Clinical outcomes associated with SARS-CoV-2 Omicron (B.1.1.529) variant and BA.1/BA.1.1 or BA.2 subvariant infection in southern California

Sequence Matters: Primary COVID-19 Vaccination after Infection Elicits Similar Anti-spike Antibody Levels, but Stronger Antibody Dependent Cell-mediated Cytotoxicity than Breakthrough Infection

Infection before primary vaccination (herein termed "hybrid immunity") engenders robust humoral immunity and broad Ab-dependent cell-mediated cytotoxicity (ADCC) across SARS-CoV-2 variants. We measured and compared plasma IgG and IgA against Wuhan-Hu-1 and Omicron (B.1.1.529) full-length spike (FLS) and receptor binding domain after three mRNA vaccines encoding Wuhan-Hu-1 spike (S) and after Omicron breakthrough infection. We also measured IgG binding to Wuhan-Hu-1 and Omicron S1, Wuhan-Hu-1 S2 and Wuhan-Hu-1 and Omicron cell-based S. We compared ADCC using human embryonic lung fibroblast (MRC-5) cells expressing Wuhan-Hu-1 or Omicron S. The effect of Omicron breakthrough infection on IgG anti-Wuhan-Hu-1 and Omicron FLS avidity was also considered. Despite Omicron breakthrough infection increasing IgG and IgA against FLS and receptor binding domain to levels similar to those seen with hybrid immunity, there was no boost to ADCC. Preferential recognition of Wuhan-Hu-1 persisted following Omicron breakthrough infection, which increased IgG avidity against Wuhan-Hu-1 FLS. Despite similar total anti-FLS IgG levels following breakthrough infection, 4-fold higher plasma concentrations were required to elicit ADCC comparable to that elicited by hybrid immunity. The greater capacity for hybrid immunity to elicit ADCC was associated with a differential IgG reactivity pattern against S1, S2, and linear determinants throughout FLS. Immunity against SARS-CoV-2 following Omicron breakthrough infection manifests significantly less ADCC capacity than hybrid immunity. Thus, the sequence of antigenic exposure by infection versus vaccination and other factors such as severity of infection affect antiviral functions of humoral immunity in the absence of overt quantitative differences in the humoral response.

Immune escape and attenuated severity associated with the SARS-CoV-2 BA.2.86/JN.1 lineage

The SARS-CoV-2 BA.2.86 lineage, and its sublineage JN.1 in particular, achieved widespread transmission in the US during winter 2023-24. However, this surge in infections was not accompanied by COVID-19 hospitalizations and mortality commensurate with prior waves. To understand shifts in COVID-19 epidemiology associated with JN.1 emergence, we compared characteristics and clinical outcomes of time-matched cases infected with BA.2.86 lineages (predominantly representing JN.1) versus co-circulating XBB-derived lineages in December, 2023 and January, 2024. Cases infected with BA.2.86 lineages received greater numbers of COVID-19 vaccine doses, including XBB.1.5-targeted boosters, in comparison to cases infected with XBB-derived lineages. Additionally, cases infected with BA.2.86 lineages experienced greater numbers of documented prior SARS-CoV-2 infections. Cases infected with BA.2.86 lineages also experienced lower risk of progression to severe clinical outcomes requiring emergency department consultations or hospital admission. Sensitivity analyses suggested under-ascertainment of prior infections could not explain this apparent attenuation of severity. Our findings implicate escape from immunity acquired from prior vaccination or infection in the emergence of the JN.1 lineage and suggest infections with this lineage are less likely to experience clinically-severe disease. Monitoring of immune escape and clinical severity in emerging SARS-CoV-2 variants remains a priority to inform responses.

The epidemiology and phylogenetic trends of Omicron subvariants from BA.5 to XBB.1 in Taiwan

BACKGROUND

Omicron, a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant, entered Taiwan at the end of 2021. The Taiwanese government ended its "zero-COVID" policy in March 2022. Multiple coronavirus disease 2019 (COVID-19) outbreaks began in April 2022. We monitored the replacement of Omicron subvariants after BA.1/BA.2 and analyzed their correlation with COVID-19 outbreaks.

METHODS

We collected SARS-CoV-2 real-time qRTPCR-positive nasopharyngeal swabs from Kaohsiung Medical University Hospital (KMUH), Kaohsiung City, Taiwan, and performed sequencing for specimens exhibiting a cytopathic effect in Vero E6 cells to determine their clades and lineages. We analyzed the medical records of COVID-19 patients and identified hospitalization risk factor(s). We retrieved SARS-CoV-2 sequences identified in Taiwan from GISAID and analyzed their correlation with COVID-19 data from the Taiwan Centers for Disease Control.

RESULTS

We analyzed the phylogenesis of KMUH-47 to KMUH-104 (SARS-CoV-2 isolates identified herein) and all of the Omicron subvariants from BA.5 to XBB.1 (n = 1930). Age and comorbidities were hospitalization risk factors. Men generally exhibited a greater fatality rate than women. COVID-19-related deaths predominantly occurred in individuals over 70 years old. The COVID-19-related case fatality rate increased as nucleotide (NT) and amino acid (AA) substitutions increased. The number of COVID-19-related cases and deaths progressively decreased with each outbreak between August 2022 and October 2023.

CONCLUSION

Hospitalization was associated with age and the presence of comorbidities. COVID-19-related fatality was linked to sex, age, and the accumulation of NT and AA substitutions in emerging Omicron subvariants.

Evaluation of risk prediction scores for adults hospitalized with COVID-19 in a highly-vaccinated population, Aotearoa New Zealand 2022

Objectives

COVID-19 severity prediction scores need further validation due to evolving COVID-19 illness. We evaluated existing COVID-19 risk prediction scores in Aotearoa New Zealand, including for Māori and Pacific peoples who have been inequitably affected by COVID-19.

Methods

We conducted a multicenter retrospective cohort study in adults hospitalized with COVID-19 from January to May 2022, including all Māori and Pacific patients, and every second non-Māori, non-Pacific (NMNP) patient to achieve equal analytic power by ethnic grouping. We assessed the accuracy of existing severity scores (4C Mortality, CURB-65, PRIEST, and VACO) to predict death in the hospital or within 28 days.

Results

Of 2319 patients, 582 (25.1%) identified as Māori, 914 (39.4%) as Pacific, and 862 (37.2%) as NMNP. There were 146 (6.3%, 95% confidence interval 5.4-7.4%) deaths, with a predicted probability of death higher than observed mortality for VACO (10.4%), modified PRIEST (15.1%) and 4C mortality (15.5%) scores, but lower for CURB-65 (4.5%). C-statistics (95% CI) of severity scores were: 4C mortality: Māori 0.82 (0.75, 0.88), Pacific 0.87 (0.83, 0.90), NMNP 0.90 (0.86, 0.93); CURB-65: Māori 0.83 (0.69, 0.92), Pacific 0.87 (0.82, 0.91), NMNP 0.86 (0.80, 0.91); modified PRIEST: Māori 0.85 (0.79, 0.90), Pacific 0.81 (0.76, 0.86), NMNP 0.83 (0.78, 0.87); and VACO: Māori 0.79 (0.75, 0.83), Pacific 0.71 (0.58, 0.82), NMNP 0.78 (0.73, 0.83).

Conclusions

Following re-calibration, existing risk prediction scores accurately predicted mortality.

Evaluating the Usefulness of Population-Wide COVID-19 Testing in the Omicron Era: Insights from a German Model

BACKGROUND

The Omicron variant of SARS-CoV-2, which has become dominant worldwide since late 2021, presents a unique challenge due to its high rate of asymptomatic transmission. This study evaluates the efficacy and value of population-wide testing, including self-testing, in the context of COVID-19, particularly under the Omicron variant, using data from Germany.

METHODS

A decision-analytical model and secondary data was used for assessing the impact of systematic screening and testing for COVID-19. Various scenarios were taken into consideration including seasonal patterns of COVID-19 transmission and the potential for annual waves. The model assessed the clinical benefits of testing against the backdrop of vaccine effectiveness, transmission rates, and the potential to prevent severe clinical events, including death, ICU admission, and long COVID syndrome.

