Chia Yin Chong

KK Women's and Children's Hospital, Tumasik, Singapore

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Publications (12)26.54 Total impact

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    ABSTRACT: Haemophilus influenzae type b (Hib) conjugate vaccines have significantly limited Hib's disease impact in every country where it was introduced. We previously estimated invasive Hib disease incidence in Singapore at ∼4.4 per 100,000 children <5 years (from 1994 to 2003, period 1), but the vaccine was not included in the national childhood immunization schedule until May 2013 (although it was available privately). The current study aims to describe changes in Hib disease incidence and vaccine coverage prior to the introduction of the vaccine.
    Vaccine. 08/2014;
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    ABSTRACT: From 2011 to 2012, we received an unexpectedly high number of reports of suppurative lymphadenitis following administration of a BCG vaccine used in our childhood vaccination programme in Singapore. We sought to determine the local incidence rates of BCG-associated suppurative lymphadenitis across the 2009 to 2012 vaccinated cohorts, and to analyse the potential factors contributing to this outbreak.
    Vaccine. 08/2014;
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    ABSTRACT: Granulomatous cervicofacial lymphadenitis (GCL) is not uncommon in children. Nontuberculous mycobacteria (NTM) seem to be the predominant cause. We sought to study the clinical and microbiological profile of patients with GCL, and identify features that may impact outcome.
    Singapore medical journal 08/2014; 55(8):427-31. · 0.63 Impact Factor
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    ABSTRACT: In Singapore, reporting of adverse events following immunization (AEFI) was historically passive. In 2009, Health Sciences Authority collaborated with KK Women's and Children's Hospital to perform active surveillance for AEFI. We report the methodology and initial findings of this surveillance following childhood vaccines.
    Vaccine. 07/2014;
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    ABSTRACT: Introduction: Singapore had its first case of pandemic influenza A (H1N1) 2009 on 26 May 2009. As of 3 August 2009, 440 children with confirmed H1N1 were admitted to KK Women's and Children's Hospital (KKH). Materials and Methods: This is a retrospective case control study of children admitted from 26 May 2009 to 19 July 2009 with H1N1 infection. Cases and controls were first differentiated by whether they were complicated or non-complicated in nature, and subsequently analysed with regards to possible independent risk factors. Results: We analysed 143 admitted children; 48 cases and 95 controls (1 : 2 ratio). Significant comorbidity was found in 20.3% (n = 29) of patients with the majority having asthma (n = 18, 12.6 %) followed by obesity (n = 7, 4.9%). Binary logistic regression analysis showed risk factors for complicated disease were comorbidity (adjusted OR 6.0, 95% CI, 2.5 to 14.6, P < 0.0001) and age <2 years (adjusted OR 9.8, 95% CI, 2.4 to 40, P = 0.001). Age less than 5 years was not found to be a risk factor. Conclusion: In the early stages of an evolving influenza epidemic when oseltamivir stocks are low, oseltamivir treatment for influenza can be streamlined and offered to those at highest risk who are under 2 years old or have significant comorbidity to prevent complicated disease.
    Annals of the Academy of Medicine, Singapore 05/2013; 42(5):232-6. · 1.36 Impact Factor
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    ABSTRACT: BACKGROUND: Schools are important foci of influenza transmission and potential targets for surveillance and interventions. We compared several school-based influenza monitoring systems with clinic-based influenza-like illness (ILI) surveillance, and assessed the variation in illness rates between and within schools. METHODS: During the initial wave of pandemic H1N1 (pdmH1N1) infections from June to Sept 2009 in Singapore, we collected data on nation-wide laboratory confirmed cases (Sch-LCC) and daily temperature monitoring (Sch-DTM), and teacher-led febrile respiratory illness reporting in 6 sentinel schools (Sch-FRI). Comparisons were made against age-stratified clinic-based influenza-like illness (ILI) data from 23 primary care clinics (GP-ILI) and proportions of ILI testing positive for pdmH1N1 (Lab-ILI) by computing the fraction of cumulative incidence occurring by epidemiological week 30 (when GP-ILI incidence peaked); and cumulative incidence rates between school-based indicators and sero-epidemiological pdmH1N1 incidence (estimated from changes in prevalence of A/California/7/2009 H1N1 hemagglutination inhibition titers >=40 between pre-epidemic and post-epidemic sera). Variation in Sch-FRI rates in the 6 schools was also investigated through a Bayesian hierarchical model. RESULTS: By week 30, for primary and secondary school children respectively, 63% and 79% of incidence for Sch-LCC had occurred, compared with 50% and 52% for GP-ILI data, and 48% and 53% for Sch-FRI. There were 1,187 notified cases and 7,588 episodes in the Sch-LCC and Sch-DTM systems; given school enrollment of 485,723 children, this represented 0.24 cases and 1.6 episodes per 100 children respectively. Mean Sch-FRI rate was 28.8 per 100 children (95% CI: 27.7 to 29.9) in the 6 schools. We estimate from serology that 41.8% (95% CI: 30.2% to 55.9%) of primary and 43.2% (95% CI: 28.2% to 60.8%) of secondary school-aged children were infected. Sch-FRI rates were similar across the 6 schools (23 to 34 episodes per 100 children), but there was widespread variation by classrooms; in the hierarchical model, omitting age and school effects was inconsequential but neglecting classroom level effects led to highly significant reductions in goodness of fit. CONCLUSIONS: Epidemic curves from Sch-FRI were comparable to GP-ILI data, and Sch-FRI detected substantially more infections than Sch-LCC and Sch-DTM. Variability in classroom attack rates suggests localized class-room transmission.
