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1.
Heliyon ; 10(3): e25220, 2024 Feb 15.
Article in English | MEDLINE | ID: mdl-38333800

ABSTRACT

Macroalgal blooms (Green tides) are occurring more frequently in many regions of the world because of the combined effects of increasingly intense human activity and climate change. In the last decade, the world's largest Ulva prolifera green tide has become a recurrent phenomenon, appearing every summer in the southern Yellow Sea, China. Green tides can hurt coastal tourism and eradicate aquaculture and artisanal fishing. Eutrophication in nearshore waters is the ultimate explanation for the explosive growth of the macroalgal biomass, but the specific course of each nearshore green tide is often complex and requires in-depth and extensive research to develop effective mitigation strategies. Researchers have undertaken extensive studies on the prevention, control and mitigation of large-scale green algal blooms, and felicitated the utilization of green tide harmful biomass through bio-refining, bioconversion and other measures. However, due to the large-scale and trans-regional nature of the green tide, the government's administrative coordination measures are also essential for effective control. Nevertheless, it is becoming increasingly urgent to prevent and control the bloom at the early stage, and efficiently salvage and use these valuable raw materials.

2.
Microbiol Spectr ; 11(4): e0127723, 2023 08 17.
Article in English | MEDLINE | ID: mdl-37404143

ABSTRACT

CRISPR-Cas is an adaptive immune system that allows bacteria to inactivate mobile genetic elements. Approximately 50% of bacteria harbor CRISPR-Cas; however, in the human pathogen Staphylococcus aureus, CRISPR-Cas loci are less common and often studied in heterologous systems. We analyzed the prevalence of CRISPR-Cas in genomes of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated in Denmark. Only 2.9% of the strains carried CRISPR-Cas systems, but for strains of sequence type ST630, over half were positive. All CRISPR-Cas loci were type III-A and located within the staphylococcal cassette chromosome mec (SCCmec) type V(5C2&5), conferring ß-lactam resistance. Curiously, only 23 different CRISPR spacers were identified in 69 CRISPR-Cas positive strains, and almost identical SCCmec cassettes, CRISPR arrays, and cas genes are present in staphylococcal species other than S. aureus, suggesting that these were transferred horizontally. For the ST630 strain 110900, we demonstrate that the SCCmec cassette containing CRISPR-Cas is excised from the chromosome at high frequency. However, the cassette was not transferable under the conditions investigated. One of the CRISPR spacers targets a late gene in the lytic bacteriophage phiIPLA-RODI, and we show that the system protects against phage infection by reducing phage burst size. However, CRISPR-Cas can be overloaded or circumvented by CRISPR escape mutants. Our results imply that the endogenous type III-A CRISPR-Cas system in S. aureus is active against targeted phages, albeit with low efficacy. This suggests that native S. aureus CRISPR-Cas offers only partial immunity and in nature may work in tandem with other defense systems. IMPORTANCE CRISPR-Cas is an adaptive immune system protecting bacteria and archaea against mobile genetic elements such as phages. In strains of Staphylococcus aureus, CRISPR-Cas is rare, but when present, it is located within the SCCmec element, which encodes resistance to methicillin and other ß-lactam antibiotics. We show that the element is excisable, suggesting that the CRISPR-Cas locus is transferable. In support of this, we found almost identical CRISPR-Cas-carrying SCCmec elements in different species of non-S. aureus staphylococci, indicating that the system is mobile but only rarely acquires new spacers in S. aureus. Additionally, we show that in its endogenous form, the S. aureus CRISPR-Cas is active but inefficient against lytic phages that can overload the system or form escape mutants. Thus, we propose that CRISPR-Cas in S. aureus offers only partial immunity in native systems and so may work with other defense systems to prevent phage-mediated killing.


