Pre-vaccination screening strategies for the use of the CYD-TDV dengue vaccine: A meeting report.

The first licensed dengue vaccine, CYD-TDV (Dengvaxia) is efficacious in seropositive individuals, but increases the risk for severe dengue in seronegative persons about two years after administration of the first dose. For countries considering the introduction of Dengvaxia, WHO recommends a pre-vaccination screening strategy whereby only persons with evidence of a past dengue infection would be vaccinated. Policy-makers need to consider the risk-benefit of vaccination strategies based on such screening tests, the optimal age to introduce the vaccine, communication and implementation strategies. To address these questions, the Global Dengue and Aedes-transmitted diseases Consortium (GDAC) organized a 3-day workshop in January 2019 with country representatives from Asia and Latin America. The meeting discussions highlighted many challenges in introducing Dengvaxia, in terms of screening test characteristics, costs of such tests combined with a 3-dose schedule, logistics, achieving high coverage rates, vaccine confidence and communication; more challenges than for any other vaccine introduction programme. A screening test would require a high specificity to minimize individual risk, and at the same time high sensitivity to maximize individual and population benefit. The underlying seroprevalence dependent positive predictive value is the best indicator for an acceptable safety profile of a pre-vaccination screening strategy. The working groups discussed many possible implementation strategies. Addressing the bottlenecks in school-based vaccine introduction for Dengvaxia will also benefit other vaccines such as HPV and booster doses for tetanus and pertussis. Levels of public trust are highly variable and context specific, and understanding of population perceptions and concerns is essential to tailor interventions, monitor and mitigate risks.

Optimizing national immunization program supply chain management in Thailand: an economic analysis.

OBJECTIVES: This study aimed to conduct an economic analysis of the transition of the conventional vaccine supply and logistics systems to the vendor managed inventory (VMI) system in Thailand. STUDY DESIGN: Cost analysis of health care program. METHODS: An ingredients based approach was used to design the survey and collect data for an economic analysis of the immunization supply and logistics systems covering procurement, storage and distribution of vaccines from the central level to the lowest level of vaccine administration facility. Costs were presented in 2010 US dollar. RESULTS: The total cost of the vaccination program including cost of vaccine procured and logistics under the conventional system was US$0.60 per packed volume procured (cm(3)) and US$1.35 per dose procured compared to US$0.66 per packed volume procured (cm(3)) and US$1.43 per dose procured under the VMI system. However, the findings revealed that the transition to the VMI system and outsourcing of the supply chain system reduced the cost of immunization program at US$6.6 million per year because of reduction of un-opened vaccine wastage. CONCLUSIONS: The findings demonstrated that the new supply chain system would result in efficiency improvement and potential savings to the immunization program compared to the conventional system.

Declining trend in the seroprevalence of infection with hepatitis A virus in Thailand.

Since the mid 1970s, infection with hepatitis A virus (HAV) in Thailand has shifted from hyper-endemic to mesoendemic. In 2004, to explore this trend in prevalence further, 3997 subjects from four geographically distinct provinces of Thailand were tested, in a commercial ELISA, for antibodies to HAV. The results indicate that the seroprevalence of HAV continues to fall, almost certainly because the profound socio-economic development that has occurred over the last few decades in Thailand has brought with it significant improvements in sanitation and personal hygiene. As exposure to HAV declines, however, the risks of symptomatic and potentially severe infection in adulthood (rather than asymptomatic infection during childhood) and of epidemics of such infection, which would lead to profound economic loss, increases. Improvements in hygiene and sanitation to reduce exposure to the virus and measures to reduce the incidence of symptomatic disease in those infected, such as vaccination (which may only be cost-effective when targeted at high-risk groups), need to be carefully considered.

Evaluation of growth monitoring and promotion (GMP) surveillance system Thailand 2002.

This study aims to describe the current practice on growth monitoring and promotion (GMP) system in Thailand, identify its constraints and recommend appropriate solutions. In the four provinces studied, 80 health centres were systematically selected. A total of 80 health officers, 183 health volunteers and 1,200 caretakers were interviewed and tested for GMP knowledge and practices. One-fourth of the health officers and half of the volunteers did not understand the objectives of the GMP. More than half of the health officers and volunteers did not have the skill to weigh properly. About half of the volunteers could not plot and explain the growth chart correctly. Only 40% of the caretakers understand the growth chart. Documentation of weight on child health card is lacking. We recommend adequate trainings and supervisions for health officers and volunteers, revised GMP guidelines to enhance integration with other programmes, and a study to identify the effectiveness of the GMP.

Diphtheria in Thailand in the 1990s.

