COVID-19 vaccination for children in Malaysia - A position statement by the College of Paediatrics, Academy of Medicine of Malaysia.

The availability of COVID-19 vaccines and mass vaccination programmes in adults have significantly reduced the case attack rates and disease burden. COVID-19 vaccination successfully decreases the population at risk of infection, allowing for the safer re-opening of economies and reducing the pandemic's crippling impact on healthcare systems. However, the rapidly mutating severe acute respiratory syndrome-coronavirus-2 poses challenges in diminishing vaccine-induced immunity and vaccinating a significant proportion of adults to achieve herd immunity. These challenges necessitated adolescent vaccination. With the recent emergence of the highly transmissible Omicron variant and the increasing COVID-19 hospitalisation rates of children below 12 years old, many countries opted to also vaccinate younger children. Phase II/III clinical trials and real-world experience demonstrate that COVID-19 vaccinations are effective and safe for younger children and adolescents. Before Malaysia introduced its national COVID-19 vaccination programme for children 5-11 years old (which ran between March and June 2022), an expert advisory statement was issued by the College of Paediatrics, Academy of Medicine of Malaysia, to highlight the benefits and importance of vaccinating children. The advisory statement included clarifications about vaccine-related side effects such as post-vaccination myocarditis and allergic reactions to encourage informed decision making by healthcare providers and parents. This paper, which was prepared based on the critical appraisal of the current evidence, evaluation of the international experiences and the positive impact of COVID-19 vaccination in children, collectively sums up the rationale to support and ensure the success of the nationwide vaccination programme for children. Hence, the College recommends COVID-19 vaccination for children in Malaysia.

Observations of boundary layer wind and turbulence of a landfalling tropical cyclone.

This study investigates the atmospheric boundary layer structure based on multiple-level tower observations with a height of 350 m during the landfall of Super Typhoon Mangkhut (2018). Results show a layer of log wind profile outside of the radius of maximum wind speed with a height of 100 m or larger. The log layer height increases with the wind speed. The height of the constant flux layer reaches ~ 300 m for 10-m wind speeds less than 13 m s-1 while this height decreases with the wind speed. Momentum fluxes and turbulent kinetic energy increase with the wind speed at all vertical levels. The drag coefficient and surface roughness length estimated at the tower location have values of 7.3 × 10-3 and 0.09 m, respectively, which are independent of wind speed. The estimated vertical eddy diffusivity and mixing length increase with height up to ~ 160 m and then slowly decrease with height. The vertical eddy diffusivity increases with the wind speed while the vertical mixing length has no dependence on the wind speed. Comparing our results with previous work indicates that the vertical eddy diffusivity is larger over land than over ocean at a given wind speed range.

Spread of SARS-CoV-2 aerosols via two connected drainage stacks in a high-rise housing outbreak of COVID-19.

Vertical transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) along a vertical column of flats has been documented in several outbreaks of coronavirus disease 2019 (COVID-19) in Guangdong and Hong Kong. We describe an outbreak in Luk Chuen House, involving two vertical columns of flats associated with an unusually connected two-stack drainage system, in which nine individuals from seven households were infected. The index case resided in Flat 812 (8th floor, Unit 12), two flats (813, 817) on its opposite side reported one case each (i.e., a horizontal sub-cluster). All other flats with infected residents were vertically associated, forming a vertical sub-cluster. We injected tracer gas (SF6) into drainage stacks via toilet or balcony of Flat 812, monitored gas concentrations in roof vent, toilet, façade, and living room in four of the seven flats with infected residents and four flats with no infected residents. The measured gas concentration distributions agreed with the observed distribution of affected flats. Aerosols leaking into drainage stacks may generate the vertical sub-cluster, whereas airflow across the corridor probably caused the horizontal sub-cluster. Sequencing and phylogenetic analyses also revealed a common point-source. The findings provided additional evidence of probable roles of drainage systems in SARS-CoV-2 transmission.

Path integration (PI) method for the parameter-retrieval of aircraft wake vortex by Lidar.

