheria-like illness, clinically indistinguishable from diphtheria, is caused by C. ulcerans, a zoonotic bacterium that can also produce diphtheria toxin. In the United States, respiratory diphtheria is nationally notifiable: specimens from suspected cases are submitted to the Centers for Disease Control (CDC) for species and toxin confirmation, and diphtheria antitoxin (DAT) is obtained from CDC for treatment. We summarize the epidemiology of respiratory diphtheria and diphtheria-like illness and describe DAT use during 1996-2018 in the United States.

METHODS

We described respiratory diphtheria cases reported to the National Notifiable Diseases Surveillance System (NNDSS) and C. ulcerans-related diphtheria-like illness identified through specimen submissions to CDC during 1996-2018. We reviewed DAT requests from 1997-2018.

RESULTS

From 1996-2018, 14 respiratory diphtheria cases were reported to NNDSS. Among these 14 cases, 1 was toxigenic and 3 were non-toxigenic C. diphtheriae by culture and Elek, 6 were culture-negative but PCR-positive for diphtheria toxin gene, 1 was culture-positive without further testing, and the remaining 3 were either not tested or tested negative. Five cases of respiratory diphtheria-like illness caused by toxigenic C. ulcerans were identified. DAT was requested by healthcare providers for 151 suspected diphtheria cases between 1997-2018, with an average of 11 requests per year from 1997-2007, and 3 per year from 2008-2018.

CONCLUSIONS

Respiratory diphtheria remains rare in the United States, and requests for DAT have declined. Incidental identification of C. ulcerans-related diphtheria-like illness suggests surveillance of this condition might be warranted.

Seroprotection rate in adults after 1-dose, 2-dose, and 3-dose series of a reduced-diphtheria-tetanus toxoid vaccine (Td) during a diphtheria outbreak in Thailand

To evaluate seroprotection of different dosing strategies of reduced-diphtheria-tetanus-toxoid vaccine (Td) for adults during a diphtheria outbreak in Thailand, we enrolled 160 healthcare workers and 161 adults aged 20-60 years old and measured diphtheria antitoxin (DAT) level before administration of a Td vaccine. We scheduled a second Td at 4-8 weeks and a third Td at 6-12 months interval. DAT was measured 4 weeks after each dose. DAT levels of ≥0.1 and ≥1 IU/mL were considered as seroprotective and long-term seroprotective. Persons achieving long-term seroprotection were not given a further dose. The baseline seroprotection rate was 32.6%, which increased to 87.1% (95% confidence interval, 83.4-90.8%) after one dose. The seroprotection rate increased slightly with additional doses. The immune response was lowest among persons 30-49 years of age. We suggest 1-dose Td for adults during a diphtheria outbreak, and a 2-dose series being considered for those born before 1980.

Molecular epidemiology and antimicrobial susceptibility of outbreak-associated Corynebacterium diphtheriae in Thailand, 2012

Infections caused by Corynebacterium diphtheriae remain endemic in many countries. Since the implementation of the DTP (Diphtheria-Tetanus-Pertussis) vaccination program in 1977, only sporadic diphtheria cases have been reported in Thailand. In 2012, a diphtheria outbreak occurred in rural Thailand and 38 cases were reported, with the majority being adults (mean 22.1 years, range 5-72 years). The current study determined the genetic diversity of C. diphtheriae isolated from 83 individuals associated with either sporadic (n = 34) from 1994, 1996, 1997, 1998, 1999, 2000, 2012, and 2018, or 2012 outbreak (n = 49) diphtheria occurrences in Thailand. Antimicrobial susceptibility testing was performed on 41/83 isolates using broth microdilution. All sporadic (n = 27) and epidemic (n = 14) C. diphtheriae isolates (41/41; 100%) were susceptible to erythromycin (≤0.5 μg/ml), clindamycin (≤0.5 μg/ml), gentamicin (≤ 4 μg/ml), ciprofloxacin (≤1 μg/ml), and vancomycin (2 μg/ml), except tetracycline with a resistance rate of 34.1% (14/41 isolates). All isolates were intermediately resistant to penicillin (MIC range, 0.25-2 μg/ml). Multilocus sequence typing (MLST) revealed 17 sequence types (STs) among 83C. diphtheriae isolates. For the 2012 outbreak isolates, the predominant ST was ST243 (n = 34/49; 69.4%), followed by ST245 (n = 5/49; 10.2%) and ST244 (n = 4/49; 8.1%), whereas the main STs among the sporadic isolates were ST248 (n = 15/34; 44.1%), followed by ST209 (n = 7/34; 20.6%) and ST258 (n = 3/34; 8.8%). The ST243 outbreak strain was a single-locus variant of sporadic ST258. Phylogenetic analysis using concatenated sequences of 7 MLST genes from 17 STs revealed that ST243, ST248, and ST258 were located in the same cluster and ST243 appeared to have evolved from ST258, an endemic strain. This study highlights the importance of epidemiological surveillance together with characterization of C. diphtheriae strains to help inform the future control and prevention of diphtheria.

