Erratum to "Impact of delta variant and vaccination on SARS-CoV-2 secondary attack rate among household close contacts" [The Lancet Regional Health - Western Pacific 17 (2021) 100299].

[This corrects the article DOI: 10.1016/j.lanwpc.2021.100299.].

Compliance with face mask use during the COVID-19 pandemic: a community observational study in Singapore.

Introduction: Widespread mask use is an important intervention for control of the coronavirus disease 2019 pandemic. However, data on the factors affecting mask use are lacking. In this observational study, we evaluated the proportion of and factors influencing face mask use and related hygiene practices. Methods: We observed randomly selected members from the public in 367 venues across Singapore, and recorded the proportion of individuals with full compliance with mask use and mask hygiene (hand hygiene before and after touching the mask or face). Logistic regression analyses were used to determine variables associated with mask and hand hygiene compliance. Results: We made 3,821 observations - 2,149 (56.2%) females, 3,569 (93.4%) adults (≥21 years), 212 (5.5%) children (6-20 years) and 40 (1.0%) children (2-5 years). The overall full compliance rate (correct mask use), poor compliance rate (incorrect mask use) and absent mask use were 84.5%, 12.9% and 2.6%, respectively. The factors - male gender, fabric mask usage and crowded indoor venues - were associated with lower mask compliance. Face or mask touching behaviour was observed in 10.7% and 13.7% of individuals observed, respectively. Only one individual performed hand hygiene before and after touching the mask. Conclusion: The rate of mask compliance was high, probably due to legislation mandating mask usage. However, specific factors and crowded indoor venues associated with lower mask compliance were identified. We also noted an issue with the absence of hand hygiene before and after face or mask touching. These issues may benefit from targeted public health messaging.

SG-APSIC1091: Assessment of compliance to cleaning of computers by healthcare workers (HCWs) using adenosine triphosphate (ATP) measurement

Objectives: HCWs are recommended to wipe the computers with alcohol wipes before clinical use. Compliance assessment by direct observation is resource intensive. We used ATP measurement as a surrogate to assess the compliance to preutilization cleaning of computers. Methods: We conducted a pilot study to determine the median relative light unit (RLU) value reflective of preutilization cleaning of the computers. We identified values of <250, 250–500, and >500 RLU to reflect cleaned, probably cleaned, and not cleaned computers, respectively. Subsequently, we conducted a cross-sectional study of the computers in the inpatient wards in Tan Tock Seng Hospital and National Centre for Infectious Diseases. Using 3M Clean-Trace ATP swabs, we tested 5 computers in each ward: 2 computers on wheels, 2 from the nursing station, and 1 at the patients' room entrance. All analyses were conducted using STATA version 15 software. Results: Between October 4 and 10, 2021, we collected 219 samples from 219 computers. Among them, 44 (20.1%) were cleaned, 49 (22.4%) were probably cleaned, and 126 (57.5%) computers were not cleaned. Higher compliance to computer cleaning was observed in COVID-19 wards [85 ATP samples;cleaned, 37 (43.5%);probably cleaned, 26 (30.6%);not cleaned, 22 (25.9%)] compared with non–COVID-19 wards [134 ATP samples;cleaned, 7 (5.2%);probably cleaned, 23 (17.2%);not cleaned, 104 (77.6%)] (P < .01). No significant difference was observed in compliance with cleaning computers between the ICU [30 ATP samples;cleaned, 7 (23.3%);probably cleaned, 4 (13.3%);not cleaned, 19 (63.3%)] and general wards [189 ATP samples;cleaned, 37 (19.6%);probably cleaned, 45 (23.8%);not cleaned, 107 (56.6%)] (P = .47). Conclusions: ATP swab tests can be used as a surrogate marker to assess compliance to pre-utilization cleaning of computers. Enhanced awareness of environmental hygiene may explain the higher compliance to computer cleaning observed in COVID-19 wards.