Aircraft wake is a pair of strong counter-rotating vortices generated behind a flying aircraft. It might be very hazardous to a following aircraft and the real-time detection of it is of great interest in aviation safety field. Vortex-core positions and velocity circulations, which respectively represent the location and strength of a wake, are two characteristic parameters that have attracted the main attention in wake vortex detection. This paper introduces a new algorithm, the Path Integration (PI) method, to retrieve the characteristic parameters of wake vortex. The method uses Doppler velocity distribution to locate the vortex-core positions, and the integration of Doppler velocity along a LOS (line-of-sight) is derived as a linear expression about the circulations. From this expression, the circulations can be solved with the least square method. Moreover, an vortex-core position adjusting method is proposed to compensate the compressing and expanding effects of wake vortex caused by the scanning of Lidar beam. Basically, the use of Doppler velocity integration can improve the method's adaptability in turbulence environment and mitigate the impact of noise. Numerical examples and field detection data from Hong Kong international airport and Tsingtao Liuting airport have well verified the good performance of the method, in terms of both accuracy and efficiency.

Safety and efficacy of tirofiban combined with endovascular treatment in acute ischaemic stroke.

BACKGROUND AND PURPOSE: Tirofiban is used off-label in clinical practice for acute ischaemic stroke (AIS). However, it is unknown whether tirofiban increases the bleeding risk or improves the outcome of endovascular treatment (EVT) in AIS. This study evaluated the efficacy and safety of tirofiban in combination with EVT for AIS. METHODS: Consecutive patients with AIS receiving EVT were included in the prospective stroke registry from 2015 to 2018. The efficacy outcomes were modified Rankin Scale (mRS) score at 3 months and National Institutes of Health Stroke Scale (NIHSS) score at 24 h. The safety outcomes were symptomatic intracerebral hemorrhage (sICH), any in-hospital intracerebral hemorrhage, in-hospital death and 3-month death. RESULTS: Of 211 patients, 82 (38.9%) received tirofiban. A total of 39 (48.1%) with tirofiban and 44 (36.1%) without tirofiban had mRS score 0-2 [adjusted odds ratio (OR), 2.41; 95% confidence interval (CI), 1.11-5.23, P = 0.026]. NIHSS score at 24 h was lower in the tirofiban group (9.5 vs. 12.0, adjusted P = 0.032). Five (6.1%) patients with tirofiban and 16 (12.4%) without tirofiban had sICH (adjusted OR, 0.54; 95% CI, 0.16-1.83, P = 0.32). In-hospital intracerebral hemorrhage occurred in 10 (12.2%) patients with tirofiban and 41 (31.8%) without tirofiban (adjusted OR, 0.32; 95% CI, 0.13-0.76, P = 0.01). In-hospital death occurred in 7 (8.5%) patients with tirofiban and 16 (12.4%) without tirofiban (adjusted OR, 0.69; 95% CI, 0.22-2.13, P = 0.52). A total of 13 (15.9%) patients with tirofiban and 22 (17.1%) without tirofiban were dead at 3 months (adjusted OR, 0.98; 95% CI, 0.40-2.40, P = 0.96). CONCLUSIONS: Tirofiban in combination with EVT was associated with a lower mRS score at 3 months and NIHSS score at 24 h. It was not associated with a higher rate of sICH, in-hospital death and death at 3 months.

Parameter-retrieval of dry-air wake vortices with a scanning Doppler Lidar.

A wake vortex is a form of irregular airflow generated by a flying aircraft, which can cause a severe hazard for aviation. To quantify the hazard of a wake after fully roll-up and before rebound, this paper proposes an algorithm to retrieve its characteristic parameters (circulations, vortex-core positions, and vortex-core radii) with a scanning Doppler Lidar. In the algorithm, a governing equation related to the Doppler velocities and characteristic parameters is established based on the aerosols' weak inertia, from which the target parameters are solved with an optimization method. During the process, the distortion of Doppler velocity caused by the scanning of the Lidar beam is adjusted by the Doppler acceleration to achieve better estimations of the target characteristic parameters. Good performance of the algorithm has been verified by simulation and field detection data.

New inflow boundary conditions for modeling twisted wind profiles in CFD simulation for evaluating the pedestrian-level wind field near an isolated building.

The hilly topography of Hong Kong influences oncoming winds and gradually changes their wind directions along the profiles' height. The vertical variation in wind directions, or the twist effect, significantly influences the Pedestrian Level Wind (PLW) field in urban areas of Hong Kong, thus it is a topic demanding systematic investigations. In this study, a new set of inflow boundary conditions are proposed to model twisted wind flows in Computational Fluid Dynamic (CFD) simulations. The new inflow boundary condition derived based on the horizontal homogeneous assumption, specifies a vertical profile of lateral wind speeds at the inlet boundary to sustain the twist effect in the empty computational domain. The proposed boundary conditions are used to simulate the PLW fields near three isolated buildings with different Height-to-Width ratio using two CFD codes; OpenFOAM, and FLUENT. The results reveal that OpenFOAM is more reliable in simulating PLW fields in twisted wind flows using the new set of boundary conditions. The three-dimensional flow field provided by the OpenFOAM simulation shows sparse streamlines downstream the buildings, indicating lack of organized eddies in the building far wake, which negatively affects the dispersion of air pollutants in twisted winds.