Cognitive function measured with the Revised Hasegawa's Dementia Scale among elderly individuals in Lao PDR

In Lao PDR, measurement of cognitive function has rarely been conducted among elderly individuals. This study aimed to investigate the cognitive function among elderly individuals who lived at their homes with family in Lao PDR. Participants were elderly individuals aged 60 years or over registered with the local government in urban (Vientiane capital; VC) and rural areas (Khammouane province; KP). Those with serious mental/physical diseases, those who could not walk by themselves, or those who could not speak the Lao language were excluded. The information was collected through interviews with the participants and their family members. A newly developed Lao version of the Revised Hasegawa’s Dementia Scale (HDS-R) was applied to measure cognitive function. The participants were 414 elderly individuals (224 males and 190 females) aged 60 to 98 years. The average HDS-R score was 23.0 among 115 men in VC, 22.7 among 92 women in VC, 20.3 among 109 men in KP, and 17.5 among 98 women in KP. The main caregiver was a daughter (40.6%) followed by a spouse (31.4%). Among 414 elderly individuals, 42 (10.0%) stated the necessity of support. Those with HDS-R < 20 accounted for 38.8% in men and 48.9% in women. The adjusted odds ratio of HDS-R < 20 was significant for those in rural areas (3.83) relative to those in urban areas. Among superficially healthy elderly individuals residing with their families, those with reduced cognitive function were more common among women and in rural areas.

Diphtheria outbreak in Yemen: the impact of conflict on a fragile health system

BACKGROUND

War in Yemen started three years ago, and continues unabated with a steadily rising number of direct and indirect victims thus leaving the majority of Yemen's population in dire need of humanitarian assistance. The conflict adversely affects basic socioeconomic and health conditions across the country.

METHODS

This study analyzed the recent ongoing diphtheria outbreak in Yemen and in particular, the health system's failure to ensure immunization coverage and respond to this outbreak. Data from the weekly bulletins of the national electronic Disease Early Warning System's (eDEWS) daily diphtheria reports and district immunization coverage were analyzed. The number of diphtheria cases and deaths, and immunization coverage (DPT) were reviewed by district including the degree to which a district was affected by conflict using a simple scoring system. A logistic regression and bivariate correlation were applied using the annual immunization coverage per district to determine if there was an association between diphtheria, immunization coverage and conflict.

RESULTS

The study results confirm the association between the increasing cases of diphtheria, immunization coverage and ongoing conflict. A total of 1294 probable cases of diphtheria were reported from 177 districts with an overall case fatality rate of 5.6%. Approximately 65% of the patients were children under 15 years, and 46% of the cases had never been vaccinated against diphtheria. The risk of an outbreak increased by 11-fold if the district was experiencing ongoing conflict p < 0.05. In the presence of conflict (whether past or ongoing), the risk of an outbreak decreased by 0.98 if immunization coverage was high p > 0.05.

CONCLUSION

The conflict is continuously devastating the health system in Yemen with serious consequences on morbidity and mortality. Therefore, the humanitarian response should focus on strengthening health services including routine immunization procedures to avoid further outbreaks of life-threatening infectious diseases, such as diphtheria.