Subject(s)
Bacteriophages , Methicillin-Resistant Staphylococcus aureus , Staphylococcal Infections , Humans , Staphylococcus aureus/genetics , Methicillin-Resistant Staphylococcus aureus/genetics , CRISPR-Cas Systems , Bacteriophages/genetics , Staphylococcus/genetics , Staphylococcal Infections/microbiology , Chromosomes , Cell Proliferation , Chromosomes, Bacterial
4.
Chemosphere ; 335: 138962, 2023 Sep.
Article in English | MEDLINE | ID: mdl-37230304

ABSTRACT

Human activities can cause zinc (Zn) contamination of aquatic environments. Zn is an essential trace metal, but effects of environmentally relevant Zn exposure on the brain-intestine axis in fish are poorly understood. Here, six-month-old female zebrafish (Danio rerio) were exposed to environmentally relevant Zn concentrations for six weeks. Zn significantly accumulated in the brain and intestine, causing anxiety-like behaviors and altered social behaviors. Zn accumulation altered levels of neurotransmitters, including serotonin, glutamate, and γ-aminobutyric acid, in the brain and intestine, and these changes were directly associated with changes in behavior. Zn caused oxidative damage and mitochondrial dysfunction, and impaired NADH dehydrogenase, thereby dysregulating the energy supply in brain. Zn exposure resulted in nucleotide imbalance and dysregulation of DNA replication and the cell cycle, potentially impairing the self-renewal of intestinal cells. Zn also disturbed carbohydrate and peptide metabolism in the intestine. These results indicate that chronic exposure to Zn at environmentally relevant concentrations dysregulates the bidirectional interaction of the brain-intestine axis with respect to neurotransmitters, nutrients, and nucleotide metabolites, thereby causing neurological disorder-like behaviors. Our study highlights the necessity to evaluate the negative impacts of chronic environmentally relevant Zn exposure on the health of humans and aquatic animals.


Subject(s)
Water Pollutants, Chemical , Zebrafish , Animals , Female , Humans , Infant , Zebrafish/metabolism , Zinc/metabolism , Brain/metabolism , Nucleotides/metabolism , Neurotransmitter Agents/metabolism , Water Pollutants, Chemical/toxicity , Water Pollutants, Chemical/metabolism
6.
J Phys Condens Matter ; 35(23)2023 Mar 27.
Article in English | MEDLINE | ID: mdl-36913735

ABSTRACT

Bi4Br4is a quasi-one-dimensional van der Waals topological insulator with novel electronic properties. Several efforts have been devoted to the understanding of its bulk form, yet it remains a challenge to explore the transport properties in low-dimensional structures due to the difficulty of device fabrication. Here we report for the first time a gate-tunable transport in exfoliated Bi4Br4nanobelts. Notable two-frequency Shubnikov-de Haas oscillations oscillations are discovered at low temperatures, with the low- and high-frequency parts coming from the three-dimensional bulk state and the two-dimensional surface state, respectively. In addition, ambipolar field effect is realized with a longitudinal resistance peak and a sign reverse in the Hall coefficient. Our successful measurements of quantum oscillations and realization of gate-tunable transport lay a foundation for further investigation of novel topological properties and room-temperature quantum spin Hall states in Bi4Br4.

7.
Adv Sci (Weinh) ; 10(9): e2206574, 2023 Mar.
Article in English | MEDLINE | ID: mdl-36683228

ABSTRACT

Transition metal oxides with high capacity still confront the challenges of low initial coulombic efficiency (ICE, generally <70%) and inferior cyclic stability for practical lithium-storage. Herein, a hollow slender carambola-like Li0.43 FeO1.51 with Fe vacancies is proposed by a facile reaction of Fe3+ -containing metal-organic frameworks with Li2 CO3 . Synthesis experiments combined with synchrotron-radiation X-ray measurements identify that the hollow structure is caused by Li2 CO3 erosion, while the formation of Fe vacancies is resulted from insufficient lithiation process with reduced Li2 CO3 dosage. The optimized lithium iron oxides exhibit remarkably improved ICE (from 68.24% to 86.78%), high-rate performance (357 mAh g-1 at 5 A g-1 ), and superior cycling stability (884 mAh g-1 after 500 cycles at 0.5 A g-1 ). Paring with LiFePO4 cathodes, the full-cells achieve extraordinary cyclic stability with 99.3% retention after 100 cycles. The improved electrochemical performances can be attributed to the synergy of structural characteristics and Fe vacancy engineering. The unique hollow structure alleviates the volume expansion of Li0.43 FeO1.51 , while the in situ generated Fe vacancies are powerful for modulating electronic structure with boosted Li+ transport rate and catalyze more Li2 O decomposition to react with Fe in the first charge process, hence enhancing the ICE of lithium iron oxide anode materials.

