Timing and Predictors of Loss of Infectivity Among Healthcare Workers With Mild Primary and Recurrent COVID-19: A Prospective Observational Cohort Study

BACKGROUND

There is a need to understand the duration of infectivity of primary and recurrent coronavirus disease 2019 (COVID-19) and identify predictors of loss of infectivity.

METHODS

Prospective observational cohort study with serial viral culture, rapid antigen detection test (RADT) and reverse transcription polymerase chain reaction (RT-PCR) on nasopharyngeal specimens of healthcare workers with COVID-19. The primary outcome was viral culture positivity as indicative of infectivity. Predictors of loss of infectivity were determined using multivariate regression model. The performance of the US Centers for Disease Control and Prevention (CDC) criteria (fever resolution, symptom improvement, and negative RADT) to predict loss of infectivity was also investigated.

RESULTS

In total, 121 participants (91 female [79.3%]; average age, 40 years) were enrolled. Most (n = 107, 88.4%) had received ≥3 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine doses, and 20 (16.5%) had COVID-19 previously. Viral culture positivity decreased from 71.9% (87/121) on day 5 of infection to 18.2% (22/121) on day 10. Participants with recurrent COVID-19 had a lower likelihood of infectivity than those with primary COVID-19 at each follow-up (day 5 odds ratio [OR], 0.14; P < .001]; day 7 OR, 0.04; P = .003]) and were all non-infective by day 10 (P = .02). Independent predictors of infectivity included prior COVID-19 (adjusted OR [aOR] on day 5, 0.005; P = .003), an RT-PCR cycle threshold [Ct] value <23 (aOR on day 5, 22.75; P < .001) but not symptom improvement or RADT result.The CDC criteria would identify 36% (24/67) of all non-infectious individuals on day 7. However, 17% (5/29) of those meeting all the criteria had a positive viral culture.

CONCLUSIONS

Infectivity of recurrent COVID-19 is shorter than primary infections. Loss of infectivity algorithms could be optimized.

Medical Masks Versus N95 Respirators for Preventing COVID-19 Among Health Care Workers : A Randomized Trial

BACKGROUND

It is uncertain if medical masks offer similar protection against COVID-19 compared with N95 respirators.

OBJECTIVE

To determine whether medical masks are noninferior to N95 respirators to prevent COVID-19 in health care workers providing routine care.

DESIGN

Multicenter, randomized, noninferiority trial. (ClinicalTrials.gov: NCT04296643).

SETTING

29 health care facilities in Canada, Israel, Pakistan, and Egypt from 4 May 2020 to 29 March 2022.

PARTICIPANTS

1009 health care workers who provided direct care to patients with suspected or confirmed COVID-19.

INTERVENTION

Use of medical masks versus fit-tested N95 respirators for 10 weeks, plus universal masking, which was the policy implemented at each site.

MEASUREMENTS

The primary outcome was confirmed COVID-19 on reverse transcriptase polymerase chain reaction (RT-PCR) test.

RESULTS

In the intention-to-treat analysis, RT-PCR-confirmed COVID-19 occurred in 52 of 497 (10.46%) participants in the medical mask group versus 47 of 507 (9.27%) in the N95 respirator group (hazard ratio [HR], 1.14 [95% CI, 0.77 to 1.69]). An unplanned subgroup analysis by country found that in the medical mask group versus the N95 respirator group RT-PCR-confirmed COVID-19 occurred in 8 of 131 (6.11%) versus 3 of 135 (2.22%) in Canada (HR, 2.83 [CI, 0.75 to 10.72]), 6 of 17 (35.29%) versus 4 of 17 (23.53%) in Israel (HR, 1.54 [CI, 0.43 to 5.49]), 3 of 92 (3.26%) versus 2 of 94 (2.13%) in Pakistan (HR, 1.50 [CI, 0.25 to 8.98]), and 35 of 257 (13.62%) versus 38 of 261 (14.56%) in Egypt (HR, 0.95 [CI, 0.60 to 1.50]). There were 47 (10.8%) adverse events related to the intervention reported in the medical mask group and 59 (13.6%) in the N95 respirator group.

LIMITATION

Potential acquisition of SARS-CoV-2 through household and community exposure, heterogeneity between countries, uncertainty in the estimates of effect, differences in self-reported adherence, differences in baseline antibodies, and between-country differences in circulating variants and vaccination.

CONCLUSION

Among health care workers who provided routine care to patients with COVID-19, the overall estimates rule out a doubling in hazard of RT-PCR-confirmed COVID-19 for medical masks when compared with HRs of RT-PCR-confirmed COVID-19 for N95 respirators. The subgroup results varied by country, and the overall estimates may not be applicable to individual countries because of treatment effect heterogeneity.

