Border Control for Infectious Respiratory Disease Pandemics: A Modelling Study for H1N1 and Four Strains of SARS-CoV-2.

Post-pandemic economic recovery relies on border control for safe cross-border movement. Following the COVID-19 pandemic, we investigate whether effective strategies generalize across diseases and variants. For four SARS-CoV-2 variants and influenza A-H1N1, we simulated 21 strategy families of varying test types and frequencies, quantifying expected transmission risk, relative to no control, by strategy family and quarantine length. We also determined minimum quarantine lengths to suppress relative risk below given thresholds. SARS-CoV-2 variants showed similar relative risk across strategy families and quarantine lengths, with at most 2 days' between-variant difference in minimum quarantine lengths. ART-based and PCR-based strategies showed comparable effectiveness, with regular testing strategies requiring at most 9 days. For influenza A-H1N1, ART-based strategies were ineffective. Daily ART testing reduced relative risk only 9% faster than without regular testing. PCR-based strategies were moderately effective, with daily PCR (0-day delay) testing requiring 16 days for the second-most stringent threshold. Viruses with high typical viral loads and low transmission risk given low viral loads, such as SARS-CoV-2, are effectively controlled with moderate-sensitivity tests (ARTs) and modest quarantine periods. Viruses with low typical viral loads and substantial transmission risk at low viral loads, such as influenza A-H1N1, require high-sensitivity tests (PCR) and longer quarantine periods.

Cost benefit analysis of alternative testing and quarantine policies for travelers for infection control: A case study of Singapore during the COVID-19 pandemic.

Background: Border control mitigates local infections but bears a heavy economic cost, especially for tourism-reliant countries. While studies have supported the efficacy of border control in suppressing cross-border transmission, the trade-off between costs from imported and secondary cases and from lost economic activities has not been studied. This case study of Singapore during the COVID-19 pandemic aims to understand the impacts of varying quarantine length and testing strategies on the economy and health system. Additionally, we explored the impact of permitting unvaccinated travelers to address emerging equity concerns. We assumed that community transmission is stable and vaccination rates are high enough that inbound travelers are not dissuaded from traveling. Methods: The number of travelers was predicted considering that longer quarantine reduces willingness to travel. A micro-simulation model predicted the number of COVID-19 cases among travelers, the resultant secondary cases, and the probability of being symptomatic in each group. The incremental net monetary benefit (INB) of Singapore was quantified under each border-opening policy compared to pre-opening status, based on tourism receipts, cost/profit from testing and quarantine, and cost and health loss due to COVID-19 cases. Results: Compared to polymerase chain reaction (PCR), rapid antigen test (ART) detects fewer imported cases but results in fewer secondary cases. Longer quarantine results in fewer cases but lower INB due to reduced tourism receipts. Assuming the proportion of unvaccinated travelers is small (8% locally and 24% globally), allowing unvaccinated travelers will accrue higher INB without exceeding the intensive care unit (ICU) capacity. The highest monthly INB from all travelers is $2,236.24 m, with 46.69 ICU cases per month, achieved with ARTs at pre-departure and on arrival without quarantine. The optimal policy in terms of highest INB is robust under changes to various model assumptions. Among all cost-benefit components, the top driver for INB is tourism receipts. Conclusions: With high vaccination rates locally and globally alongside stable community transmission, opening borders to travelers regardless of vaccination status will increase economic growth in the destination country. The caseloads remain manageable without exceeding ICU capacity, and costs of cases are offset by the economic value generated from travelers.

Economic Analysis of Border Control Policies during COVID-19 Pandemic: A Modelling Study to Inform Cross-Border Travel Policy between Singapore and Thailand.

With countries progressing towards high COVID-19 vaccination rates, strategies for border reopening are required. This study focuses on Thailand and Singapore, two countries that share significant tourism visitation, to illustrate a framework for optimizing COVID-19 testing and quarantine policies for bilateral travel with a focus on economic recovery. The timeframe is the month of October 2021, when Thailand and Singapore were preparing to reopen borders for bilateral travel. This study was conducted to provide evidence for the border reopening policy decisions. Incremental net benefit (INB) compared to the pre-opening period was quantified through a willingness-to-travel model, a micro-simulation COVID-19 transmission model and an economic model accounting for medical and non-medical costs/benefits. Multiple testing and quarantine policies were examined, and Pareto optimal (PO) policies and the most influential components were identified. The highest possible INB for Thailand is US $125.94 million, under a PO policy with no quarantine but with antigen rapid tests (ARTs) pre-departure and upon arrival to enter both countries. The highest possible INB for Singapore is US $29.78 million, under another PO policy with no quarantine on both sides, no testing to enter Thailand, and ARTs pre-departure and upon arrival to enter Singapore. Tourism receipts and costs/profits of testing and quarantine have greater economic impacts than that from COVID-19 transmission. Provided healthcare systems have sufficient capacity, great economic benefits can be gained for both countries by relaxing border control measures.