8.
Chem Commun (Camb) ; 59(3): 346-349, 2023 Jan 03.
Article in English | MEDLINE | ID: mdl-36514971

ABSTRACT

The designed synthesis of chiral luminescent molecules with excellent circularly polarized luminescence (CPL) performance and high quantum yield (QY) levels has attracted great interest but remains very challenging. Herein, we report three pairs of chiral europium-titanium-oxo clusters featuring both modest CPL characteristics and high QY levels (up to 79%), which can be regulated by switching between different ligand substituents.


Subject(s)
Europium , Titanium , Luminescence
9.
Food Chem ; 406: 135004, 2023 Apr 16.
Article in English | MEDLINE | ID: mdl-36481514

ABSTRACT

The health benefits of quercetin are limited by its low bioaccessibility. This could be improved by developing plant-based protein delivery systems. Encapsulating quercetin using untreated and high-intensity ultrasound treated (20 kHz at 139 W for 10, 15 and 20 min) soy protein isolate (SPI) produced composite nanoparticles at around 127-136 nm. Ultrasound treatments on SPI caused structural changes of proteins (e.g. around 6-fold increase of surface hydrophobicity and protein solubility) favorable to encapsulation. The encapsulation efficiency for quercetin complexed with 15 min ultrasound treated SPI (76.5 %) was around 10-fold of that with the native SPI (7.2 %). Quercetin was significantly more in vitro bioaccessible when complexed with the treated SPI (61.1 %-64.5 %), as compared to the free quercetin (10.5 %-13.0 %). Ultrasound treated SPI seems to be a promising nanocarrier to encapsulate hydrophobic bioactive ingredients with higher solubility, stability, and bioaccessibility.


Subject(s)
Nanoparticles , Quercetin , Quercetin/chemistry , Soybean Proteins/chemistry , Nanoparticles/chemistry , Solubility , Hydrophobic and Hydrophilic Interactions
10.
J Pharm Sci ; 112(2): 562-572, 2023 02.
Article in English | MEDLINE | ID: mdl-36096286

ABSTRACT

Vaginal candidiasis is a common form of infection in women caused by Candida species. Due to several drawbacks of conventional treatments, the current research is attempted to formulate and optimize a miconazole nitrate-loaded in situ spray gel for vaginal candidiasis. The stimuli-responsive (pH and thermo-responsive) polymers selected for the in situ gel were chitosan and poloxamer 407, respectively, whereas hydroxypropyl methylcellulose (HPMC) was introduced in the formulation to further improve the mucoadhesive property. The dispersion of each polymer was carried out using the cold method, whereas the optimization of the formulation was achieved using Box-Behnken statistical design considering viscosity and gelation temperature as dependent variables. Present design achieved the optimized outcome with HPMC, poloxamer and chitosan at 0.52% (w/v), 18.68% (w/v) and 0.41% (w/v), respectively. Evaluation of drug-excipients compatibility was performed using differential scanning calorimetry, Fourier transform infrared spectroscopy, and thermogravimetric analysis where the results showed the absence of any chemical interaction between the polymers and drug component. The optimized formulation showed gelation temperature at 31°C allowing in situ phase transition in a vaginal environment; pH of 4.21 is suitable for use in the vaginal cavity, and appropriate viscosity (290 cP) at storage temperature (below 30°C) would allow spraying at ease, whereas strong mucoadhesive force (22.4±0.513 g) would prevent leaking of the formulation after application. The drug release profile showed sustained release up to 24 h with a cumulative drug release of 81.72%, which is significantly better than the marketed miconazole nitrate cream. In addition, an improved antifungal activity could be correlated to the sustained release of the drug from the formulation. Finally, the safety of the formulation was established while tested on HaCaT cell lines. Based on our findings, it could be concluded that the in situ hydrogel formulation using stimuli-responsive polymers could be a viable alternative to the conventional dosage form that can help to reduce the frequency of administration with ease of application to the site of infection, thus will provide better patient compliance.