    BMC Infectious Diseases 12/2012; 12(1):336. · 3.03 Impact Factor
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    ABSTRACT: In a previous study covering the period 1998-2004, we estimated the incidence of invasive pneumococcal disease (IPD) in Singapore to be 13.6 per 10(5) children aged <5 years, and determined that the 7-valent pneumococcal conjugate vaccine (PCV-7) would provide 78.1% serotype coverage for children aged <5 years. In the present study we sought to determine whether incidence and serotype trends have changed and to estimate pneumococcal vaccine coverage. We retrospectively reviewed IPD cases from 2005 to 2010 and calculated separate serotype proportions and population-based incidence rates for 2005-2007 (early PCV period) and 2008-2010 (late PCV period). PCV-7 coverage was obtained from the National Immunisation Registry, and patients with PCV-7 vaccine-type IPD (VT IPD) and non-vaccine-type IPD (non-VT IPD) were compared. One hundred and eighteen patients, with a mean age of 46 months, were identified during 2005-2010. The incidence rate of IPD increased to 14.8 (for 2005-2007) and 15.2 (for 2008-2010) per 10(5) children <5 years, despite a gradual increase in PCV-7 coverage to approximately 45% of the birth cohort receiving one or more doses of PCV-7. Although IPD due to serotypes 6B and 19A increased, there was a concomitant reduction in other serotypes. Coverage by PCV-7 progressively declined from 78.6% in 2005-2007 to 64.4% in 2008-2010 for children aged <5 years. Although population coverage with PCV-7 has risen, it remains suboptimal and the incidence of IPD remains unchanged. Furthermore, significant serotype changes (especially increases in 19A) have occurred. We need to adopt newer PCVs with broader serotype coverage and increase the number of children vaccinated as a matter of urgency.
    International journal of infectious diseases: IJID: official publication of the International Society for Infectious Diseases 03/2012; 16(3):e209-15. · 2.17 Impact Factor
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    ABSTRACT: Since the introduction of the pertussis vaccine into the standard immunization program, very few cases of pertussis have been detected. In 2007, it was felt that the number of cases being admitted for pertussis had increased and this was verified on a retrospective review done from 2004 to 2007 of children diagnosed with pertussis in KK Women's and Children's Hospital. To review the cases diagnosed with pertussis, the demographic profile and the outcome of these patients. A retrospective review was done of patients diagnosed with pertussis from 2004 to 2007. The patients were identified from records of the positive results obtained from the microbiology laboratory. In the preceding years, only 1-2 cases/year were reported with pertussis but this increased to 33 cases in 2007. 45 confirmed cases were analysed. Most infections were in infants below 6 months old (mean age 4.1 months) and almost all were not vaccinated. The average length of stay was 4.96 days (Range 2-14 days, SD 2.55). Children under 6 months had more severe disease in terms of ICU admissions (6% vs. 0%, p=0.70) and average length of stay (5.1 vs. 3.5 days, p=0.25) as compared to those above 6 months of age. Exposure to a symptomatic adult was documented in 64%, mainly parents (45%), older siblings (29%). Healthcare workers may also be a source of infection as one child had symptoms as early as the first week of life and none of the family members were coughing. There is a resurgence of pertussis in recent years with high morbidity in children who have not been vaccinated. A booster with Tdap vaccine should be considered for young adults and healthcare workers looking after children.
    Vaccine 01/2011; 29(13):2503-7. · 3.77 Impact Factor
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    Koh Cheng Thoon, Chia Yin Chong
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    ABSTRACT: Vaccination against the 2009 pandemic influenza A (H1N1) represents the best method of controlling spread, morbidity and mortality due to the pandemic. While this has been recommended for all healthcare-workers locally, it is unclear if they are willing to accept the vaccination. A cross-sectional survey was conducted before and after an educational talk on pandemic influenza and vaccines to ascertain responses and stated reasons, as well as identify associated factors. For 235 returned forms prior to the talk, 182 (77.4%) responded positively, while 161 of 192 (83.8%) who returned forms after the talk responded positively. Importantly, 12 of 47 (25.5%) initially negative responses turned positive after education. The desire to protect family, self and patients were the 3 most important reasons for staff wanting to receive the vaccine, while the concern regarding potential side effects was the most important reason for refusal. A high rate of willingness to receive pandemic influenza vaccine was found, which was in contrast to acceptance rates elsewhere and during previous influenza seasons. Education can play an important role in altering vaccine acceptance behaviour, with an emphasis on addressing concerns with regard to potential side effects.