Analysis of COVID-19 Incidence and Severity Among Adults Vaccinated With 2-Dose mRNA COVID-19 or Inactivated SARS-CoV-2 Vaccines With and Without Boosters in Singapore.

Importance: Assessing booster effectiveness of COVID-19 mRNA vaccine and inactivated SARS-CoV-2 vaccine over longer time intervals and in response to any further SARS-CoV-2 variants is crucial in determining optimal COVID-19 vaccination strategies. Objective: To determine levels of protection against severe COVID-19 and confirmed SARS-CoV-2 infection by types and combinations of vaccine boosters in Singapore during the Omicron wave. Design, Setting, and Participants: This cohort study included Singapore residents aged 30 years or more vaccinated with either at least 2 doses of mRNA COVID-19 vaccines (ie, Pfizer-BioNTech BNT162b2 or Moderna mRNA-1273) or inactivated SARS-CoV-2 vaccines (Sinovac CoronaVac or Sinopharm BBIBP-CorV) as of March 10, 2022. Individuals with a known SARS-CoV-2 infection prior to December 27, 2021, an infection on or before the date of their second vaccine dose, or with reinfection cases were excluded. Exposures: Two or 3 doses of Pfizer-BioNTech BNT162b2, Moderna mRNA-1273, Sinovac CoronaVac, or Sinopharm BBIBP-CorV. Main Outcomes and Measures: Notified infections from December 27, 2021, to March 10, 2022, adjusted for age, sex, race, housing status, and calendar days. Estimated booster effectiveness, defined as the relative incidence-rate reduction of severe disease (supplemental oxygen, intensive care, or death) or confirmed infection following 3-dose vaccination compared with 5 months after second mRNA dose, was determined using binomial regression. Results: Among 2 441 581 eligible individuals (1 279 047 [52.4%] women, 846 110 (34.7%) aged 60 years and older), there were 319 943 (13.1%) confirmed SARS-CoV-2 infections, of which 1513 (0.4%) were severe COVID-19 cases. mRNA booster effectiveness against confirmed infection 15 to 60 days after boosting was estimated to range from 31.7% to 41.3% for the 4 boosting combinations (homologous BNT162b2, homologous mRNA-1273, 2-dose BNT162b2/mRNA-1273 booster, and 2-dose mRNA-1273/BNT162b2 booster). Five months and more after boosting, estimated booster effectiveness against confirmed infection waned, ranging from -2.8% to 14.6%. Against severe COVID-19, estimated mRNA booster effectiveness was 87.4% (95% CI, 83.3%-90.5%) 15 to 60 days after boosting and 87.2% (95% CI, 84.2%-89.7%) 5 to 6 months after boosting, with no significant difference comparing vaccine combinations. Booster effectiveness against severe COVID-19 15 days to 330 days after 3-dose inactivated COVID-19 vaccination, regardless of combination, was estimated to be 69.6% (95% CI, 48.7%-81.9%). Conclusions and Relevance: Booster mRNA vaccine protection against severe COVID-19 was estimated to be durable over 6 months. Three-dose inactivated SARS-CoV-2 vaccination provided greater protection than 2-dose but weaker protection compared with 3-dose mRNA.

Assessment of Depression, Anxiety, and Quality of Life in Singaporean Patients With Glaucoma.