Subject(s)
Candidiasis, Vulvovaginal , Chitosan , Female , Humans , Miconazole/chemistry , Miconazole/therapeutic use , Delayed-Action Preparations/chemistry , Chitosan/chemistry , Candidiasis, Vulvovaginal/drug therapy , Antifungal Agents/chemistry , Poloxamer/chemistry , Gels/chemistry
11.
Article in English | WPRIM (Western Pacific) | ID: wpr-972338

ABSTRACT

@#Airway management is important for critically ill patients. Improper airway management can directly threaten the life of patients.[1] Early correct airway assessment and effective airway management can improve patient prognosis.[2] Coughing ability plays an important role in the decision-making process of airway management. Patients with impaired coughing ability have a higher risk of tracheal intubation during treatment. The concept of cough strength was first proposed by Khamiees in 2001,[3] but the evaluation criteria did not include coughing ability. The purpose of this study was to assess patients’ coughing ability through the Delphi method and expert consultation, to provide data support for establishing a cough reflex intensity score and to construct an advanced airway management model for quick and effective evaluation.[4,5]

12.
Ecotoxicol Environ Saf ; 248: 114303, 2022 Dec 15.
Article in English | MEDLINE | ID: mdl-36403304

ABSTRACT

Zinc is an essential nutrient for life, but over-accumulation can result in toxicity. Anthropogenic activities can increase zinc concentrations in aquatic environments (e.g., to ∼0.46-1.00 mg/L), which are above the safe level of 0.1 mg/L. We investigated the behavior and physiology of zebrafish (Danio rerio) in response to environment-related exposure to zinc chloride at 0.0 (Ctrl), 1.0 (ZnCl2-low) and 1.5 (ZnCl2-high) mg/L for 6 weeks (the zinc conversion ratio of zinc chloride is ∼0.48 and the nominal (measured) values were: Ctrl, 0 (∼0.01); ZnCl2-low, 0.48 (∼0.51); ZnCl2-high, 0.72 (∼0.69) mg/L). Low-zinc exposure resulted in significantly increased locomotion and fast moving behaviors, while high-zinc exposure resulted in significantly increased aggression and freezing frequency. Single cell RNA-seq of neurons, astrocytes, and oligodendrocytes of the brain revealed expression of genes related to ion transport, neuron generation, and immunomodulation that were heterogeneously regulated by zinc exposure. Astrocyte-induced central nervous system inflammation potentially integrated neurotoxicity and behavior. Integrated analyses of brain and hepatic transcriptional signatures showed that genes (and pathways) dysregulated by zinc were associated with sensory functions, circadian rhythm, glucose and lipid metabolism, and amyloid ß-protein clearance. Our results showed that environment-related zinc contamination can be heterogeneously toxic to brain cells and can disturb coordination of brain-liver physiology. This may disrupt neurobehavior and cause a neurodegeneration-like syndrome in adult zebrafish.


Subject(s)
Chronobiology Disorders , Zebrafish , Animals , Zinc/toxicity , Amyloid beta-Peptides , Brain , Aggression , Liver
13.
Sci Total Environ ; 848: 157724, 2022 Nov 20.
Article in English | MEDLINE | ID: mdl-35914606