RESULTS

The study found that the value of mass testing and self-testing for private use was highly contingent on the transmission rate and the scenario of COVID-19 waves (seasonal vs. continuous). For winter waves, a very high incidence rate was required to justify testing, while for continuous waves, testing could be valuable for those in contact with individuals in their last decade of life. The analysis highlighted the limitations of mass testing when community transmission rates were low and the potential value of testing in high-risk contacts or amidst new outbreaks.

DISCUSSION

The findings suggest that the resumption of testing during winter waves is unlikely to provide significant clinical benefits given the current understanding of Omicron's transmission and immunity waning. This study underscores the need for a nuanced approach to COVID-19 testing policies, considering both the epidemiological context and the practical implications of testing strategies.

The effect of early versus late remdesivir treatment in hospitalized mild to moderate COVID-19 patients in the Omicron era: A retrospective study

Although real-world studies have found that remdesivir is effective in preventing poor prognosis, more information is needed on the optimal timing of remdesivir administration in high-risk coronavirus disease 2019 (COVID-19) patients in the Omicron era. From February 2022 to January 2023, a single-center retrospective study was performed in Korea. We compared the clinical characteristics and treatment outcomes between early (remdesivir treatment within 0-3 days from symptom onset) and late (≥ 4 days from symptom onset) treatment groups of patients who received remdesivir monotherapy. Of 284 patients, 225 were classified into the early treatment group and 59 were classified into the late treatment group. The early treatment group had a lower rate of 28-day progression to severe disease than the late treatment group (1.4% vs 7.4%, P = .03). Delaying remdesivir treatment ≥ 4 days from symptom onset (adjusted odds ratio [aOR], 6.17; 95% CI, 1.18-32.44; P = .03) and Charlson comorbidity index ≥ 3 (aOR, 9.62; 95% CI, 1.65-56.10; P = .01) were independent risk factors for 28-day progression to severe disease. Our results suggest that early administration of remdesivir could be associated with better prognosis in COVID-19 patients with the Omicron variant, and within 3 days from symptom onset seems to be the appropriate timing.

Infectious disease surveillance needs for the United States: lessons from Covid-19

The COVID-19 pandemic has highlighted the need to upgrade systems for infectious disease surveillance and forecasting and modeling of the spread of infection, both of which inform evidence-based public health guidance and policies. Here, we discuss requirements for an effective surveillance system to support decision making during a pandemic, drawing on the lessons of COVID-19 in the U.S., while looking to jurisdictions in the U.S. and beyond to learn lessons about the value of specific data types. In this report, we define the range of decisions for which surveillance data are required, the data elements needed to inform these decisions and to calibrate inputs and outputs of transmission-dynamic models, and the types of data needed to inform decisions by state, territorial, local, and tribal health authorities. We define actions needed to ensure that such data will be available and consider the contribution of such efforts to improving health equity.

The role of hematological parameters in asymptomatic and non-severe cases of Omicron variant infection

BACKGROUND

Omicron variants are currently the predominant circulating lineage worldwide and most cases are mild or asymptomatic. The Omicron variant is characterized by high transmissibility and immune evasion. Early identification of Omicron cases in clinical settings is crucial for controlling its spread. Previous studies have indicated that changes in hematological parameters can be used to predict the severity of coronavirus disease 2019 (COVID-19). However, the role of hematological parameters in non-severe and asymptomatic cases remains unknown. This study aimed to investigate the role of hematological parameters in non-severe and asymptomatic Omicron variant infections.

METHODS

Hematological parameters and results were analyzed and compared in symptomatic (n = 356) and asymptomatic (n = 171) groups respectively, and between these two groups with positive COVID-19 tests. The utility of hematological parameters for predicting positive COVID-19 tests was analyzed using receiver operating characteristic curves.

RESULTS

Individuals with non-severe cases exhibited decreased levels of platelets, lymphocytes, eosinophils, basophils, lymphocytes (%), eosinophils (%), and basophils (%), while exhibiting elevated counts of monocytes, neutrophils (%), monocytes (%), neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio (PLR), and C-reactive protein (CRP) when compared to suspected cases or asymptomatic carriers. In asymptomatic patients, positive carriers had lower leukocyte, neutrophil, and lymphocyte counts but higher monocyte, monocyte (%), PLR, and CRP levels than negative carriers. Basophil counts combined with lymphocytes or the PLR demonstrated a more significant predictive value in screening non-severe cases earlier compared to other parameters. The combined assessment of the monocyte (%) and the PLR had the highest area under the curve for diagnosing asymptomatic carriers.

CONCLUSIONS

Circulating basophils, alone or in combination with other hematological parameters, may be used as efficient biomarkers for early screening of non-severe Omicron cases.

Enhanced Surface Accessibility of SARS-CoV-2 Omicron Spike Protein Due to an Altered Glycosylation Profile

SARS-CoV-2 spike (S) proteins undergo extensive glycosylation, aiding in proper folding, enhancing stability, and evading host immune surveillance. In this study, we used mass spectrometric analysis to elucidate the N-glycosylation characteristics and disulfide bonding of recombinant spike proteins derived from the SARS-CoV-2 Omicron variant (B.1.1.529) in comparison with the D614G spike variant. Furthermore, we conducted microsecond-long molecular dynamics simulations on spike proteins to resolve how the different N-glycans impact spike conformational sampling in the two variants. Our findings reveal that the Omicron spike protein maintains an overall resemblance to the D614G spike variant in terms of site-specific glycan processing and disulfide bond formation. Nonetheless, alterations in glycans were observed at certain N-glycosylation sites. These changes, in synergy with mutations within the Omicron spike protein, result in increased surface accessibility of the macromolecule, including the ectodomain, receptor-binding domain, and N-terminal domain. Additionally, mutagenesis and pull-down assays reveal the role of glycosylation of a specific sequon (N149); furthermore, the correlation of MD simulation and HDX-MS identified several high-dynamic areas of the spike proteins. These insights contribute to our understanding of the interplay between structure and function, thereby advancing effective vaccination and therapeutic strategies.

Prescribing Patterns of Nonrecommended Medications for Children With Acute COVID-19

OBJECTIVE

Repurposed medications for acute coronavirus disease 2019 (COVID-19) continued to be prescribed after results from rigorous studies and national guidelines discouraged use. We aimed to describe prescribing rates of nonrecommended medications for acute COVID-19 in children, associations with demographic factors, and provider type and specialty.

METHODS

In this retrospective cohort of children <18 years in a large United States all-payer claims database, we identified prescriptions within 2 weeks of an acute COVID-19 diagnosis. We calculated prescription rate, performed multivariable logistic regression to identify risk factors, and described prescriber type and specialty during nonrecommended periods defined by national guidelines.

RESULTS

We identified 3 082 626 COVID-19 diagnoses in 2 949 118 children between March 7, 2020 and December 31, 2022. Hydroxychloroquine (HCQ) and ivermectin were prescribed in 0.03% and 0.14% of COVID-19 cases, respectively, during nonrecommended periods (after September 12, 2020 for HCQ and February 5, 2021 for ivermectin) with considerable variation by state. Prescription rates were 4 times the national average in Arkansas (HCQ) and Oklahoma (ivermectin). Older age, nonpublic insurance, and emergency department or urgent care visit were associated with increased risk of either prescription. Additionally, residence in nonurban and low-income areas was associated with ivermectin prescription. General practitioners had the highest rates of prescribing.

CONCLUSIONS

Although nonrecommended medication prescription rates were low, the overall COVID-19 burden translated into high numbers of ineffective and potentially harmful prescriptions. Understanding overuse patterns can help mitigate downstream consequences of misinformation. Reaching providers and parents with clear evidence-based recommendations is crucial to children's health.