PURPOSE: To determine the prevalence and risk factors for anxiety disorder and depression among glaucoma patients in Singapore, and to assess the relationship between quality of life (QOL) and depression/anxiety. METHODS: In this cross-sectional study, glaucoma patients aged 21 and above with a known diagnosis of primary open-angle glaucoma or primary angle-closure glaucoma were recruited from a tertiary care hospital. Patients with other types of glaucoma, and coexisting ocular or psychiatric disorders were excluded.Ophthalmic examination was carried out on all participants, which included best-corrected visual acuity (BCVA), intraocular pressure (IOP), gonioscopy, standard automated perimetry, and optic disc evaluation. Sociodemographic information and treatment histories were also collected.The Hamilton Depression Rating Scale (HAM-D), Hamilton Anxiety Rating Scale (HAM-A), and Visual Function Questionnaire (VFQ25) were administered to evaluate for depression, anxiety, and impact on QOL, respectively. RESULTS: A total of 100 patients were included in this study. The mean age was 67.1±12.0 years (range, 24 to 90 y). The frequency of depression and anxiety among our patients was 30% and 64%, respectively. The mean HAM-D score was 4.37±4.17 (range, 0 to 17), whereas the mean HAM-A score was 2.38±2.80 (range, 0 to 13). The mean VFQ25 score was 78.8±16.0 (range, 42.4 to 97.0). The poorest subscale on the VFQ25 was driving, with a mean score of 42.4±42.6 (range, 0.0 to 100.0).We did not find any significant difference between the presence of depression/anxiety between patients with primary open-angle glaucoma (P=0.263) and primary angle-closure glaucoma (P=0.830). Risk factors for depression included: female sex (P=0.020), higher logMAR BCVA in the worse eye (P=0.004), higher cup-disc ratio (P=0.016), lower MD in the better and worse eye (P=0.022 and 0.001, respectively), and lower mean VFQ25 score (P<0.001). Risk factors for anxiety included: lower MD in the worse eye (P=0.004) and lower mean VFQ25 score (P=0.004). There was also no significant association between the use of topical ß-blockers/carbonic anhydrase inhibitors with depression (P=0.793) or anxiety (P=0.282). CONCLUSIONS: There is a relatively high prevalence of depression (30%) and anxiety disorders (64%) among glaucoma patients in Singapore. Female glaucoma patients are more likely to suffer from depression. Other risk factors for depression include higher cup-disc ratio, higher logMAR BCVA, lower MD, and a lower mean VFQ25 score. Risk factors for anxiety disorder include lower MD and lower mean VFQ25 score. Ophthalmologists could consider use of the VFQ25 as an assessment for impairments in QOL in a glaucoma patient. If a glaucoma patient is at high risk of depression or anxiety disorder, a multidisciplinary management approach involving ophthalmology and psychiatry may be required.

Treatment of Dural Carotid-Cavernous Fistulas via the Medial Ophthalmic Vein.

AIM: To present a novel approach to treatment of dural carotid-cavernous fistulas via the medial ophthalmic vein. DESIGN: Retrospective case series. MATERIAL AND METHODS: In this retrospective case series, we present 2 patients (3 eyes) with Type C dural CCFs, who had failed cannulation via the conventional transfemoral route and the transorbital superior ophthalmic vein approach. They subsequently underwent CCF occlusion via an anterior orbital approach through the medial ophthalmic veins, at the Department of Ophthalmology, National University Hospital Singapore. CCF occlusion was confirmed intraoperatively using angiography. Both patients were evaluated postoperatively for best-corrected visual acuity and resolution of clinical signs and symptoms. RESULTS: Successful occlusion of CCFs via the medial ophthalmic veins were achieved in all three orbits, with excellent visual and cosmetic outcomes postoperatively. CONCLUSION: Dural CCFs may potentially lead to severe visual dysfunction and should be diagnosed and treated promptly. When all venous routes have been exhausted, the transorbital approach via the medial ophthalmic vein remains an excellent and viable alternative to access the fistula. Close cooperation between the orbital, anesthetic and radiological teams is essential in ensuring success of the operation.

Thyroid eye disease: a Southeast Asian experience.

AIM: To study the demographics, comorbidities, clinical manifestations and treatment methods of thyroid eye disease (TED) in Singapore. METHODS: In this retrospective case series, we analysed the case records of all patients with TED who presented at our multidisciplinary Thyroid Eye Clinic from November 2002 to October 2012. RESULTS: There were a total of 174 patients-111 female patients (63.8%) and 63 male patients (36.2%). The majority of the patients were ethnically Chinese (80.5%), followed by Malay (10.3%) and Indian (6.3%). The mean age was 40.2 years (SD±15.5, range 0.3-87.0). The commonest sign on ophthalmic examination was eyelid retraction (62.1%), followed by proptosis (61.0%) and lid lag (57.5). Acquired epiblepharon and corneal erosions were noted in 11.5% and 29.3% respectively. Eight patients (4.6%) had dysthyroid optic neuropathy. The mean exophthalmometry reading was 18.8 mm (SD±3.32, range 10.0-28.0). Mild, moderate and severe disease was noted in 71.3%, 20.7% and 8.0% respectively. Thyroid dysfunction was managed with anti-thyroid medication only (40.2%), ß blockers (19.5%), thyroxine replacement (14.4%), radioactive iodine (14.4%) and block-replace regime (9.8%). Clinically significant active orbitopathy was managed with intravenous corticosteroids (12.1%). Surgical procedures consisted of thyroidectomy (10.3%), eyelid surgery (8.6%), orbital decompression (7.5%), epiblepharon correction (2.3%) and strabismus surgery (0.6%). CONCLUSIONS: Corneal erosion secondary to acquired epiblepharon is a common sign in East Asian patients with TED, thus increased awareness among physicians should be encouraged. Mean exophthalmometry values and frequencies of upper eyelid retraction and oedema are lower in East Asian patients compared with Caucasian patients. Among Singapore's multi-ethnic population, Malay patients with TED had the highest exophthalmometry reading.