ABSTRACT

The study of the fate of organophosphate esters (OPEs) in the interior environment is vital because of the growing use of OPEs. Organic films on glass are both sink and sources of indoor pollutants. Indoor window films have been employed as passive air samplers to collect OPEs in the indoor air. Nevertheless, little is known about the development and equilibrium condition of OPEs on indoor window films during the film formation process. In this study, the concentrations of twelve OPEs in indoor window films from different buildings on a university campus and the growth thickness of the films as a function of sampling time were investigated in different seasons. Ten out of the 12 OPEs were detected in window film with >50 % frequency. Tris (2-chloroethyl) phosphate (TCEP) and tris (1-chloro-2-propyl) phosphate (TCPP), which are chlorinated and toxic OPEs, were the dominant OPEs found in the winter. The majority of OPEs in window films exhibited linear growth patterns within 77 days. Temperature, humidity, ventilation, and seasonality all affected the concentrations of various OPEs in the window films. Low molecular weight OPEs, such as tri-n-butyl phosphate and TCEP, attained equilibrium between indoor air and window films within 49 or 77 days. The indoor air concentrations of OPEs were estimated from their film concentrations based on the theoretical approach for the passive air sampler. In winter, the predicted gas-phase air concentrations of OPEs (3.7 ng/m3 for TECP) were significantly lower than or comparable to summer (11 ng/m3, p < 0.05). To the best of our knowledge, this is the first attempt to combine uncertainty and sensitivity analysis to understand the behaviors of OPEs in indoor film and air.


Subject(s)
Environmental Pollutants , Flame Retardants , Environmental Monitoring , Environmental Pollutants/analysis , Esters/analysis , Flame Retardants/analysis , Humans , Organophosphates/analysis , Phosphates/analysis , Phosphines
14.
J Adv Vet Anim Res ; 9(2): 275-281, 2022 Jun.
Article in English | MEDLINE | ID: mdl-35891657

ABSTRACT

Objective: This short study describes the occurrence of pathogenic Leptospira spp. in two major wet markets in Kota Bharu, Kelantan, Malaysia. Materials and Methods: 30 rodents (20 rats and 10 shrews) were caught in 2 wet markets, and a postmortem was performed to extract both kidneys. Molecular diagnosis via polymerase chain reaction (PCR) was conducted to detect leptospiral DNA using universal and pathogenic Leptospira primers, respectively. Results: The results showed that 20/28 (72%) rat samples were detected positive for Leptospira spp, and all shrews were negative. Further sequencing analysis identified L. interrogans and L. borgpetersenii as the most frequently Leptospirosis species from kidney samples. Conclusions: The presented study here sheds light on the presence of pathogenic leptospires harboring the rat population in both wet markets in Kelantan, which presents a great public health risk to wet market workers and visitors.

15.
Spectrochim Acta A Mol Biomol Spectrosc ; 274: 121107, 2022 Jun 05.
Article in English | MEDLINE | ID: mdl-35259706

ABSTRACT

Vibrational properties associated with the intra- and intermolecular bonding of the crystalline Dibenz[a,h]anthracene at low temperatures are investigated by Raman scattering. A complete characterization of phonon spectra is given for this material. In the 120-150 K temperature region, several lattice modes show abrupt changes of splitting and the discontinuities in the temperature shift, but no emergence of new modes. Moreover, the intensity ratio of I68/38 is greater than 1 below 130 K. Meanwhile, the aromatic C-C stretching modes exhibit anomalous behaviors in frequencies, widths, and intensities at about 130 K. These spectroscopic results demonstrate a disorder-order transition occurred at about 130 K. However, the modes, corresponding to C-H out-of-plane bending, C-H in-plane bending, and/or C-H rocking, have no significant change in the whole temperature range. It indicates that the transition mainly results from the change of the tilt angle between the molecules. Our work is of great significance to understand the internal vibrational properties of Dibenz[a,h]anthracene, and it also provides considerable supports for the further study of this material.

16.
Sci Total Environ ; 828: 154099, 2022 Jul 01.
Article in English | MEDLINE | ID: mdl-35240190

ABSTRACT

Anthropogenic activities discharge zinc into aquatic ecosystems, and the effects of long-term and low-concentration zinc exposure on fish behavior are unclear. We evaluated the behavior and physiology of male zebrafish (Danio rerio) after a 6-week exposure to 1.0 or 1.5 ppm (mg/L) zinc chloride. The exposure caused anxiety-like behaviors and altered the social preferences in both exposure groups. Analysis of transcriptional changes suggested that in the brain, zinc exerted heterogenetic effects on immune and neurotransmitter functions. Exposure to 1.0 ppm zinc chloride resulted in constitutive immune dyshomeostasis, while exposure to 1.5 ppm zinc chloride impaired the neurotransmitter glutamate. In the intestine, zinc dysregulated self-renewal of intestinal cells, a potential loss of defense function. Moreover, exposure to 1.5 ppm zinc chloride suppressed intestinal immune functions and dysregulated tyrosine metabolism. These behavioral alterations suggested that the underlying mechanisms were distinct and concentration-specific. Overall, environmental levels of zinc can alter male zebrafish behaviors by dysregulating neurotransmitter and immunomodulation signatures.