An analysis of aerosol liquid water content and related impact factors in Pearl River Delta.

Aerosol liquid water content (ALWC) has an important effect on atmospheric visibility as well as heterogeneous chemical reactions. In this paper, we used the data size-resolved particle hygroscopic growth factor, and particle number size distribution (PNSD) obtained from H-TDMA and SMPS to compute ALWC at the Guangzhou Panyu site from the winter of 2014 and the spring of 2015. The corresponding results were relatively consistent with the trend for ALWCISO calculated from the ISORROPIA II thermodynamic equilibrium model based on the measurement of aerosol water-soluble ionic compositions obtained from MARGA, with a linear fit yielding an R2 value of 0.76. The fact that ALWCHTDMA was somewhat higher than ALWCISO at low RH values was at least partially attributable to the fact that effects resulting from organic matter hygroscopicity were not taken into account when computing ALWCISO. In sensitivity testing, ambient relative humidity, PNSD and particle hygroscopicity were all found to affect ALWC, in that order. Particles of different modes made different contributions to ALWC with the contributions of nuclear, Aitken, accumulation and coarse modes assessed at <1%, 3%, 85% and 12%, respectively, indicating that the contribution of accumulation mode particles to ALWC dominated among all the aerosol particle modes. During clean processes, decreases in relative humidity and PM2.5 both resulted in a decrease in ALWC. During the pollution processes, calm winds caused local particle accumulation, with ALWC increasing as RH increased. Intraday trends in ALWC and relative humidity were consistent, with minimum mean values observed in the afternoon due to low ambient relative humidity inhibiting an increase in ALWC. However, diurnal variation of aerosol hygroscopicity and ALWC tended to be somewhat anti-correlated, indicating that diurnal changes in aerosol hygroscopicity are not a primary factor resulting in ambient AWLC changes.

Impact of relative humidity on visibility degradation during a haze event: A case study.

Light scattering of aerosols depends on ambient relative humidity (RH) since hygroscopic particles absorb significant water at high RH, and this results in low visibility. This paper used custom-made parallel nephelometers (PNEPs) to measure aerosol light scattering enhancement factor ƒ(RH), and utilized data including visibility, PM2.5, black carbon, water-soluble ions mass concentrations and surface meteorological parameters, in conjunction with background weather conditions, to analyze a haze event in Guangzhou during 8th-15th Dec. 2013. Unfavorable weather conditions, such as high RH and low wind speed, were observed during the haze event. The hourly average mass concentration of PM2.5 was 127µg/m(3), with concentration of 192.4µg/m(3) on 9th and 196µg/m(3) on 13th. The ƒ(RH) did not exhibit significant changes during this haze process, with value of ƒ(80%)=1.58±0.07. Although the mass fraction of water-soluble ions to PM2.5 decreased after 12th Dec., the aerosol hygroscopicity might not have changed significantly since the mass fraction of nitrate became more dominant, which has stronger ability to take up water. The best-fitted parameterized function for ƒ(RH) is ƒ(RH)=0.731+0.1375∗(1-RH/100)(-1)+0.00719∗(1-RH/100)(-2). Combining the fixed parameterization of ƒ(RH) above, the visibility was calculated with the measured light scattering and absorption coefficient of particles and gas under dry condition, as well as ambient RH. The predicted visibility range agrees well with the measurements without precipitation. Using ISORROPIA II model, the calculated aerosol liquid water content (ALWC) at ambient RH varied consistently with the PM2.5 under lower RH, while it was more influenced by high RH. This work also show that high RH accompanied with precipitation will enhance aerosol hygroscopic growth effect, leading to further visibility degradation, even if PM2.5 mass decreased due to precipitation.

Cystic fibrosis in Malaysian children.