Projecting the future impact of emerging SARS-CoV-2 variants under uncertainty: Modeling the initial Omicron outbreak

Over the past several years, the emergence of novel SARS-CoV-2 variants has led to multiple waves of increased COVID-19 incidence. When the Omicron variant emerged, there was considerable concern about its potential impact in the winter of 2021-2022 due to its increased fitness. However, there was also considerable uncertainty regarding its likely impact due to questions about its relative transmissibility, severity, and degree of immune escape. We sought to evaluate the ability of an agent-based model to forecast incidence in the context of this emerging pathogen variant. To project COVID-19 cases and deaths in Indiana, we calibrated our model to COVID-19 hospitalizations, deaths, and test-positivity rates through November 2021, and then projected COVID-19 incidence through April 2022 under four different scenarios that covered the plausible ranges of Omicron's severity, transmissibility, and degree of immune escape. Our initial projections from December 2021 through March 2022 indicated that under a pessimistic scenario with high disease severity, the peak in weekly COVID-19 deaths in Indiana would be larger than the previous peak in December 2020. However, retrospective analyses indicate that Omicron's severity was closer to the optimistic scenario, and even though cases and hospitalizations reached a new peak, fewer deaths occurred than during the previous peak. According to our results, Omicron's rapid spread was consistent with a combination of higher transmissibility and immune escape relative to earlier variants. Our updated projections starting in January 2022 accurately predicted that cases would peak in mid-January and decline rapidly over the next several months. The performance of our projections shows that following the emergence of a new pathogen variant, models can help quantify the potential range of outbreak magnitudes and trajectories. Agent-based models are particularly useful in these scenarios because they can efficiently track individual vaccination and infection histories with multiple variants with varying degrees of cross-protection.

Clinical characteristics and risk factors in patients with SARS-CoV-2 Omicron variant infection complicated with cardiovascular diseases

Objective

To investigate the clinical characteristics and risk factors of patients with SARS-CoV-2 Omicron variant infection complicated with cardiovascular diseases.

Methods

A retrospective analysis of general clinical data was conducted on patients with SARS-CoV-2 omicron infection complicated with hypertension, coronary heart disease, and heart failure admitted to one hospital in Guangdong Province from December 1, 2022, to February 28, 2023. Clinical symptoms, laboratory tests, imaging examinations, treatment, and clinical outcomes were collected. Multivariate logistic regression analysis was used to analyze the risk factors for mortality in patients with SARS-CoV-2 Omicron variant infection complicated with cardiovascular diseases. ROC curves were drawn to evaluate the predictive value of CRP, D-dimer, and CK-MB in predicting the risk of death.

Results

A total of 364 confirmed cases were included, divided into the asymptomatic group, mild to moderate group, and severe to critically ill group based on the symptoms of COVID-19. There were 216 males (59.34%) and 148 females (40.66%), with a median age of 75 years. The differences between the three groups in terms of sex and age were statistically significant (p < 0.05). The top three underlying diseases were hypertension (288 cases, 79.12%), coronary heart disease (100 cases, 27.47%), and diabetes (84 cases, 23.08%). The differences in unvaccinated and triple-vaccinated patients among the three groups were statistically significant (p < 0.05). The common respiratory symptoms were cough in 237 cases (65.11%) and sputum production in 199 cases (54.67%). In terms of laboratory tests, there were statistically significant differences in neutrophils, lymphocytes, red blood cells, C-reactive protein, D-dimer, aspartate aminotransferase, and creatinine among the three groups (p < 0.05). In imaging examinations, there were statistically significant differences among the three groups in terms of unilateral pulmonary inflammation, bilateral pulmonary inflammation, and bilateral pleural effusion (p < 0.05). There were statistically significant differences among the three groups in terms of antibiotic treatment, steroid treatment, oxygen therapy, nasal cannula oxygen inhalation therapy, non-invasive ventilation, and tracheal intubation ventilation (p < 0.05). Regarding clinical outcomes, there were statistically significant differences among the three groups in terms of mortality (p < 0.05). Multivariate logistic regression analysis showed that CRP (OR = 1.012, 95% CI = 1.004-1.019) and D-dimer (OR = 1.117, 95% CI = 1.021-1.224) were independent risk factors for patient mortality. The predictive value of CRP, D-dimer, and CK-MB for the risk of death was assessed. D-dimer had the highest sensitivity (95.8%) in predicting patient mortality risk, while CRP had the highest specificity (84.4%).

Conclusion

For patients with COVID-19 and concomitant cardiovascular diseases without contraindications, early administration of COVID-19 vaccines and booster shots can effectively reduce the mortality rate of severe cases. Monitoring biomarkers such as CRP, D-dimer, and CK-MB and promptly providing appropriate care can help mitigate the risk of mortality in patients.

Incidence of perioperative complications in COVID-19 survivors: Prospective observational clinical trial

BACKGROUND

As long as the COVID-19 pandemic continued, the continuation of elective surgery had been unavoidable. There is still no consensus on the timing of elective surgery in patients who have recovered from COVID-19. The primary aim of this study was to determine the effect of time after COVID-19 infection on perioperative complications.

METHODS

This prospective observational single center included adult patients who had recovered from COVID-19 and underwent surgery between February and July 2021. Data were prospectively collected from the patient and hospital database, the preoperative evaluation form and the perioperative anesthesia forms.

RESULTS

A total of 167 patients were included in our study. Preoperative COVID-19 RT-PCR test results were negative in all patients. The mean time of positive COVID-19 diagnosis was 151.0 ± 74.0 days before the day of surgery. Intraoperative general and airway complications occurred in 33 (19.8%) and 17 (10.2%) patients, respectively. Although the time from COVID-19 positivity to surgery was shorter in patients with intraoperative general and airway complications, the difference between the groups did not reach statistical significance (P = .241 and P = .133, respectively). The median time from COVID-19 positivity to surgery in patients with and without postoperative complications was 156.0 (min: 27.0-max: 305.0) and 148.5 (min: 14.0-max: 164.0) days, respectively (P = .757). In patients with and without oxygen support in the postoperative period, the median time from COVID-19 positivity to surgery was 98.0 (min: 27.0-max: 305.0) and 154.0 (min: 14.0-max: 364.0) days, respectively. In patients who received oxygen support in the postoperative period, the time from COVID-19 positivity to surgery was shorter and the difference between the groups was statistically significant (P = .014).

CONCLUSIONS

The incidence of perioperative complications decreased with increasing time after a positive SARS-CoV-2 infection, but there was no difference in perioperative complications between the groups. As the time between COVID-19 positivity and surgery increased, the need for oxygen support in the postoperative period decreased. It is not possible to share clear data on the timing of operation after SARS-CoV-2 infection.

SARS-CoV-2 clade dynamics and their associations with hospitalisations during the first two years of the COVID-19 pandemic

BACKGROUND

The COVID-19 pandemic was characterised by rapid waves of disease, carried by the emergence of new and more infectious SARS-CoV-2 virus variants. How the pandemic unfolded in various locations during its first two years has yet to be sufficiently covered. To this end, here we are looking at the circulating SARS-CoV-2 variants, their diversity, and hospitalisation rates in Estonia in the period from March 2000 to March 2022.

METHODS

We sequenced a total of 27,550 SARS-CoV-2 samples in Estonia between March 2020 and March 2022. High-quality sequences were genotyped and assigned to Nextstrain clades and Pango lineages. We used regression analysis to determine the dynamics of lineage diversity and the probability of clade-specific hospitalisation stratified by age and sex.

RESULTS

We successfully sequenced a total of 25,375 SARS-CoV-2 genomes (or 92%), identifying 19 Nextstrain clades and 199 Pango lineages. In 2020 the most prevalent clades were 20B and 20A. The various subsequent waves of infection were driven by 20I (Alpha), 21J (Delta) and Omicron clades 21K and 21L. Lineage diversity via the Shannon index was at its highest during the Delta wave. About 3% of sequenced SARS-CoV-2 samples came from hospitalised individuals. Hospitalisation increased markedly with age in the over-forties, and was negligible in the under-forties. Vaccination decreased the odds of hospitalisation in over-forties. The effect of vaccination on hospitalisation rates was strongly dependent upon age but was clade-independent. People who were infected with Omicron clades had a lower hospitalisation likelihood in age groups of forty and over than was the case with pre-Omicron clades regardless of vaccination status.