Subject(s)
Water Pollutants, Chemical , Zebrafish , Animals , Behavior, Animal , Ecosystem , Homeostasis , Male , Neurotransmitter Agents/metabolism , Phenotype , Water Pollutants, Chemical/metabolism , Zebrafish/physiology , Zinc/metabolism
17.
Clin Infect Dis ; 75(1): e35-e43, 2022 08 24.
Article in English | MEDLINE | ID: mdl-35323887

ABSTRACT

BACKGROUND: In Singapore, quarantine of all close contacts with entry and exit polymerase chain reaction testing enabled evaluation of the impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination and pediatric age on transmission of the Delta variant. METHODS: This retrospective cohort study included all household close contacts between 1 March 2021 and 31 August 2021. RESULTS: Among 8470 Delta variant-exposed contacts linked to 2583 indices, full-vaccination of the index with BNT162b2 or mRNA-1273 was associated with reduction in acquisition by contacts (adjusted odds ratio [aOR], 0.56; 95% robust confidence interval [RCI], .44-.71 and aOR, 0.51; 95% RCI, .27-.96, respectively). Compared with young adults (aged 18-29 years), children (aged 0-11 years) were significantly more likely to transmit (aOR, 2.37; 95% RCI, 1.57-3.60) and acquire (aOR, 1.43; 95% RCI, 1.07-1.93) infection, vaccination considered. Longer duration from vaccination completion among contacts was associated with decline in protection against acquisition (first-month aOR, 0.42; 95% RCI, .33-.55; fifth-month aOR, 0.84; 95% RCI, .55-.98; P < .0001 for trend) and symptomatic disease (first-month aOR, 0.30; 95% RCI, .23-.41; fifth-month aOR, 0.62; 95% RCI, .38-1.02; P < .0001 for trend). Contacts immunized with mRNA-1273 had significant reduction in acquisition (aOR, 0.73; 95% RCI, .58-.91) compared with BNT162b2. CONCLUSIONS: Among household close contacts, vaccination prevented onward SARS-CoV-2 transmission and there was in-creased risk of SARS-CoV-2 acquisition and transmission among children compared with young adults. Time after completion of vaccination and vaccine type affected SARS-CoV-2 acquisition.


Subject(s)
COVID-19 , SARS-CoV-2 , Adolescent , Adult , BNT162 Vaccine , COVID-19/epidemiology , COVID-19/prevention & control , Child , Child, Preschool , Humans , Infant , Infant, Newborn , Retrospective Studies , SARS-CoV-2/genetics , Vaccination , Young Adult
18.
Mar Biotechnol (NY) ; 24(2): 354-365, 2022 Apr.
Article in English | MEDLINE | ID: mdl-35305189

ABSTRACT

Heat shock procedure is crucial for gynogenetic manipulation leading to diploidization of the maternal genomes; however, the underlying molecular mechanism especially the transcriptomic changes during this procedure has still not been unveiled yet. Here, the artificial gynogenesis of zebrafish (Danio rerio) using inactivated sperm from rare minnow (Gobiocypris rarus) was conducted. We found that artificial gynogenetic manipulation, including pseudo-fertilization and heat shock, decreased hatching rates, whereas heat shock treatment alone had medium hatching rates. The first cleavage changed the expression of genes associated with RNA transcription and protein synthesis. A co-expression network regulated by hub genes GIT1, Sepsecs, and FLNB was significantly correlated with heat shock procedure. The cyclin family and cyclin-dependent kinase-related genes were lowly expressed in embryos from gynogenetic zebrafish, and genes involved in controlling the cell cycle and genomic stability were significantly altered by the gynogenetic treatment. Our results show the effects of artificial gynogenesis on embryos and describe changes in gene expression that suggest drastic changes take place in cell division by heat shock procedure. These findings will contribute to an understanding of the molecular basis for germplasm improving, including the purifying effect and allogynogenetic biological effect by gynogenesis.