Pediatric thyroid eye disease--the Singapore experience.

PURPOSE: To identify the demographics, risk factors, clinical manifestations and treatment methods of pediatric thyroid eye disease (TED) in a South-East Asian tertiary referral practice. METHODS: Retrospective case series of all pediatric patients (aged 18 years and under) who presented to our TED clinic between Jan 2006 and Dec 2012. RESULTS: Thirteen patients (26 eyes) were identified - 8 females (61.5%) and 5 males (38.5%), accounting for 6.2% of all TED patients in our practice. Median age was 10.0 years (range, 0.3-18.0). Positive family history was noted in 9 patients (69.2%) and there were no active/passive smokers. Mean follow-up duration was 1.81 years (range, 0-5.2). Common presenting signs included proptosis (92.3%), eyelid retraction (84.6%), acquired epiblepharon (69.2%), corneal erosion (53.8%), and lagophthalmos (53.8%). None had optic neuropathy or strabismus. Mean exophthalmometry was 17.8 mm (SD ± 3.6 mm, range 13.0-27.0). Ten patients (76.9%) had mild disease, 3 patients (23.1%) had moderate disease and none had severe disease. Clinically significant Active disease as defined in adults (VISA Inflammatory Score >4/10), was not observed in any patient. The majority of the patients were treated conservatively. One patient underwent bilateral orbital decompression for severe proptosis, while two patients underwent bilateral lower epiblepharon correction with good outcomes. None required corticosteroids (oral/pulsed). CONCLUSION: Clinical manifestations in pediatric TED are relatively mild and respond well to conservative therapy. Orbital decompression is rarely required but may be considered in children with severe proptosis. Mean exophthalmometry values are lower in East-Asian pediatric TED as compared to Caucasians. Symptomatic acquired epiblepharon, usually associated with keratopathy, is commonly seen in East-Asian pediatric TED; thus, increased awareness among ophthalmologists and pediatricians should be emphasized.

Polymicrobial versus monomicrobial keratitis: a retrospective comparative study.

OBJECTIVES: To compare the risk factors, clinical characteristics, microbiological profile, and treatment outcomes of polymicrobial versus monomicrobial keratitis. METHODS: In this retrospective comparative case series, eyes with polymicrobial and monomicrobial keratitis were identified from microbiological records at a tertiary academic referral center, from January 2002 to December 2010. Only culture positive cases were included. Eyes with infectious keratitis involving two or more pathogens were included in the polymicrobial group, whereas eyes infected solely by Pseudomonas aeruginosa were included in the monomicrobial group. Various parameters including demographics, risk factors, clinical and microbiological characteristics, and treatment outcomes were analyzed. RESULTS: Twenty-one eyes each with polymicrobial and monomicrobial keratitis were included in this study. The mean age of polymicrobial patients was significantly higher than monomicrobials. Use of contact lens was the commonest predisposing factor in both groups. Systemic (23.8%) and multiple (33.3%) risk factors were involved in eyes with polymicrobial keratitis only. The mean size of corneal infiltrates and mean duration for resolvement of infection were significantly greater in the polymicrobial group. Medical treatment was successful only in 80.9% eyes with polymicrobial keratitis, whereas all monomicrobial keratitis patients responded to it. A total of 44 organisms belonging to 18 species (bacteria = 13, fungi = 5) were isolated from the polymicrobial group. P. aeruginosa and Candida albicans were the most frequently isolated bacteria (n = 12) and fungi (n = 5), respectively. In the polymicrobial group, gram-negative organisms were most sensitive to gentamicin (87.8%), followed by ciprofloxacin (78.7%), whereas gram-positive organisms were 100% sensitive to ciprofloxacin and cefazolin. CONCLUSIONS: A high index of suspicion of polymicrobial keratitis should be made in patients with multiple and systemic risk factors. Contact lens usage was the most common risk factor in both groups. Size of corneal infiltrate is a fairly reliable indicator for suspecting polymicrobial keratitis. Prolonged course of the disease and decreased antibiotic sensitivity were the other notable features of polymicrobial keratitis.