CONCLUSIONS

COVID-19 disease waves in Estonia were driven by the Alpha, Delta, and Omicron clades. Omicron clades were associated with a substantially lower hospitalisation probability than pre-Omicron clades. The protective effect of vaccination in reducing hospitalisation likelihood was independent of the involved clade.

California's COVID-19 Vaccine Equity Policy: Cases, Hospitalizations, And Deaths Averted In Affected Communities

In March 2021, California implemented a vaccine equity policy that prioritized COVID-19 vaccine allocation to communities identified as least advantaged by an area-based socioeconomic measure, the Healthy Places Index. We conducted quasi-experimental and counterfactual analyses to estimate the effect of this policy on COVID-19 vaccination, case, hospitalization, and death rates. Among prioritized communities, vaccination rates increased 28.4 percent after policy implementation. Furthermore, an estimated 160,892 COVID-19 cases, 10,248 hospitalizations, and 679 deaths in the least-advantaged communities were averted by the policy. Despite these improvements, the share of COVID-19 cases, hospitalizations, and deaths in prioritized communities remained elevated. These estimates were robust in sensitivity analyses that tested exchangeability between prioritized communities and those not prioritized by the policy; model specifications; and potential temporal confounders, including prior infections. Correcting for disparities by strategically allocating limited resources to the least-advantaged or most-affected communities can reduce the impacts of COVID-19 and other diseases but might not eliminate health disparities.

Diagnostics for Public Health - Infectious Disease Surveillance and Control

AbstractAccurate diagnostics are critical in public health to ensure successful disease tracking, prevention, and control. Many of the same characteristics are desirable for diagnostic procedures in both medicine and public health: for example, low cost, high speed, low invasiveness, ease of use and interpretation, day-to-day consistency, and high accuracy. This review lays out five principles that are salient when the goal of diagnosis is to improve the overall health of a population rather than that of a particular patient, and it applies them in two important use cases: pandemic infectious disease and antimicrobial resistance.

Characteristics and outcomes of COVID-19 patients presumed to be treated with sotrovimab in NHS hospitals in England

BACKGROUND

The impact of the constantly evolving severe acute respiratory syndrome coronavirus 2 on the effectiveness of early coronavirus disease 2019 (COVID-19) treatments is unclear. Here, we report characteristics and acute clinical outcomes of patients with COVID-19 treated with a monoclonal antibody (mAb; presumed to be sotrovimab) across six distinct periods covering the emergence and predominance of Omicron subvariants (BA.1, BA.2, and BA.5) in England.

METHODS

Retrospective cohort study using data from the Hospital Episode Statistics database from January 1-July 31, 2022. Included patients received a mAb delivered by a National Health Service (NHS) hospital as a day-case, for which the primary diagnosis was COVID-19. Patients were presumed to have received sotrovimab based on NHS data showing that 99.98% of COVID-19-mAb-treated individuals received sotrovimab during the study period. COVID-19-attributable hospitalizations were reported overall and across six distinct periods of Omicron subvariant prevalence. Subgroup analyses were conducted in patients with severe renal disease and active cancer.

RESULTS

Among a total of 10,096 patients, 1.0% (n = 96) had a COVID-19-attributable hospitalization, 4.6% (n = 465) had a hospital visit due to any cause, and 0.3% (n = 27) died due to any cause during the acute period. COVID-19-attributable hospitalization rates were consistent among subgroups, and no significant differences were observed across periods of Omicron subvariant predominance.

CONCLUSIONS

Levels of COVID-19-attributable hospitalizations and deaths were low in mAb-treated patients and among subgroups. Similar hospitalization rates were observed whilst Omicron BA.1, BA.2, and BA.5 were predominant, despite reported reductions in in vitro neutralization activity of sotrovimab against BA.2 and BA.5.

Immune escape and attenuated severity associated with the SARS-CoV-2 BA.2.86/JN.1 lineage

The SARS-CoV-2 BA.2.86 lineage, and its sublineage JN.1 in particular, achieved widespread transmission in the US during winter 2023-24. However, the increase in infections was not accompanied by increases in COVID-19 hospitalizations and mortality commensurate with prior waves. To understand shifts in COVID-19 epidemiology associated with JN.1 emergence, we compared characteristics and clinical outcomes of time-matched cases infected with BA.2.86- derived lineages (predominantly representing JN.1) versus co-circulating XBB-derived lineages in December, 2023 and January, 2024. Cases infected with BA.2.86-derived lineages received greater numbers of COVID-19 vaccine doses, including XBB.1.5-targeted and BA.4/BA.5-targeted boosters, in comparison to cases infected with XBB-derived lineages. Additionally, cases infected with BA.2.86-derived lineages experienced greater numbers of documented prior SARS-CoV-2 infections. These associations of BA.2.86-derived lineages with immune escape were confirmed when comparing cases diagnosed during periods when JN.1 was the predominant circulating lineage to cases diagnosed during November, 2023. Cases infected with BA.2.86-derived lineages, or during periods when JN.1 was the predominant circulating lineage, also experienced lower risk of progression to severe clinical outcomes requiring emergency department consultations or hospital admission. Sensitivity analyses suggested under-ascertainment of prior infections, even if differential between cases infected with BA.2.86-derived lineages and non-BA.2.86 lineages, could not explain this apparent attenuation of severity. Our findings implicate escape from immunity acquired from prior vaccination or infection in the emergence of the JN.1 lineage and suggest infections with this lineage are less likely to experience clinically-severe disease. Monitoring of immune escape and clinical severity in emerging SARS-CoV-2 variants remains a priority to inform responses.

Factors Associated with Mortality Among Severe Omicron Patients for COVID-19

Purpose

The purpose of the study was to explore the potential risk factors of mortality in patients with severe pneumonia during the omicron pandemic in South China in 2022.

Methods

Clinical data was collected from patients hospitalized with omicron COVID-19. Then, patients were categorized into the non-survival and survival groups. A comprehensive analysis was conducted to analyze the factors associated with negative outcome in individuals suffering from severe omicron COVID-19.

Results

In this study, 155 severe COVID-19 patients were included, comprising 55 non-survivors and 100 survivors. Non-survivors, in comparison to survivors, exhibited elevated levels of various biomarkers including neutrophil count, hypersensitive troponin T, urea, creatinine, C-reactive protein, procalcitonin, interleukin-6, plasma D-dimer, and derived neutrophil-to-lymphocyte ratio (dNLR) (P < 0.05). They also displayed reduced lymphocyte count, platelet count, and albumin levels (P < 0.05) and were more prone to developing comorbidities, including shock, acute cardiac and renal injury, acute respiratory distress syndrome, coagulation disorders, and secondary infections. Platelet count (PLT) <100 × 10^/L, interleukin-6 (IL-6) >100 pg/mL, and dNLR >5.0 independently contributed to the risk of death in patients suffering from severe COVID-19.

Conclusion

PLT, IL-6, and dNRL independently contributed to the risk of mortality in patients with severe pneumonia during the 2022 omicron pandemic in South China.

Effectiveness of remdesivir-based therapy for moderate COVID-19: comparison of Omicron and other variant phases

Remdesivir is an antiviral drug for the treatment of coronavirus disease 2019 (COVID-19), and the sustained antiviral activity against Omicron variants of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been reported. In this single-center retrospective study, we first compared the clinical effectiveness of remdesivir-based therapy between Omicron and other variant phases of moderate COVID-19 in a real-world setting. Between Dec 2020 and July 2022, a total of 406 patients with COVID-19 pneumonia were treated with remdesivir-based therapy on admission. The oxygen deterioration rate after initiation of treatment significantly decreased in the Omicron variant phase compared to the alpha and delta variant phases. In an adjusted multivariate Cox proportional hazards model, Omicron variant phase was significantly associated with delayed oxygen deterioration and early recovery from hypoxia. These favorable outcomes during the Omicron variant phase, compared to previous variant phases, might be due to the attenuation and the popularization of vaccination.

Risk of subsequent SARS-CoV-2 infection among vaccinated employees with or without hybrid immunity acquired early in the Omicron-predominant era of the COVID-19 pandemic

BACKGROUND

Hybrid immunity, from COVID-19 vaccination followed by SARS-CoV-2 infection acquired after its Omicron variant began predominating, has provided greater protection than vaccination alone against subsequent infection over 1-3 months of observation. Its longer-term protection is unknown.