SG-APSIC1097: The impact of COVID-19 on the incidence of carbapenem-resistant Enterobacterales (CRE) in Singapore: An interrupted time-series analysis

Objectives: Over the past 2 years, many infection prevention and control (IPC) resources have been diverted to manage the COVID-19 pandemic. Its impact on the incidence of antimicrobial-resistant organisms has not been adequately studied. We investigated the impact of the pandemic on the incidence of carbapenem-resistant Enterobacterales (CRE) in Singapore. Methods: We extracted data on unique CRE isolates (clinical and/or surveillance cultures) and patient days for 6 public hospitals in Singapore from the carbapenemase-producing Enterobacteriaceae (CaPES) study group database, and we calculated the monthly incidence of CRE (per 10,000 patient days). Interrupted time-series (ITS) analysis was conducted with the pre–COVID-19 period defined as before February 2020, and the COVID-19 period defined as after February 2020. Statistical analyses were performed using Stata version 15 software. Results: From January 2017 to March 2021, 6,770 CRE isolates and 9,126,704 patient days were documented. The trend in CRE monthly incidence increased significantly during the pre–COVID-19 period (0.060;95% CI, 0.033–0.094;P < .001) but decreased during the COVID-19 period (−0.183;95% CI, −0.390 to 0.023;P = .080) without stepwise change in the incidence (−1.496;95% CI, −3.477 to 0.485;P = .135). The trend in monthly incidence rate of CRE clinical cultures increased significantly during the pre–COVID-19 period (0.046;95% CI, 0.028–0.064;P < .001) and decreased significantly during COVID-19 period (−0.148;95% CI, −0.249 to −0.048;P = .048) with no stepwise change in the incidence (−0.063;95% CI, −0.803 to 0.677;P = .864). The trend in monthly incidence rate of CRE surveillance cultures decreased during the pre–COVID-19 period (−0.020;95% CI, −0.062 to 0.022;P = .341) and the COVID-19 period (−0.067;95% CI, −0.291to 0.158;P = .552) without stepwise change in the incidence (−1.327;95% CI, −3.535 to 0.881;P = .233). Conclusions: The rate of CRE in clinical cultures decreased during COVID-19 but not the rate in surveillance cultures. Further studies are warranted to study the impact of COVID-19 on CREs.(DUPLICATE DELETED)

Estimating the excess bed days and economic burden of healthcare-associated infections in Singapore public acute-care hospitals.

We estimated the annual bed days lost and economic burden of healthcare-associated infections to Singapore hospitals using Monte Carlo simulation. The mean (standard deviation) cost of a single healthcare-associated infection was S$1,809 (S$440) [or US$1,362 (US$331)]. This translated to annual lost bed days and economic burden of 55,978 (20,506) days and S$152.0 million (S$37.1 million) [or US$114.4 million (US$27.9 million)], respectively.

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.

Nanobiotics against antimicrobial resistance: harnessing the power of nanoscale materials and technologies.

Given the spasmodic increment in antimicrobial resistance (AMR), world is on the verge of "post-antibiotic era". It is anticipated that current SARS-CoV2 pandemic would worsen the situation in future, mainly due to the lack of new/next generation of antimicrobials. In this context, nanoscale materials with antimicrobial potential have a great promise to treat deadly pathogens. These functional materials are uniquely positioned to effectively interfere with the bacterial systems and augment biofilm penetration. Most importantly, the core substance, surface chemistry, shape, and size of nanomaterials define their efficacy while avoiding the development of AMR. Here, we review the mechanisms of AMR and emerging applications of nanoscale functional materials as an excellent substitute for conventional antibiotics. We discuss the potential, promises, challenges and prospects of nanobiotics to combat AMR.

Impact of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Vaccination and Pediatric Age on Delta Variant Household Transmission.

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.

Transmission modes of severe acute respiratory syndrome coronavirus 2 and implications for infection control: a review.

The complete picture regarding transmission modes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is unknown. This review summarises the available evidence on its transmission modes, our preliminary research findings and implications for infection control policy, and outlines future research directions. Environmental contamination has been reported in hospital settings occupied by infected patients, and is higher in the first week of illness. Transmission via environmental surfaces or fomites is likely, but decontamination protocols are effective in minimising this risk. The extent of airborne transmission is also unclear. While several studies have detected SARS-CoV-2 ribonucleic acid in air samples, none has isolated viable virus in culture. Transmission likely lies on a spectrum between droplet and airborne transmission, depending on the patient, disease and environmental factors. Singapore's current personal protective equipment and isolation protocols are sufficient to manage this risk.