PRIMARY FUNDING SOURCE

Canadian Institutes of Health Research, World Health Organization, and Juravinski Research Institute.

Low-dose trimethoprim-sulfamethoxazole for the treatment of Pneumocystis jirovecii pneumonia (LOW-TMP): protocol for a phase III randomised, placebo-controlled, dose-comparison trial

INTRODUCTION

Pneumocystis jirovecii pneumonia (PJP) is an opportunistic infection of immunocompromised hosts with significant morbidity and mortality. The current standard of care, trimethoprim-sulfamethoxazole (TMP-SMX) at a dose of 15-20 mg/kg/day, is associated with serious adverse drug events (ADE) in 20%-60% of patients. ADEs include hypersensitivity reactions, drug-induced liver injury, cytopenias and renal failure, all of which can be treatment limiting. In a recent meta-analysis of observational studies, reduced dose TMP-SMX for the treatment of PJP was associated with fewer ADEs, without increased mortality.

METHODS AND ANALYSIS

A phase III randomised, placebo-controlled, trial to directly compare the efficacy and safety of low-dose TMP-SMX (10 mg/kg/day of TMP) with the standard of care (15 mg/kg/day of TMP) among patients with PJP, for a composite primary outcome of change of treatment, new mechanical ventilation, or death. The trial will be undertaken at 16 Canadian hospitals. Data will be analysed as intention to treat. Primary and secondary outcomes will be compared using logistic regression adjusting for stratification and presented with 95% CI.

ETHICS AND DISSEMINATION

This study has been conditionally approved by the McGill University Health Centre; Ethics approval will be obtained from all participating centres. Results will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT04851015.

415. A Whole Genome Sequencing Analysis of a Multi-unit Long-term Care Facility COVID-19 Outbreak

Background

The coronavirus disease (COVID-19) pandemic has affected residents in long-term care facilities (LTCF) significantly. Understanding transmission dynamics in this setting is crucial to control the spread of COVID-19 in this population. Using whole genome sequencing (WGS) of SARS-CoV-2, we aimed to delineate the points of introduction and transmission pathways in a large LTCF in Quebec, Canada.

Methods

Between 2020-10-28 and 2021-01-09, COVID-19 cases occurred in 102 residents and 111 HCW at a 387-bed LTCF; cases were distributed in 11 units on 6 floors. As part of outbreak analysis, SARS-CoV-2 isolates underwent WGS using the Oxford Nanopore Minion and the Artic V3 protocol. Lineage attribution and sequence types (ST, within 3 mutations) were assigned based on Pangolin classification and variant analysis. Epidemiologic data including date of positive PCR test, resident room number and HCW work location were collected. Self-reported high-risk exposures were collected by HCW questionnaire via phone interview after consent. Cases and their ST, geo-temporal relations and HCW-reported exposures were examined via network plots and geography-based epidemic curves to infer points of introduction and paths of transmission.

Results

Of 170 isolates available from 100/102 residents and 70/111 HCW, 130 (76.4%) were successfully sequenced. Phylogenetic analysis revealed 7 separate introductions to the LTCF. Grouping of ST by units was observed, with temporal appearance of ST supporting HCW introduction in 7/11 units. Proportion of phone interview completion was low at 35% (26/70). Few HCW recalled specific high-risk exposures. Recalled exposures supported by genetic linkage revealed potential between-unit introductions from HCW-to-HCW transmission at work and outside the workplace (e.g. carpooling). On one unit, a wandering resident was identified as a likely source of transmission to other residents (Figure 1).

Network plot of cases clustered by geographic unit, colour-coded by sequence type. Circles represent residents; addition signs represent healthcare workers. Blue lines represent identified high-risk exposures. Node labels represent floor and unit identifiers; 2 units per floor.

Conclusion

We demonstrate the complex genomic epidemiology of a multi-unit LTCF outbreak, putting into evidence the importance of a multi-faceted approach to limit transmission. This analysis highlights the utility of using WGS to uncover unsuspected transmission routes, such as HCW contact outside work, which can prompt new infection control measures.

Disclosures

All Authors: No reported disclosures

Covid-19 vaccine acceptance, hesitancy, and refusal among Canadian healthcare workers: A multicenter survey

BACKGROUND

Determinants of COVID-19 vaccine acceptance among healthcare workers (HCW) remains poorly understood. We assessed HCWs' willingness to be vaccinated and reasons underlying hesitancy.