METHODS

We conducted a retrospective cohort study of COVID-19 case incidence among healthcare personnel (HCP) mandated to be vaccinated and report on COVID-19-associated symptoms, high-risk exposures, or known-positive test results to an employee health hotline. We compared cases with hybrid immunity, defined as incident COVID-19 during the first 6 weeks of Omicron-variant predominance (run-in period), to those with immunity from vaccination alone during the run-in period. Time until COVID-19 infection over 13 subsequent months (observation period) was analyzed by standard survival analysis.

RESULTS

Of 5867 employees, 641 (10.9%, 95% confidence interval [CI]: 10.1%-11.8%) acquired hybrid immunity during the run-in period. Of these, 104 (16.2%, 95% CI: 13.5%-19.3%) experienced new SARS-CoV-2 infection during the 13-month observation period, compared to 2177 (41.7%, 95% CI: 40.3%-43.0%) of the 5226 HCP without hybrid immunity. Time until incident infection was shorter among the latter (hazard ratio: 3.09, 95% CI: 2.54-3.78).

CONCLUSIONS

In a cohort of vaccinated employees, Omicron-era acquired SARS-CoV-2 hybrid immunity was associated with significantly lower risk of subsequent infection over more than a year of observation-a time period far longer than previously reported and during which three, progressively more resistant, Omicron subvariants became predominant. These findings can inform institutional policy and planning for future COVID-19 additional vaccine dosing requirements for employees, for surveillance programs, and for risk modification efforts.

COVID-19 Vaccination and Incidence of Pediatric SARS-CoV-2 Infection and Hospitalization

Importance

A SARS-CoV-2 vaccine was approved for adolescents aged 12 to 15 years on May 10, 2021, with approval for younger age groups following thereafter. The population level impact of the pediatric COVID-19 vaccination program has not yet been established.

Objective

To identify whether California's pediatric COVID-19 immunization program was associated with changes in pediatric COVID-19 incidence and hospitalizations.

Design, Setting, and Participants

A case series on COVID-19 vaccination including children aged 6 months to 15 years was conducted in California. Data were obtained on COVID-19 cases in California between April 1, 2020, and February 27, 2023.

Exposure

Postvaccination evaluation periods spanned 141 days (June 10 to October 29, 2021) for adolescents aged 12 to 15 years, 199 days (November 29, 2021, to June 17, 2022) for children aged 5 to 11 years, and 225 days (July 17, 2022, to February 27, 2023) for those aged 6 to 59 months. During these periods, statewide vaccine coverage reached 53.5% among adolescents aged 12 to 15 years, 34.8% among children aged 5 to 11 years, and 7.9% among those aged 6 to 59 months.

Main Outcomes and Measures

Age-stepped implementation of COVID-19 vaccination was used to compare observed county-level incidence and hospitalization rates during periods when each age group became vaccine eligible to counterfactual rates predicted from observations among other age groups. COVID-19 case and hospitalization data were obtained from the California reportable disease surveillance system.

Results

Between April 1, 2020, and February 27, 2023, a total of 3 913 063 pediatric COVID-19 cases and 12 740 hospitalizations were reported in California. Reductions of 146 210 cases (95% prediction interval [PI], 136 056-158 948) were estimated among adolescents aged 12 to 15 years, corresponding to a 37.1% (35.5%-39.1%) reduction from counterfactual predictions. Reductions of 230 134 (200 170-265 149) cases were estimated among children aged 5 to 11 years, corresponding to a 23.7% (20.6%-27.3%) reduction from counterfactual predictions. No evidence of reductions in COVID-19 cases statewide were found among children aged 6 to 59 months (estimated averted cases, -259; 95% PI, -1938 to 1019), although low transmission during the evaluation period may have limited the ability to do so. An estimated 168 hospitalizations (95% PI, 42-324) were averted among children aged 6 to 59 months, corresponding to a 24.4% (95% PI, 6.1%-47.1%) reduction. In meta-analyses, county-level vaccination coverage was associated with averted cases for all age groups. Despite low vaccination coverage, pediatric COVID-19 immunization in California averted 376 085 (95% PI, 348 355-417 328) reported cases and 273 (95% PI, 77-605) hospitalizations among children aged 6 months to 15 years over approximately 4 to 7 months following vaccination availability.

Conclusions and Relevance

The findings of this case series analysis of 3 913 063 cases suggest reduced pediatric SARS-CoV-2 transmission following immunization. These results support the use of COVID-19 vaccines to reduce COVID-19 incidence and hospitalization in pediatric populations.

Clinical features of patients with rheumatic and musculoskeletal diseases during the coronavirus disease 2019 pandemic and the association of its relapse with infection: Across-sectional study

AIM

The aim of this study was to investigate the clinical features of patients with rheumatic and musculoskeletal diseases (RMDs) infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the relationship between RMDs relapse and SARS-CoV-2 infection.

METHODS

We carried out a cross-sectional observational study among 585 patients with RMDs and 619 individuals without RMDs. Data on demographics, the clinical features of coronavirus disease 2019 (COVID-19), antirheumatic therapy, and RMD relapse were collected. Differences between RMDs and control groups, infected and uninfected groups, relapse and non-relapse RMDs groups were examined. The influence of COVID-19 infection on medications and relapse of RMDs was also assessed.

RESULTS

Among 1204 participants finally recruited for analysis, 1030 (85.5%) were infected with COVID-19. Seven hundred and ninety-five (77.2%) of infected individuals were female, and the median age was 40 years (IQR 33, 50). Patients in the RMD group had a relatively lower risk of COVID-19 symptoms whereas were significantly more likely to require hospitalization (6.7% vs. 2.2%). In the RMDs group, younger patients who were under the age of 65 were more likely to report more symptoms. More patients with RMD relapse (27, 34.6%) adjusted their medications during the period of COVID-19 infection than those without relapse (59, 13.2%).

CONCLUSION

Patients with RMDs were at lower risk of symptoms of COVID-19. Rheumatic and musculoskeletal disease patients experience a higher risk of relapse especially when they adjust medications during COVID-19 infection. The long-term prognosis of infected RMDs patients need further investigation.

Artificial Neural Network Prediction of COVID-19 Daily Infection Count

This study addresses COVID-19 testing as a nonlinear sampling problem, aiming to uncover the dependence of the true infection count in the population on COVID-19 testing metrics such as testing volume and positivity rates. Employing an artificial neural network, we explore the relationship among daily confirmed case counts, testing data, population statistics, and the actual daily case count. The trained artificial neural network undergoes testing in in-sample, out-of-sample, and several hypothetical scenarios. A substantial focus of this paper lies in the estimation of the daily true case count, which serves as the output set of our training process. To achieve this, we implement a regularized backcasting technique that utilize death counts and the infection fatality ratio (IFR), as the death statistics and serological surveys (providing the IFR) as more reliable COVID-19 data sources. Addressing the impact of factors such as age distribution, vaccination, and emerging variants on the IFR time series is a pivotal aspect of our analysis. We expect our study to enhance our understanding of the genuine implications of the COVID-19 pandemic, subsequently benefiting mitigation strategies.

Clinical characteristics and outcomes of liver transplant recipients infected by Omicron during the opening up of the dynamic zero-coronavirus disease policy in China: A prospective, observational study

We analyzed the characteristics, risk factors, outcomes, and post-coronavirus disease 2019 (COVID-19) symptoms in liver transplant recipients in China's late 2022 COVID-19 wave. Recipients with COVID-19 were enrolled from December 1, 2022, to January 31, 2023, and followed up until May 31, 2023. Baseline and characteristic data were collected. A total of 930 recipients were included, with a vaccination rate (non-mRNA) of 40.0%. Among 726 (78.1%) recipients with COVID-19, 641 (88.3%) patients were treated at home, 81 (11.2%) patients required hospitalization in general wards, 4 (0.6%) patients required intensive care, and 1 (0.1%) patient died because of COVID-19. Severe acute respiratory syndrome coronavirus 2 infection was related to close contact with confirmed cases (P < .001) and the condition of end-stage kidney disease (P < .046). Older age, male sex, less vaccination, and hypertension were independent risk factors for hospitalization. Fatigue (36.9%) was the most common symptom post-COVID-19, followed by memory loss (35.7%) and sleep disturbance (23.9%). Two doses of vaccines had a protective effect against these post-COVID-19 symptoms (P < .05). During this Omicron outbreak, liver transplant recipients were susceptible to COVID-19, with frequent hospitalization but low mortality. Two doses of non-mRNA COVID-19 vaccines could protect against liver transplant recipient hospitalization and post-COVID-19 symptoms.