Subject(s)
Cyprinidae , Zebrafish , Animals , Cell Division , Cyprinidae/genetics , Heat-Shock Response/genetics , Male , Spermatozoa , Zebrafish/genetics
19.
J ASEAN Fed Endocr Soc ; 36(2): 216-219, 2021.
Article in English | MEDLINE | ID: mdl-34966209

ABSTRACT

We present a 61-year-old Chinese female who had a history of angioinvasive follicular thyroid cancer (FTC) treated with total thyroidectomy 16 years ago, without radioactive iodine (RAI) treatment who now presents with de novo pretibial myxedema (PTM) followed by active severe Graves' ophthalmopathy (GO) requiring pulse steroids and radiotherapy.

20.
Lancet Reg Health West Pac ; 17: 100299, 2021 Dec.
Article in English | MEDLINE | ID: mdl-34746899

ABSTRACT

BACKGROUND: Impact of the Delta variant and vaccination on SARS-CoV-2 transmission remains unclear. In Singapore, quarantine of all close contacts, including entry and exit PCR testing, provided the opportunity to determine risk of infection by the Delta variant compared to other variants, vaccine efficacy against SARS-CoV-2 acquisition, symptomatic or severe COVID-19, and risk factors associated with SARS-CoV-2 acquisition and symptomatic disease. METHODS: This retrospective cohort study included all close contacts between September 1, 2020 and May 31, 2021. Regardless of symptoms, all were quarantined for 14 days with entry and exit PCR testing. Household contacts were defined as individuals who shared a residence with a Covid-19 index case. Secondary attack rates among household close contacts of Delta variant-infected indexes and other variant-infected indexes were derived from prevalence of diagnosed cases among contacts. Relative risk ratios and bootstrapping at the cluster level was used to determine risk of infection by the Delta variant compared to other variants and vaccine efficacy against SARS-CoV-2 acquisition, symptomatic or severe COVID-19. Logistic regression using generalized estimating equations was used to determine risk factors associated with SARS-CoV-2 acquisition and symptomatic disease. FINDINGS: Of 1024 household contacts linked to 301 PCR-confirmed index cases, 753 (73.5%) were linked to Delta-infected indexes and 248 (24.2%) were exposed to indexes with other variants. Household secondary attack rate among unvaccinated Delta-exposed contacts was 25.8% (95% boostrap confidence interval [BCI] 20.6-31.5%) compared with 12.9% (95%BCI 7.0-20.0%) among other variant-exposed contacts. Unvaccinated Delta-exposed contacts were more likely to be infected than those exposed to other variants (Relative risk 2.01, 95%CI 1.24-3.84). Among Delta-exposed contacts, complete vaccination had a vaccine effectiveness of 56.4% (95%BCI 32.6-75.8%) against acquisition, 64.1% (95%BCI 37.8-85.4%) against symptomatic disease and 100% against severe disease. Among Delta-exposed contacts, vaccination status (adjusted odds ratio [aOR] 0.33, 95% robust confidence interval [RCI] 0.17-0.63) and older age of the index (aOR 1.20 per decade, 95%RCI 1.03-1.39) was associated with increased risk of SARS-CoV-2 acquisition by the contact. Vaccination status of the index was not associated with a statistically-significant difference for contact SARS-CoV-2 acquisition (aOR 0.73, 95%RCI 0.38-1.40). INTERPRETATION: Increased risk of SARS-CoV-2 Delta acquisition compared with other variants was reduced with vaccination. Close-contacts of vaccinated Delta-infected indexes did not have statistically significant reduced risk of acquisition compared with unvaccinated Delta-infected indexes.

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