METHODS

Cross-sectional survey across 17 healthcare institutions. HCWs eligible for vaccination (Pfizer-BioNTech mRNA) in December 2020 were invited to receive immunization. Multivariate logistic regression was performed to identify predictors of acceptance. Reasons for refusal among those who never intended to be vaccinated (ie, firm refusers) and those who preferred delaying vaccination (ie, vaccine hesitants) were assessed.

RESULTS

Among 2,761 respondents (72% female, average age, 44), 2,233 (80.9%) accepted the vaccine. Physicians, environmental services workers and healthcare managers were more likely to accept vaccination compared to nurses. Male sex, age over 50, rehabilitation center workers, and occupational COVID-19 exposure were independently associated with vaccine acceptance by multivariate analysis. Factors for refusal included vaccine novelty, wanting others to receive it first, and insufficient time for decision-making. Among those who declined, 74% reported they may accept future vaccination. Vaccine firm refusers were more likely than vaccine hesitants to distrust pharmaceutical companies and to prefer developing a natural immunity by getting COVID-19.

CONCLUSIONS

Vaccine hesitancy exists among HCWs. Our findings provide useful information to plan future interventions and improve acceptance.

Switching from expectorated to induced sputum cultures for tuberculosis diagnosis reduces cost without increasing risk

Active pulmonary tuberculosis testing with 3 expectorated sputa can increase isolation days and expenditures compared with 1 induced sputum. Six-month retrospective and prospective chart reviews were conducted, and a screening algorithm was phased into 2 hospital sites. With induced sputum testing, isolation decreased from 7 to 4 days (interquartile range, 4-3, P = .0135), and there was a cost savings of $7,275 per case, with no added harm.

Direct monitoring of breast and endometrial cancer cell epigenetic response to DNA methyltransferase and histone deacetylase inhibitors

DNA methylation and histone deacetylation are key epigenetic processes involved in normal cellular function and tumorigenesis. Therapeutic strategies based on DNA methyltransferase (DNMT) and histone deacetylase (HDAC) inhibitors are currently in use and under development for the treatment of cancers. Genome-wide DNA methylation profiling has been proposed for use in disease diagnosis, and histone modification profiling for disease stratification will follow suit. However, whether epigenome sequencing technologies will be feasible for rapid clinic diagnosis and patient treatment monitoring remains to be seen, and alternative detection technologies will almost certainly be needed. Here we used electrochemical impedance spectroscopy (EIS) employing a graphene-based screen-printed electrode system to directly measure global DNA methylation and histone H3 acetylation to compare non-cancer and breast cancer cell lines. We demonstrated that whilst global methylation was not useful as a differential marker in the cellular systems tested, histone H3 acetylation was effective at higher chromatin levels. Using breast and endometrial cancer cell models, EIS was then used to monitor cellular responses to the DNMT and HDAC inhibitors 5-Aza-2'-deoxycytidine and suberoylanilide hydroxamic acid in vitro, and proved very effective at detecting global cellular responses to either treatment, indicating that this approach could be useful in following treatment response to epigenetic drugs. Moreover, this work reports the first combined analysis of two epigenetic markers using a unified graphene-based biosensor platform, demonstrating the potential for multiplex analysis of both methylation and acetylation on the same sample.

The Efficacy of Computed Tomography-Guided Percutaneous Spine Biopsies in Determining a Causative Organism in Cases of Suspected Infection: A Systematic Review

Purpose

In suspected spondylodiscitis and vertebral osteomyelitis, computed tomography (CT)-guided biopsies are often performed to determine a causative organism and guide antimicrobial therapy. The aim of this study is to determine the diagnostic culture yield of CT-guided biopsies performed in cases of suspected spinal infections.

Methods

A literature search of PubMed and MEDLINE up to April 2017 was performed for keywords “CT guided vertebral biopsy infection,” “CT-guided spine biopsy infection,” “CT guided spine biopsy yield,” and “CT guided vertebral biopsy yield.” Inclusion criteria primarily consisted of studies exclusively using CT-guided biopsies in cases of suspected infectious lesions only. After study selection, published articles were analysed to determine diagnostic culture yield. Descriptive statistics were applied.

Results

220 search results were screened; 11 met our inclusion criteria and were reviewed. In total, 647 biopsies of suspected infectious spinal lesions were performed. Positive cultures were obtained in 241 cases. Upon excluding one paper's skewed results, the net pooled results culture yield was 33%. Several cultures grew multiple organisms, leading to a total of 244 species identified. Most common isolated organisms include S taphylococcus aureus (n = 83), coagulase-negative S taphylococcus (n = 45), and Mycobacteria (n = 38).

Conclusions

The diagnostic culture yield of CT-guided biopsies in cases of suspected spinal infection is 33%. In the majority of cases, a causative organism is not identified. This suggests that improvements can be made in biopsy technique and specimen transfer to optimize culture yield and increase the clinical value of the procedure.