Pneumonia Caused by Chlamydia psittaci and SARS-CoV-2 Coinfection Diagnosed Using Metagenomic Next-Generation Sequencing: A Case Report

We report a case of pneumonia caused by coinfection with Chlamydia psittaci and the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron XBB.1 variant, confirmed using metagenomic next-generation sequencing (mNGS) and quantitative polymerase chain reaction (qPCR). C. psittaci and SARS-CoV-2 were detected in bronchoalveolar lavage fluid using mNGS. Additionally, mNGS detected C. psittaci in blood and nasopharyngeal specimens and was more sensitive than qPCR. The patient recovered after treatment with moxifloxacin. This report highlights the use of coinfections of C. psittaci and SARS-CoV-2, as mNGS has already been recognized to be a diagnostic tool for identifying coinfections.

SARS-CoV-2 Omicron Infections among Vaccinated Maintenance Hemodialysis Patients: Outcomes and Comparison to Delta Variant

BACKGROUND

Infections with B.1.1.529 (Omicron) variants of SARS-CoV-2 became predominant worldwide since late 2021, replacing the previously dominant B.1.617.2 variant (Delta). While those variants are highly transmissible and can evade vaccine protection, population studies suggested that outcomes from infection with Omicron variants are better compared with Delta. Data regarding prognosis of maintenance hemodialysis (MHD) patients infected with Omicron versus Delta variants, however, are scarce.

METHODS

This retrospective cohort study includes all patients with end-stage kidney disease treated with MHD in Meir Medical Center, Kfar-Saba, Israel, that were diagnosed with SARS-CoV-2 infection between June 2021 and May 2022.

RESULTS

Twenty-six subjects were diagnosed with the Delta variant and 71 with Omicron. Despite comparable age between groups and higher mean vaccine doses prior to the infection among the Omicron group (p < 0.001), SARS-CoV-2 infection severity was significantly worse among MHD infected with the Delta variant: 50% developed severe or critical COVID-19 versus 5% in the Omicron group (p < 0.001). Over half of MHD infected with Omicron (57%) were asymptomatic during their illness. The 30-day mortality rate for the whole cohort was 5.2%. It was significantly higher among MHD in the Delta group than in the Omicron group (5/26, 19.2% vs. 0/71, p < 0.001), as was the 90-day mortality rate (5/26, 19.2% vs. 3/71, 4.2%, p = 0.02).

CONCLUSIONS

Infection with the SARS-CoV-2 Delta variant was associated with worse outcomes compared with Omicron, among subjects on MHD. However, despite mild disease among vaccinated MHD patients, infection with Omicron variant was still associated with the significant 90-day mortality rate.

Acute ischemic stroke outcomes in patients with COVID-19: a systematic review and meta-analysis

BACKGROUND

Although patients with COVID-19 have a higher risk of acute ischemic stroke (AIS), the impact on stroke outcomes remains uncertain.

AIMS

To determine the clinical outcomes of patients with AIS and COVID-19 (AIS-COVID+).

METHODS

We performed a systematic review and meta-analysis following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. Our protocol was registered with the International Prospective Register of Systematic Reviews (CRD42020211977). Systematic searches were last performed on June 3, 2021 in EMBASE, PubMed, Web-of-Science, Scopus, and CINAHL Databases.

INCLUSION CRITERIA

(1) studies reporting outcomes on AIS-COVID+; (2) original articles published in 2020 or later; (3) study participants aged ≥18 years.

EXCLUSION CRITERIA

(1) case reports with <5 patients, abstracts, review articles; (2) studies analyzing novel interventions. Risk of bias was assessed using the Mixed Methods Appraisal Tool. Random-effects models estimated the pooled OR and 95% confidence intervals (95% CI) for mortality, modified Rankin Scale (mRS) score, length of stay (LOS), and discharge disposition.

RESULTS

Of the 43 selected studies, 46.5% (20/43) reported patients with AIS without COVID-19 (AIS-COVID-) for comparison. Random-effects model included 7294 AIS-COVID+ and 158 401 AIS-COVID-. Compared with AIS-COVID-, AIS-COVID+ patients had higher in-hospital mortality (OR=3.87 (95% CI 2.75 to 5.45), P<0.001), less mRS scores 0-2 (OR=0.53 (95% CI 0.46 to 0.62), P<0.001), longer LOS (mean difference=4.21 days (95% CI 1.96 to 6.47), P<0.001), and less home discharge (OR=0.31 (95% CI 0.21 to 0.47), P<0.001).

CONCLUSIONS

Patients with AIS-COVID had worse outcomes, with almost fourfold increased mortality, half the odds of mRS scores 0-2, and one-third the odds of home discharge. These findings confirm the significant impact of COVID-19 on early stroke outcomes.

Molecular insights into the adaptive evolution of SARS-CoV-2 spike protein

The COVID-19 pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has substantially damaged the global economy and human health. The spike (S) protein of coronaviruses plays a pivotal role in viral entry by binding to host cell receptors. Additionally, it acts as the primary target for neutralizing antibodies in those infected and is the central focus for currently utilized or researched vaccines. During the virus's adaptation to the human host, the S protein of SARS-CoV-2 has undergone significant evolution. As the COVID-19 pandemic has unfolded, new mutations have arisen and vanished, giving rise to distinctive amino acid profiles within variant of concern strains of SARS-CoV-2. Notably, many of these changes in the S protein have been positively selected, leading to substantial alterations in viral characteristics, such as heightened transmissibility and immune evasion capabilities. This review aims to provide an overview of our current understanding of the structural implications associated with key amino acid changes in the S protein of SARS-CoV-2. These research findings shed light on the intricate and dynamic nature of viral evolution, underscoring the importance of continuous monitoring and analysis of viral genomes. Through these molecular-level investigations, we can attain deeper insights into the virus's adaptive evolution, offering valuable guidance for designing vaccines and developing antiviral drugs to combat the ever-evolving viral threats.

Comparing COVID-19 severity in patients hospitalized for community-associated Delta, BA.1 and BA.4/5 variant infection

Background

Despite decreasing COVID-19 disease severity during the Omicron waves, a proportion of patients still require hospitalization and intensive care.

Objective

To compare demographic characteristics, comorbidities, vaccination status, and previous infections in patients hospitalized for community-associated COVID-19 (CAC) in predominantly Delta, Omicron BA.1 and BA.4/5 SARS-CoV-2 waves.

Methods

Data were extracted from three national databases-the National COVID-19 Database, National Vaccination Registry and National Registry of Hospitalizations.

Results

Among the hospitalized CAC patients analyzed in this study, 5,512 were infected with Delta, 1,120 with Omicron BA.1, and 1,143 with the Omicron BA.4/5 variant. The age and sex structure changed from Delta to BA.4/5, with the proportion of women (9.5% increase), children and adolescents (10.4% increase), and octa- and nonagenarians increasing significantly (24.5% increase). Significantly more patients had comorbidities (measured by the Charlson Comorbidity Index), 30.3% in Delta and 43% in BA.4/5 period. The need for non-invasive ventilatory support (NiVS), ICU admission, mechanical ventilation (MV), and in-hospital mortality (IHM) decreased from Delta to Omicron BA.4/5 period for 12.6, 13.5, 11.5, and 6.3%, respectively. Multivariate analysis revealed significantly lower odds for ICU admission (OR 0.68, CI 0.54-0.84, p < 0.001) and IHM (OR 0.74, CI 0.58-0.93, p = 0.011) during the Delta period in patients who had been fully vaccinated or boosted with a COVID-19 vaccine within the previous 6 months. In the BA.1 variant period, patients who had less than 6 months elapsed between the last vaccine dose and SARS-CoV-2 positivity had lower odds for MV (OR 0.38, CI 0.18-0.72, p = 0.005) and IHM (OR 0.56, CI 0.37- 0.83, p = 0.005), but not for NIVS or ICU admission.

