Abstract
BackgroundIn Ho Chi Minh City, Vietnam, more than one-third of admissions to the two paediatric hospitals are attributable to four infectious syndromes: dengue, diarrhoeal disease, acute respiratory infection, and hand, foot and mouth disease. We have established a large prospective birth cohort study to investigate individual, environmental, virological, and immunological determinants of infection and disease in infants. Specific research questions are focused on the role of maternal antibody in protection against infection in infancy, and the adaptive immune response to vaccination and natural infection. This paper presents the cohort design, methods, and baseline characteristics of the participants enrolled in the first two years.Methods/designWomen are enrolled prior to delivery at one hospital in each of two catchment areas: an urban district in central HCMC, and a mixed urban/rural district in the Mekong Delta 150 km southwest of HCMC. Infants are enrolled within 3 days of birth, and maternal and cord blood samples are collected. Routine blood samples and data on growth, health status and vaccinations are collected from infants at scheduled visits at 4, 9 and 12 months. Clinical data and specimens are collected from infants presenting at a study clinic, or admitted to hospital, with any of the the four infectious syndromes of interest.DiscussionIn four years since since the study began in July 2009, >6400 infants have been enrolled, and enrolment is ongoing. Attrition is low: 84% of participants have completed the full 12-month follow-up period. Baseline characteristics of the first 4300 enrollees are presented here. We have demonstrated the feasibility of establishing a large prospective study of infectious diseases in infancy in a resource-limited setting, with minimal loss to follow-up. Our linked socio-demographic, clinical and laboratory data will help elucidate the viral aetiology and epidemiology of common infectious diseases of infancy, and can inform the implemention of existing and future vaccines. This study furthermore provides a platform to which additional endpoints could be added in the future.
Highlights
In Ho Chi Minh City, Vietnam, more than one-third of admissions to the two paediatric hospitals are attributable to four infectious syndromes: dengue, diarrhoeal disease, acute respiratory infection, and hand, foot and mouth disease
We have demonstrated the feasibility of establishing a large prospective study of infectious diseases in infancy in a resource-limited setting, with minimal loss to follow-up
In southern Vietnam, more than one-third of admissions to the two referral paediatric hospitals in Ho Chi Minh City (HCMC) are attributable to 4 infectious diseases and syndromes: dengue, diarrhoeal disease, acute respiratory infection (ARI), and hand, foot and mouth disease (HFMD), with an average of 147,000 patients admitted with these syndromes annually to these two hospitals alone
Summary
Characteristics of the cohort population Between 1 July 2009 and 31 August 2011, 4318 infants born to 4301 women were enrolled in the birth cohort study. Acute illness episodes does have the potential to introduce bias into any analyses that compare clinical endpoints between subgroups, where those subgroups are likely to differ systematically in their completeness of case ascertainment – for example, between study sites or socioeconomic groups or infants with different baseline health status This limitation will be considered when interpreting any subgroup-specific estimates of disease incidence. Study limitations Our cohort was not designed as a population-representative sample; for pragmatic reasons, we restricted our catchment areas to one urban and one mixed urban/rural district where we had existing research collaborations, and where the burden of dengue and other infectious diseases is known to be high This may limit the generalisability of the epidemiological findings, but is unlikely to affect the external validity of the immunological and virological analyses which are the focus of our primary research questions. Authors’ information Additional members of the Birth Cohort Study team who contributed to the design and implementation of the study are as follows: Nguyen Thanh Tien, Nguyen Thi Hong Van, Bridget Wills, Jeremy Farrar (Oxford University Clinical Research Unit); Nguyen Van Truong (Hung Vuong Hospital); Mai Ngoc Lanh, Pham Thi Hong Phuong, Vo Thi Bich Ngoc, Dang Thi Ngoc Ha, Le Thi Phuong (Dong Thap Hospital); Nguyen Thi Thanh Thuy (District 8 Hospital); Nguyen Thanh Hung, Nguyen Minh Tuan (Children’s Hospital No 1 HCMC)
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