Virtual Infection Prevention and Control in Low- and Middle-Income Countries.

COVID-19 brought new challenges and opportunities for infection prevention and control. Virtual infection prevention and control (VIPC), although nascent, is rapidly becoming a viable and necessary strategy for combatting the COVID-19 pandemic. Benefits of VIPC include extending the impact of globally scarce infectious disease providers and public health practitioners, allowing coordination between disparate professionals to more effectively combat infectious disease, and increasing access to and quality of healthcare. Although mainly applied in developed countries, VIPC may play its greatest role in low- and middle-income countries (LMICs) with fewer healthcare resources. We conducted a brief literature search of VIPC in LMICs and found that many studies describe solutions in developed countries or describe planned or theoretical solutions. Few studies describe actual VIPC implementation in LMICs, except for China. Literature from related fields, for example, virtual critical care, and from developed countries is more robust and provides a roadmap for future research on VIPC in LMICs. Further research into strategies and outcomes related to VIPC in LMICs is necessary.

Lack of viable severe acute respiratory coronavirus virus 2 (SARS-CoV-2) among PCR-positive air samples from hospital rooms and community isolation facilities.

BACKGROUND: Understanding the extent of aerosol-based transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is important for tailoring interventions for control of the coronavirus disease 2019 (COVID-19) pandemic. Multiple studies have reported the detection of SARS-CoV-2 nucleic acid in air samples, but only one study has successfully recovered viable virus, although it is limited by its small sample size. OBJECTIVE: We aimed to determine the extent of shedding of viable SARS-CoV-2 in respiratory aerosols from COVID-19 patients. METHODS: In this observational air sampling study, air samples from airborne-infection isolation rooms (AIIRs) and a community isolation facility (CIF) housing COVID-19 patients were collected using a water vapor condensation method into liquid collection media. Samples were tested for presence of SARS-CoV-2 nucleic acid using quantitative real-time polymerase chain reaction (qRT-PCR), and qRT-PCR-positive samples were tested for viability using viral culture. RESULTS: Samples from 6 (50%) of the 12 sampling cycles in hospital rooms were positive for SARS-CoV-2 RNA, including aerosols ranging from <1 µm to >4 µm in diameter. Of 9 samples from the CIF, 1 was positive via qRT-PCR. Viral RNA concentrations ranged from 179 to 2,738 ORF1ab gene copies per cubic meter of air. Virus cultures were negative after 4 blind passages. CONCLUSION: Although SARS-CoV-2 is readily captured in aerosols, virus culture remains challenging despite optimized sampling methodologies to preserve virus viability. Further studies on aerosol-based transmission and control of SARS-CoV-2 are needed.

Impact of Delta Variant and Vaccination on SARS-CoV-2 Secondary Attack Rate Among Household Close Contacts.

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.

Risk assessment of airborne COVID-19 exposure in social settings.

The COVID-19 pandemic has led to many countries oscillating between various states of lock-down as they seek to balance keeping the economy and essential services running and minimizing the risk of further transmission. Decisions are made about which activities to keep open across a range of social settings and venues guided only by ad hoc heuristics regarding social distancing and personal hygiene. Hence, we propose the dual use of computational fluid dynamic simulations and surrogate aerosol measurements for location-specific assessment of risk of infection across different real-world settings. We propose a 3-tiered risk assessment scheme to facilitate classification of scenarios into risk levels based on simulations and experiments. Threshold values of <54 and >840 viral copies and <5% and >40% of original aerosol concentration are chosen to stratify low, medium, and high risk. This can help prioritize allowable activities and guide implementation of phased lockdowns or re-opening. Using a public bus in Singapore as a case study, we evaluate the relative risk of infection across scenarios such as different activities and passenger positions and demonstrate the effectiveness of our risk assessment methodology as a simple and easily interpretable framework. For example, this study revealed that the bus's air-conditioning greatly influences dispersion and increases the risk of certain seats and that talking can result in similar relative risk to coughing for passengers around an infected person. Both numerical and experimental approaches show similar relative risk levels with a Spearman's correlation coefficient of 0.74 despite differing observables, demonstrating applicability of this risk assessment methodology to other scenarios.