Cystic fibrosis (CF) is an autosomal recessive disease commonly found among the Caucasian population. The availability of sweat test and with increasing experience have made it possible to diagnose more cases of CF. Our first case of CF was diagnosed 16 years ago and to date we have managed sixteen cases of CF. Sixteen children were diagnosed with CF in our units at the Paediatric Institute and University Malaya Medical Centre (UMMC). They were referred with either one or all of the following symptoms: i) recurrent pneumonia, ii) bronchiectasis, iii) failure to thrive, iii) malabsorption or iv) history of meconium ileus obstruction during the neonatal period. When the clinical features suggested strongly of CF, sweat tests will be performed in duplicates and considered positive when the sweat chloride or sweat sodium was more than 60 mmol/l for both results. Seventy- two hours fecal fat excretion or stool for fat globule was performed to document malabsorption. From the year 1987 to 2003, 16 patients were confirmed to have cystic fibrosis in Malaysia by positive sweat tests. Thirteen patients were diagnosed in Paediatric Institute while the remaining three were diagnosed in UMMC. On follow-up two patients died due to severe bronchopneumonia at the age of two years old. Although once considered rare, CF should now be considered in any children with clinical presentations of recurrent chest infections, bronchiectasis, in the presence or absence of malabsoption stmptoms and in neonates with meconium ileus obstruction.

Cost of hospitalization for respiratory syncytial virus chest infection and implications for passive immunization strategies in a developing nation.

UNLABELLED: Respiratory syncytial virus (RSV) chest infection is a common cause of hospitalization in the very young child. The aim of this study was to determine the direct cost of resource utilization in the treatment of children hospitalized with RSV chest infection and the potential cost-savings with passive immunization for high-risk infants. An audit of the hospital resource consumption and its costs was performed for 216 children aged < 24 mo admitted with RSV chest infection between 1995 and 1997. The cost-saving potential of passive immunization using monoclonal RSV antibodies during the RSV season was determined by assuming an 0.55 efficacy in hospitalization reduction when administered to "high-risk" infants according to the guidelines outlined by the American Academy of Pediatrics (AAP). The hospital treatment cost of 1064 bed-days amounted to USD 64 277.70. Each child occupied a median of 4.0 bed-days at a median cost of USD 169.99 (IQ1 128.08, IQ3 248.47). Children, who were ex-premature or with an underlying illness were more likely to have a longer hospital stay, higher treatment costs and need for intensive care. Ten (42%) of 24 ex-premature infants fulfilled the recommended criteria for passive immunization. Its use resulted in an incremental cost of USD 31.39 to a potential cost saving of USD 0.91 per infant for each hospital day saved. CONCLUSION: Ex-prematurity and the presence of an underlying illness results in escalation of the direct treatment cost of RSV chest infection. Current guidelines for use of passive RSV immunization do not appear to be cost-effective if adopted for Malaysian infants.

Prescribing patterns for childhood asthma treatment in general practice.

The treatment preferences of 109 general practitioners (GPs) for childhood asthma were determined. Availability and adherence to clinical practice guidelines (CPG) for the treatment of childhood asthma was also assessed. Ninety eight (90%), 60 (55%) and 33 (30%) GPs considered nocturnal symptoms > 2 times/week, exercise induced wheeze and cough respectively as indications for preventer therapy. An oral preparation was preferred for relief medication [72 (66%) for 2-5 years, 60 (55%) for > 5 years]. An inhaled preparation was however preferred for preventer medication [60 (55%) for 2-5 years, 85 (78%) for > 5 years]. The oral form was more likely prescribed for asthmatic children 2-5 years (p < 0.001). Corticosteroids and ketotifen were the commonest inhaled and oral preventer treatment prescribed respectively. Only 36(33%) GPs have a CPG copy for reference. Children with asthma symptoms that require preventer therapy may not always be identified in general practice. The oral route remains important for asthma medication especially in young children. The accessibility to the CPG among GPs is disappointing.

Open lung biopsy for diffuse parenchymal lung disease in children.

An open lung biopsy was performed in 12 children with diffuse parenchymal lung disease. A definitive histopathological diagnosis was obtained from all procedures but determined treatment options in only 10 children (83%). Three (25%) children were ventilated for respiratory failure prior to the procedure. Four (44%) of the other 9 children required ventilatory support after the procedure. Three (25%) children developed post-op pneumothorax that resolved fully with chest tube drainage. There were no deaths as a direct result of the procedure. Open lung biopsy is useful in providing a definitive diagnosis in children with diffuse parenchymal lung disease and determining treatment in the majority of cases. The procedure was well-tolerated with minimal complications.