Effects of geographic and economic heterogeneity on rotavirus diarrhea burden and vaccination impact and cost-effectiveness in the Lao People's Democratic Republic

Rotavirus enteritis is responsible for nearly 200,000 child deaths worldwide in 2015. Globally, many low- and middle-income countries have introduced rotavirus vaccine, resulting in documented reductions in hospitalizations and child mortality. We examined the potential impact and cost-effectiveness of introducing rotavirus vaccination in Lao People's Democratic Republic using an Excel-based spreadsheet model. We estimated mortality risk factors, patterns of care seeking, and vaccination access to predict outcomes for regional, provincial, and socioeconomic subpopulations for one birth cohort through their first five years of life and life course in Disability-Adjusted Life Years estimates. Socioeconomic status was defined by categorizing households into regional wealth quintiles based on a national asset index. We modeled a two-dose ROTARIX vaccine under current Gavi pricing and efficacy estimates from Bangladesh and Vietnam. DPT1 and DPT2 coverages were used to estimate rotavirus vaccination coverage. Probabilistic sensitivity analysis was used to assess the impact of uncertainty on model parameters on predicted incremental cost-effectiveness ratios (ICERs), including scenarios of increases in vaccination coverage. Rotavirus vaccination would prevent 143 child deaths/year, or 28% of annual rotavirus burden. The estimated national level ICER for rotavirus vaccination was $140/DALY, with regional socioeconomic subpopulation estimates ranging from $72/DALY for the poorest in the Central region to $353/DALY for the richest in the North region, indicating high cost-effectiveness. Within regions, ICERs are most favorable for children in the poorer and poorest quintiles. However, the full benefits of rotavirus vaccination will only be realized by reducing disparities in vaccination coverage, access to treatment, and environmental health. Improving vaccination coverage to equitable levels alone would prevent 87 additional child deaths per year.

Factors associated with routine immunization coverage of children under one year old in Lao People's Democratic Republic

BACKGROUND

Routine vaccination is administered free of charge to all children under one year old in Lao People's Democratic Republic (Lao PDR) and the national goal is to achieve at least 95% coverage with all vaccines included in the national immunization program by 2025. In this study, factors related to the immunization system and characteristics of provinces and districts in Lao PDR were examined to evaluate the association with routine immunization coverage.

METHODS

Coverage rates for Bacillus Calmette-Guerin (BCG), Diphtheria-Tetanus-Pertussis-Hepatitis B (DTP-HepB), DTP-HepB-Hib (Haemophilus influenzae type B), polio (OPV), and measles (MCV1) vaccines from 2002 to 2014 collected through regular reporting system, were used to identify the immunization coverage trends in Lao PDR. Correlation analysis was performed using immunization coverage, characteristics of provinces or districts (population, population density, and proportion of poor villages and high-risk villages), and factors related to immunization service (including the proportions of the following: villages served by health facility levels, vaccine session types, and presence of well-functioning cold chain equipment). To determine factors associated with low coverage, provinces were categorized based on 80% of DTP-HepB-Hib3 coverage (<80% = low group; ≥80% = high group).

RESULTS

Coverages of BCG, DTP-HepB3, OPV3 and MCV1 increased gradually from 2007 to 2014 (82.2-88.3% in 2014). However, BCG coverage showed the least improvement from 2002 to 2014. The coverage of each vaccine correlated with the coverage of the other vaccines and DTP-HepB-Hib dropout rate in provinces as well as districts. The provinces with low immunization coverage were correlated with higher proportions of poor villages.

CONCLUSIONS

Routine immunization coverage has been improving in the last 13 years, but the national goal is not yet reached in Lao PDR. The results of this study suggest that BCG coverage and poor villages should be targeted to improve nationwide coverage.

Characterization of serum anti-diphtheria antibody activity following administration of equine anti-toxin for suspected diphtheria

There is a global shortage of equine-derived diphtheria anti-toxin (DAT) for diphtheria treatment. There are few existing data on serum antibody concentrations and neutralizing activity post-treatment to support development of new therapeutics. Antibody concentrations were quantified by ELISA and anti-toxin neutralizing activity by cytotoxicity assay in serum from 4 patients receiving DAT for suspected diphtheria. Using linear mixed effects modeling, estimated mean (SE) half-life was 78.2 (20.0) hours. Maximum serum neutralizing activity ranged from 28.42–38.64 AU/mL with an estimated mean AUC_1–72 of 1396.7 (399.3) AU/mL*hr. These data provide a standard of comparison for development of novel anti-toxins to replace DAT.