The effect of sex and handedness on white matter anisotropy: a diffusion tensor magnetic resonance imaging study

Diffusion tensor magnetic resonance imaging provides a way of assessing the asymmetry of white matter (WM) connectivity, the degree of anisotropic diffusion within a given voxel being a marker of coherently bundled myelinated fibers. Voxel-based statistical analysis was performed on fractional anisotropy (FA) images of 42 right- and 40 left-handers, to assess differences in underlying WM anisotropy and FA asymmetry across the whole brain. Right-handers show greater anisotropy than left-handers in the uncinate fasciculus (UF) within the limbic lobe, and WM underlying prefrontal cortex, medial and inferior frontal gyri. Significantly greater leftward FA asymmetry in cerebellum posterior lobe is seen in left- than right-handers, and males show significantly greater rightward (right-greater-than-left) FA asymmetry in regions of middle occipital lobe, medial temporal gyrus, and a region of the superior longitudinal fasciculus underlying the supramarginal gyrus. Leftward (left-greater-than-right) anisotropy is found in regions of the arcuate fasciculus (AF), UF, and WM underlying pars triangularis in both handedness groups, with right-handers alone showing additional leftward FA asymmetry along the length of the superior temporal gyrus. Overall results indicate that although both handedness groups show anisotropy in similar WM regions, greater anisotropy is observed in right-handers compared with left-handers. The largest differences in FA asymmetry are found between males and females, suggesting a greater effect of sex than handedness on FA asymmetry.

Retrospective, observational data collection of the treatment of phenylketonuria in the UK, and associated clinical and health outcomes

OBJECTIVE

To determine the percentage of phenylketonuria (PKU) subjects using current treatment strategies whose phenylalanine (Phe) concentrations diverge from the UK target guidelines for PKU.

RESEARCH DESIGN AND METHODS

This retrospective, observational, chart review was conducted between 2004 and 2008 at three specialist PKU treatment centres in the UK, and included 125 eligible subjects: 20 adults (18+ years, with ≥4 Phe concentrations measured per year) and 105 children (up to age 17, with ≥6 Phe concentrations measured per year).

RESULTS

The mean percentage of subjects with at least 70% of Phe concentrations within the target range for 0-5-year olds, 6-10 year olds and 11-17 year olds was similar across the period 2004-2008 (57.0%, 56.5% and 57.1%, respectively) and lower (39.4%) in the 18+ year age group. For all ages, across the period the mean was 54.4%. Further analysis of the adult population showed that some subjects were very good at complying with treatment and reporting Phe concentrations. Overall, the percentage of 100% compliance was 15.7% in females and 13.7% in males. The mean duration that subjects were 'out of range' of target Phe concentrations over the study period was approximately 1 year and 3 months and the mean duration for 'significantly out of range' values was approximately 9 months. The most common type of contact made with subjects was by telephone, with a mean number of 16 calls per subject per year.

CONCLUSION

The results support current literature showing that a proportion of subjects with PKU, in particular older subjects, are not fully compliant with their treatment and subsequently have Phe concentrations that depart from national recommendations. However, definitive conclusions may not be drawn due to the retrospective nature of the study and the small number of observed subjects.

Compulsory averaging of crowded orientation signals in human vision

A shape can be more difficult to identify when other shapes are near it. For example, when several grating patches are viewed parafoveally, observers are unable to report the orientation of the central patch. This phenomenon, known as 'crowding,' has historically been confused with lateral masking, in which one stimulus attenuates signals generated by another stimulus. Here we show that despite their inability to report the orientation of an individual patch, observers can reliably estimate the average orientation, demonstrating that the local orientation signals are combined rather than lost. Our results imply that crowding is distinct from ordinary masking, and is perhaps related to texture perception. Under crowded conditions, the orientation signals in primary visual cortex are pooled before they reach consciousness.

Protection against group B meningococcal disease. I. Comparison of group-specific and type-specific protection in the chick embryo model

Protection against group B meningococcal infection was examined using the chick embryo. 12-day-old embryos were challenged intravenously with various meningococcal strains. The chick embryo has an active reticuloendothelial system but lacks functional complement. In this model we found that protection against group B infection was primarily group specific. The group B polysaccharide antibody is an effective opsonin, but is a very poor bactericidal antibody. In contrast, the serotype antibody was bactericidal but only slightly protective in the chick embryo where protection is primarily phagocytic in nature. The group-specific and type-specific antibodies are strongly synergistic. Minute amounts of group B polysaccharide antibody caused a very significant increase in the protective effects of the serotype antibody.