    Annals of the Academy of Medicine, Singapore 04/2010; 39(4):307-6. · 1.36 Impact Factor
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    ABSTRACT: To understand the epidemiology of childhood bacterial diseases, including invasive pneumococcal disease, prospective surveillance was conducted among hospitalized children in Nha Trang, Vietnam. From April 2005 through August 2006, pediatricians at the Khanh Hoa General Hospital used standardized screening criteria to identify children aged <5 years who had signs and symptoms of invasive bacterial disease. All cerebrospinal fluid (CSF) and blood specimens collected were tested by bacterial culture. Selected culture-negative specimens were tested for Streptococcus pneumoniae by antigen detection or for Haemophilus influenzae, Moraxella catarrhalis, Neisseria meningitidis, and S. pneumoniae by polymerase chain reaction (PCR). A total of 987 children were enrolled (794 with pneumonia, 76 with meningitis, and 117 with other syndromes consistent with invasive bacterial disease); 84% of children were aged 0-23 months, and 57% were male. Seven (0.71%) of 987 blood cultures and 4 (15%) of 26 CSF cultures were positive for any bacterial pathogen (including 6 for H. influenzae type b and 1 for S. pneumoniae). Pneumococcal antigen testing and PCR identified an additional 16 children with invasive pneumococcal disease (12 by antigen testing and 4 by PCR). Among children aged <5 years who lived in Nha Trang, the incidence rate of invasive pneumococcal disease was at least 48.7 cases per 100,000 children (95% confidence interval, 27.9-85.1 cases per 100,000 children). S. pneumoniae and H. influenzae type b were the most common causes of laboratory-confirmed invasive bacterial disease in children. PCR and antigen testing increased the sensitivity of detection and provided a more accurate estimate of the burden of invasive bacterial disease in Vietnam.
    Clinical Infectious Diseases 03/2009; 48 Suppl 2:S57-64. · 9.37 Impact Factor
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    ABSTRACT: Influenza vaccine has been shown to be highly effective in temperate regions with well-defined seasonal influenza. Healthcare workers (HCWs) are advised to receive regular influenza vaccination to protect themselves and their patients. However, there are limited data on the efficacy of influenza vaccine in HCWs in the tropics. In this observational, investigator blinded cohort study, bi-monthly questionnaires recording influenza-like illness (ILI) episodes and medical leave were administered to 541 HCWs at the Singapore National University Hospital and KK Women's and Children's Hospital from 2004 to 2005. ILI was defined according to a standard symptom score. Baseline characteristics were comparable in both the vaccinated and non-vaccinated groups. Overall, the relative risk of self-reported ILI in vaccinated HCWs was 1.13 [95% confidence interval (CI), 0.98-1.13; P=0.107]; medical leave taken was lower in the vaccinated group [mean 0.26+/-0.6 days per visit, compared with 0.30+/-0.5 days in the non-vaccinated group (P=0.40)]. Because of the reported Northern Hemisphere 2003/04 vaccine mismatch, we stratified the cohort and determined that the group which received a matched vaccine had a relative risk of ILI of 0.49 (95% CI, 0.37-0.66; P<0.001), achieving a vaccine efficacy of 51%. Mean medical leave decreased significantly in HCWs who received the matched vaccine, compared with those who did not receive vaccination (0.13+/-0.3 vs 0.30+/-0.5; P<0.001) and with HCWs vaccinated with mismatched strains (0.13+/-0.3 vs 0.39+/-0.9; P=0.01). A well-matched influenza vaccine is effective in preventing ILI and reducing sickness absence in healthcare workers in tropical settings. Efforts need to be made to increase influenza vaccination rates and to improve the currently available vaccines.
    Annals of the Academy of Medicine, Singapore 06/2008; 37(6):465-9. · 1.36 Impact Factor
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    ABSTRACT: Invasive Haemophilus influenzae type b (Hib) diseases are major causes of childhood morbidity and mortality. For the period from 1994 to 2003, we retrospectively identified 53 children with invasive Hib disease including 31 with meningitis, 14 with pneumonia, 2 with septic arthritis, 2 with epiglottitis, 1 with neutropenic sepsis, and 3 who were bacteraemic without a focus. Two children died and 22 had serious sequelae; significantly, survivors with sequelae had presented with meningitis (P-value<0.001) or sepsis (P-value=0.001). During the 11-year period, the annual incidence of invasive Hib disease was estimated to be 4.4/100,000 children <5 years old. With rising affluence, decreasing costs of vaccines, and increased costs in caring for survivors, universal infant immunization with Hib vaccine may need to be reconsidered in Singapore.
    Vaccine 09/2007; 25(35):6482-9. · 3.49 Impact Factor