Diphtheria remains endemic in developing countries, but there are limited published data on the subject. Thailand's diphtheria surveillance data are relatively complete and may give a fuller picture of the situation in similar countries. After routine immunization began in 1977, the incidence of reported diphtheria decreased by >98% to <0.1 case per 100,000 persons annually in the 1990s. Despite infant immunization coverage of >90%, diphtheria cases were reported throughout the 1990s, primarily among children <15 years old. Outbreaks were linked to both persistent endemic circulation and to importation of toxigenic Corynebacterium diphtheriae; suboptimal immunization coverage in minority and disadvantaged groups contributed. A serologic survey found 25% of adults 20-39 years old and 14% of adolescents 10-19 years old lacked immunity to diphtheria; these data indicate an accumulation of susceptible adolescents and adults. Diphtheria remains a threat in Thailand; improvements in diphtheria control will depend on improving childhood immunization coverage in Thailand and the surrounding region.

An outbreak of Influenza A virus in a hilltribe village of Mae Hong Son Province Thailand, 1997.

An outbreak of Influenza A virus occurred in a hilltribe village between July 18th and August 8th, 1997. The overall infection rate was 92.5 per cent. The household infection rate was higher in the crowded part of the village. The symptoms analyzed after all, were fever (100%), cough (99%), headache, myalgia (78.1%) and rhinorrhea (50.5%). The patients were self - recovery within 5-7 days. Isolation and Haemagglutination inhibition test (HI) were undertaken to identify the causative agent. The results were positive for influenza A/Wuhan/359/95(H3N2) - like strain. The outbreak did not spread to the town, possibly because of the differences in environmental condition. Predisposing factors of the village that may have influenced the outbreak were crowded living quarters, cold (8 - 10 degrees C) and moist weather, poor personal hygiene and improper sanitation.

Food poisoning outbreak from contaminated fish-balls.

On February 9th, 1998, a food poisoning outbreak occurred at a boarding school for underprivileged students. An unmatched case-control study was done. An environmental survey, laboratory study of rectal swab culture, fish-balls, water and the cooking utensils were also performed. There were 132 suspect cases, of which the attack rate in teachers was 9.8 per cent (4/41), 16.7 per cent (1/6) in the food handlers and 15.7 per cent (127/810) in the students. The median incubation period was 18 hours. Analysis of food consumption revealed those who ate lunch noodles had the highest risk (OR 3.8, 95% CI 0.6-5.9). In details of food components, those who ate fish-balls in curry had the only significant risk (OR 3.5, 95% CI 1.2-0.8) of becoming ill when compared to those who did not. Fish-balls in noodles and curry had a dose response relationship. Bacterial culture from 25 grams of fish-balls was positive for Vibrio parahaemolyticus. The fish-balls in noodles and curry were identified as the implicated food. The modes of contamination were uncooked food, cooking utensils and the food handlers. The manufacturer, which had no license to operate and had poor standards of sanitation, was closed by the Food and Drug Administration.

Screening assessment of persons 40-59 years of age in rural Thailand by a mobile health unit.

This paper reports a screening survey using a mobile unit to determine the prevalence of chronic disorders among persons aged 40-59 years in rural Thailand. A total of 4,812 persons from all the 54 rural villages in Mae Sot District, Tak Province, northern Thailand, were interviewed and examined in 1995. A higher proportion (59.3%) of men were current tobacco smokers than among women (40.4%). A higher proportion (69.6%) of men were current alcohol drinkers compared with women (38.6%). Cutting/piercing was the most frequently reported injury, followed by falls. About half (47.9%) of the persons surveyed had a body mass index (BMI) between 20 and 24.9 and only 2.6 per cent had a BMI of 30 or over. The overall prevalence rates of hypertension and diabetes in the persons surveyed were 13.3 per cent and 2.4 per cent respectively. Of the persons screened, 28.8 per cent had borderline-high blood cholesterol (200-239 mg/dl) and 12.9 per cent had high blood cholesterol (> or = 240 mg/dl). About 61 per cent of hypertensive persons, 92 per cent of diabetic persons, and nearly all of those with dyslipidaemia were first detected during this screening programme. Five women with breast cancer and 22 with benign breast disorders were also identified during the survey. A screening programme using a mobile unit may be useful in identifying treatable disorders in rural areas, where existing screening services cannot effectively cover the population at risk.

Recurrence of yaws outbreak in Thailand, 1990.

In November 1990, an outbreak of yaws was reported in a rural village of southern Thailand. A survey consisting of history taking, physical examination and blood tests for VDRL and TPHA was undertaken in the whole village and in the primary school of the village. A yaws case was defined as a person who had a positive VDRL confirmed by TPHA without history of other treponemal infection or post-treatment of yaws. Fifty-four cases, an attack rate of 23%, were found in the age range from 2 to 79 years old. The epidemic curve started with a few cases in 1989 and early 1990 with an increasing number of cases from June, and reached its peak in November. Half of the cases (53.7%) were children under 15 years. Male cases were higher than female (1.5:1). A survey of 105 primary school students found an attack rate of 32% (34/105) and the prevalence was higher in younger classes. Benzathine penicillin injection was given to cases for treatment. From this investigation, the Ministry of Public Health was alerted about the recurrence of yaws. Strengthening health education and surveillance activities was recommended in adjacent districts and provinces. The extent of the problem was assessed through surveys among school children and expanded to their family members if cases of yaws were found.