Conclusion

The likelihood of developing severe CAC in hospitalized patients was higher in those with the Delta and Omicron BA.1 variant compared to BA.4/5.

Quantifying how much host, pathogen, and other factors affect human protective adaptive immune responses

Recognizing the "essential" factors that contribute to a clinical outcome is critical for designing appropriate therapies and prioritizing limited medical resources. Demonstrating a high correlation between a factor and an outcome does not necessarily imply an essential role of the factor to the outcome. Human protective adaptive immune responses to pathogens vary among (and perhaps within) pathogenic strains, human individual hosts, and in response to other factors. Which of these has an "essential" role? We offer three statistical approaches that predict the presence of newly contributing factor(s) and then quantify the influence of host, pathogen, and the new factors on immune responses. We illustrate these approaches using previous data from the protective adaptive immune response (cellular and humoral) by human hosts to various strains of the same pathogenic bacterial species. Taylor's law predicts the existence of other factors potentially contributing to the human protective adaptive immune response in addition to inter-individual host and intra-bacterial species inter-strain variability. A mixed linear model measures the relative contribution of the known variables, individual human hosts and bacterial strains, and estimates the summed contributions of the newly predicted but unknown factors to the combined adaptive immune response. A principal component analysis predicts the presence of sub-variables (currently not defined) within bacterial strains and individuals that may contribute to the combined immune response. These observations have statistical, biological, clinical, and therapeutic implications.

COVID-19 passenger screening to reduce travel risk and translocation of disease

Aviation passenger screening has been used worldwide to mitigate the translocation risk of SARS-CoV-2. We present a model that evaluates factors in screening strategies used in air travel and assess their relative sensitivity and importance in identifying infectious passengers. We use adapted Monte Carlo simulations to produce hypothetical disease timelines for the Omicron variant of SARS-CoV-2 for travelling passengers. Screening strategy factors assessed include having one or two RT-PCR and/or antigen tests prior to departure and/or post-arrival, and quarantine length and compliance upon arrival. One or more post-arrival tests and high quarantine compliance were the most important factors in reducing pathogen translocation. Screening that combines quarantine and post-arrival testing can shorten the length of quarantine for travelers, and variability and mean testing sensitivity in post-arrival RT-PCR and antigen tests decrease and increase with the greater time between the first and second post-arrival test, respectively. This study provides insight into the role various screening strategy factors have in preventing the translocation of infectious diseases and a flexible framework adaptable to other existing or emerging diseases. Such findings may help in public health policy and decision-making in present and future evidence-based practices for passenger screening and pandemic preparedness.

Clinical course and management of COVID-19 in the era of widespread population immunity

The clinical implications of COVID-19 have changed since SARS-CoV-2 first emerged in humans. The current high levels of population immunity, due to prior infection and/or vaccination, have been associated with a vastly decreased overall risk of severe disease. Some people, particularly those with immunocompromising conditions, remain at risk for severe outcomes. Through the course of the pandemic, variants with somewhat different symptom profiles from the original SARS-CoV-2 virus have emerged. The management of COVID-19 has also changed since 2020, with the increasing availability of evidence-based treatments in two main classes: antivirals and immunomodulators. Selecting the appropriate treatment(s) for patients with COVID-19 requires a deep understanding of the evidence and an awareness of the limitations of applying data that have been largely based on immune-naive populations to patients today who most likely have vaccine-derived and/or infection-derived immunity. In this Review, we provide a summary of the clinical manifestations and approaches to caring for adult patients with COVID-19 in the era of vaccine availability and the dominance of the Omicron subvariants, with a focus on the management of COVID-19 in different patient groups, including immunocompromised, pregnant, vaccinated and unvaccinated patients.

SARS-CoV-2 Omicron (BA.4, BA.5) variant: Lessons learned from a new variant during the COVID-19 pandemic

Background and Aim

In late 2021, the world faced the rapid spread of the SARS-CoV-2 Omicron variant, which quickly became the variant of concern. In April 2022, two new lineages of Omicron (BA.4/BA.5) emerged from Africa, where they caused the fifth wave of infection.

Method

We searched PubMed, Google Scholar, and Scopus online databases up to December 2023 for founding relevant studies.

Results

BA.4 and BA.5 subgroups, with changes in the spike protein, have a greater ability to escape from the immune system, which was possible with the help of L452R and F486V mutations. Epidemiologically, these evolving subtypes show similarities to seasonal influenza but with higher mortality rates. The symptoms of these subgroups are different from the previous types in the form of upper respiratory symptoms. Antiviral treatments, the use of antibodies such as bebtelovimab, and the development of vaccines are promising.

Conclusion

Consequently, we must continue to be vigilant in our joint surveillance efforts against COVID-19 in diagnosis and treatment.

Effectiveness of nirmatrelvir-ritonavir on severe outcomes of COVID-19 in the era of vaccination and Omicron: An updated meta-analysis

Nirmatrelvir-ritonavir (NR) was approved to treat SARS-CoV-2 positive outpatients at high risk of progression to severe disease, based on a randomized trial in unvaccinated patients. Effectiveness in vaccinated patients and against Omicron has not yet been confirmed by clinical trial data, but a recent meta-analysis suggested good real-world effectiveness based on 12 studies. We updated this meta-analysis by searching Medline and Embase databases for studies assessing effectiveness of NR on mortality, hospitalization, composite outcome of hospitalization and/or death, and progression to severe disease, published between October 1, 2022 and May 22, 2023. Random effects meta-analysis and subgroup analysis for vaccinated patients was performed. A total of 32 studies were included in the meta-analysis. Pooled RR for the effect of NR on mortality, hospitalization, hospitalization and/or mortality, and progression to severe disease were 0.36 (95% confidence interval [CI]: 0.25-0.52), 0.43 (CI: 0.37-0.51), 0.52 (CI: 0.45-0.61) and 0.54 (CI: 0.41-0.73), respectively. A subgroup analysis on vaccinated patients indicated lower effectiveness of NR on mortality (RR: 0.55, CI: 0.45-0.68), but similar effectiveness for hospitalization, hospitalization and/or mortality, or progression to severe disease (RR: 0.52, 0.58, and 0.66, respectively). This updated meta-analysis robustly confirms the protective effects of NR on severe COVID-19 outcomes.

Clinical factors associated with viral shedding time of SARS-CoV-2 Omicron variant in Japan

The Omicron variant of severe acute respiratory syndrome coronavirus 2 exhibits increased infectivity compared with all prior variants, and the timing of quarantine release should be carefully considered. However, to date, only two Chinese studies have analyzed the association between the viral shedding time (VST) and risk factors among patients infected with the Omicron variant. These studies included only limited numbers of severe cases and no analysis of underlying diseases and immunosuppressive drug use. Therefore, the current study aimed to analyze them in Japan. This retrospective observational study was conducted at the University of Occupational and Environmental Health, Japan, from January 2022 to October 2022 and included 87 hospitalized patients and 305 healthcare workers (HCWs) with coronavirus 2019 (COVID-19). In comparison with HCWs, hospitalized patients were significantly older and had a higher proportion of severe COVID-19 cases and significantly longer VST. A simple regression analysis showed that severe, current, or ex-smoking status, cardiovascular diseases, chronic kidney disease, and use of corticosteroids for underlying diseases were significantly correlated with a longer VST. Moreover, multiple linear regression analysis revealed that cardiovascular diseases, chronic kidney disease, and corticosteroid use were significantly associated with a longer VST. Therefore, COVID-19 patients with these underlying diseases may require a longer isolation period and the timing of quarantine release should be carefully considered.