Risk factors associated with severe viral croup in hospitalised Malaysian children.

OBJECTIVE: To determine the risk factors associated with severe viral croup in hospitalised Malaysian children. METHODOLOGY: The medical records of children aged less than five years admitted with a diagnosis of viral croup between 1994 and 1999 were reviewed. Severe viral croup was diagnosed in children who had stridor at rest with marked recession associated with central cyanosis or altered level of consciousness. Multivariate logistic regression analysis was performed to identify risk factors associated with severe viral croup. RESULTS: Eighteen (14.7%) of 122 children with viral croup were severe. These children were older (mean age 16.8 +/- 7.2 vs 12.6 +/- 6.6 months, p = 0.01) and had a shorter duration of illness prior to admission (1.7 +/- 0.7 days vs 2.3 +/- 1.4 days, p = 0.03). Age between 12 and 24 months (OR 3.8 95% Cl 1.3, 12.7, p = 0.02) and fever (OR 5.7 95% Cl 2.9, 15.6, p = 0.02) were the only risk factors associated with severe viral croup after multivariate logistic regression analysis. Only three children or 2.5 per 100 children admitted with viral croup required ventilation. CONCLUSION: Only a small number of children admitted particularly those between 12 to 24 months with fever developed severe viral croup. Recognition of these risk factors provides a guide in selecting children who will most likely benefit from steroid therapy. The overall outcome was nonetheless favourable.

Do paediatric research presentations at local meetings get published?

Accessibility of research done locally to clinicians remains limited unless it is in the published form. The publication rate of research presentations at the Annual Malaysian Paediatric Association, Perinatal Society of Malaysia and Academy of Medicine Malaysia in 1997 and 1998 was determined. One hundred and five (95.5%) of 110 research presentations were carried out in Malaysia. Thirty-seven (35.2%) presentations were published. University-affiliated institutions were more likely to publish their research presentations as compared to Ministry of Health hospitals (OR 3.1 95% CI 1.4-6.8, p < 0.01). There is a need to encourage publication of local research presentations. University-affiliated institutions performed better due to institution pressure for career advancement.

Serum Eosinophilic Cationic Protein (ECP) in Asthmatic Malaysian Children.

Eosinophilic inflammation in the airways is important in the pathogenesis of childhood asthma. Serum eosinophilic cationic protein (ECP), a marker of eosinophil activation was measured in 20 asthmatic children and 19 non-asthmatic controls. There was no difference in the socio-demography, passive smoke exposure, urinary cotinine levels and family history of asthma between the 2 groups. The median serum ECP in asthmatic children was 27.0 mcg/L (IQ1 8.8, IQ3 59.0); which was higher than in non-asthmatic controls [5.9 mcg/L (IQ1 3.0, IQ3 11.9), p=0.002]. An elevated serum ECP level can be helpful as supportive evidence in the diagnosis of bronchial asthma in Malaysia children.

Risk factors for hypoxemia and respiratory failure in respiratory syncytial virus bronchiolitis.

Respiratory syncytial virus (RSV) bronchiolitis is a common infection in young children and may result in hospitalization. We examined the incidence of, and risk factors associated with, hypoxemia and respiratory failure in 216 children aged < 24 months admitted consecutively for proven RSV bronchiolitis. Hypoxemia was defined as SpO2 < 90% in room air and severe RSV bronchiolitis requiring intubation and ventilation was categorized as respiratory failure. Corrected age at admission was used for premature children (gestation < 37 weeks). Hypoxemia was suffered by 31 (14.3%) children. It was more likely to occur in children who were Malay (OR 2.56, 95%CI 1.05-6.23, p=0.03) or premature (OR 6.72, 95%CI 2.69-16.78, p<0.01). Hypoxemia was also more likely to develop in children with failure to thrive (OR 2.96, 95%CI 1.28-6.82, p<0.01). The seven (3.2%) children who were both premature (OR 11.94, 95%CI 2.50-56.99, p<0.01) and failure to thrive (OR 6.41, 95%CI 1.37-29.87, p=0.02) were more likely to develop respiratory failure. Prematurity was the only significant risk factor for hypoxemia and respiratory failure by logistic regression analysis (OR 1.17, 95%CI 1.06-1.55, p<0.01 and OR 1.14 95%CI 1.02-2.07, p=0.02 respectively). Prematurity was the single most important risk factor for both hypoxemia and respiratory failure in RSV bronchiolitis.