COVID-19 waves in an urban setting 2020-2022: an electronic medical record analysis

Background

Global and national surveillance efforts have tracked COVID-19 incidence and clinical outcomes, but few studies have compared comorbid conditions and clinical outcomes across each wave of the pandemic. We analyzed data from the COVID-19 registry of a large urban healthcare system to determine the associations between presenting comorbidities and clinical outcomes during the pandemic.

Methods

We analyzed registry data for all inpatients and outpatients with COVID-19 from March 2020 through September 2022 (N = 44,499). Clinical outcomes were death, hospitalization, and intensive care unit (ICU) admission. Demographic and clinical outcomes data were analyzed overall and for each wave. Unadjusted and multivariable logistic regressions were performed to explore the associations between age, sex, race, ethnicity, comorbidities, and mortality.

Results

Waves 2 and 3 (Alpha and Delta variants) were associated with greater hospitalizations, ICU admissions, and mortality than other variants. Chronic pulmonary disease was the most common comorbid condition across all age groups and waves. Mortality rates were higher in older patients but decreased across all age groups in later waves. In every wave, mortality was associated with renal disease, congestive heart failure, cerebrovascular disease, diabetes, and chronic pulmonary disease. Multivariable analysis found that liver disease and renal disease were significantly associated with mortality, hospitalization, and ICU admission, and diabetes was significantly associated with hospitalization and ICU admission.

Conclusion

The COVID-19 registry is a valuable resource to identify risk factors for clinical outcomes. Our findings may inform risk stratification and care planning for patients with COVID-19 based on age and comorbid conditions.

Vitamin D Supplementation and Prior Oral Poliovirus Vaccination Decrease Odds of COVID-19 Outcomes among Adults Recently Inoculated with Inactivated Poliovirus Vaccine

BACKGROUND

Structural and functional commonalities between poliovirus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) suggest that poliovirus inoculation may induce antibodies that mitigate the coronavirus disease (COVID-19). No known studies have evaluated COVID-19 risk factors in adults recently vaccinated against poliovirus.

STUDY OBJECTIVE

Among adults with no history of COVID-19 infection or vaccination, who recently received an inactivated poliovirus vaccine (IPV), we sought to determine which biological factors and social determinants of health (SDOH) may be associated with (1) testing positive for SARS-CoV-2, (2) experiencing COVID-19 symptoms, and (3) a longer duration of COVID-19 symptoms.

METHODS

The influence of biological factors and SDOH on SARS-CoV-2 infection and COVID-19 symptoms were evaluated among 282 adults recently inoculated with IPV. Participant-reported surveys were analyzed over 12 months post-enrollment. Bivariate and multivariate linear and logistic regression models identified associations between variables and COVID-19 outcomes.

RESULTS

Adjusting for COVID-19 vaccinations, variants, and other SDOH, secondary analyses revealed that underlying conditions, employment, vitamin D, education, and the oral poliovirus vaccination (OPV) were associated with COVID-19 outcomes. The odds of testing positive for SARS-CoV-2 and experiencing symptoms were significantly reduced among participants who took vitamin D (OR 0.12 and OR 0.09, respectively). Unemployed or part-time working participants were 72% less likely to test positive compared with full-time workers. No prior dose of OPV was one of the strongest predictors of SARS-CoV-2 infection (OR 4.36) and COVID-19 symptoms (OR 6.95).

CONCLUSIONS

Findings suggest that prophylactic measures and mucosal immunity may mitigate the risk and severity of COVID-19 outcomes. Larger-scale studies may inform future policies.

Evolution of illness severity in hospital admissions due to COVID-19, Québec, Canada, January to April 2022

Background

The coronavirus disease 2019 (COVID-19) severity is influenced by multiple factors, such as age, underlying medical conditions, individual immunity, infecting variant, and clinical practice. The highly transmissible Omicron variants resulted in decreased COVID-19 screening capacity, which limited disease severity surveillance.

Objective

To report on the temporal evolution of disease severity among patients admitted to Québec hospitals due to COVID-19 between January 2, 2022, and April 23, 2022, which corresponded to the peak period of hospitalizations due to Omicron.

Methods

Retrospective population-based cohort study of all hospital admissions due to COVID-19 in Québec, between January 2, 2022, and April 23, 2022. Study period was divided into four-week periods, corresponding roughly to January, February, March and April. Regression using Cox and Poisson generalized estimating equations (GEEs) was used to quantify temporal variations in length of stay and risk of complications (intensive care admission or in-hospital death) through time, using the Omicron peak (January 2022) as reference. Measures were adjusted for age, sex, vaccination status, presence of chronic diseases, and clustering by hospital.

Results

During the study period, 9,178 of all 18,272 (50.2%) patients hospitalized with a COVID-19 diagnosis were admitted due to COVID-19. Of these, 1,026 (11.2%) were admitted to intensive care and 1,523 (16.6%) died. Compared to January, the risk of intensive care admission was 25% and 31% lower in March and April respectively, while in-hospital fatality continuously decreased by 45% lower in April. The average length of stay was temporarily lower in March (9%).

Conclusion

Severity of admissions due to COVID-19 decreased in the first months of 2022, when predominant circulating variants were considered to be of similar severity. Monitoring hospital admissions due to COVID-19 can contribute to disease severity surveillance.

Divergent trajectory of replication and intrinsic pathogenicity of SARS-CoV-2 Omicron post-BA.2/5 subvariants in the upper and lower respiratory tract

BACKGROUND

Earlier Omicron subvariants including BA.1, BA.2, and BA.5 emerged in waves, with a subvariant replacing the previous one every few months. More recently, the post-BA.2/5 subvariants have acquired convergent substitutions in spike that facilitated their escape from humoral immunity and gained ACE2 binding capacity. However, the intrinsic pathogenicity and replication fitness of the evaluated post-BA.2/5 subvariants are not fully understood.

METHODS

We systemically investigated the replication fitness and intrinsic pathogenicity of representative post-BA.2/5 subvariants (BL.1, BQ.1, BQ.1.1, XBB.1, CH.1.1, and XBB.1.5) in weanling (3-4 weeks), adult (8-10 weeks), and aged (10-12 months) mice. In addition, to better model Omicron replication in the human nasal epithelium, we further investigated the replication capacity of the post-BA.2/5 subvariants in human primary nasal epithelial cells.

FINDINGS

We found that the evaluated post-BA.2/5 subvariants are consistently attenuated in mouse lungs but not in nasal turbinates when compared with their ancestral subvariants BA.2/5. Further investigations in primary human nasal epithelial cells revealed a gained replication fitness of XBB.1 and XBB.1.5 when compared to BA.2 and BA.5.2.

INTERPRETATION

Our study revealed that the post-BA.2/5 subvariants are attenuated in lungs while increased in replication fitness in the nasal epithelium, indicating rapid adaptation of the circulating Omicron subvariants in the human populations.

FUNDING

The full list of funding can be found at the Acknowledgements section.

Characteristics and Presentations of Hospitalized Children Due to 3 Predominate COVID-19 Variants Within a Health Care Network

Objective of this article is to describe differences in the demographic and clinical characteristics, severity of illness, and outcomes in pediatric patients with different SARS-CoV-2 variants. We conducted a retrospective study of pediatric patients admitted with COVID-19 during the 3 large waves of infection within a health network in New Jersey. We included demographic characteristics, clinical features, and outcomes and compared the data with respect to the different variants. Of 351 total patients included in this study, 74 were admitted during wave 1, 94 during wave 2, and 181 during wave 3. The median age of patients decreased from wave 1 (11.5 years) to wave 3 (3 years) (P = .0034). 87.7% of the patients were unvaccinated. The overall incidence of admissions due to pneumonia related to COVID-19 decreased in wave 3. COVID-19 bronchiolitis or croup admissions occurred mostly in wave 3. There was no significant difference in the number of patients requiring intensive care in any particular wave. Length of stay decreased across the waves (P < .0001). Treatments required did not vary between the waves except for a decrease in antibiotic use with each subsequent wave (P < .0001). The impact of COVID-19 on the pediatric population differs from the adult population, and the overall number of hospitalized children has mirrored the peak in cases observed during each infection wave. Our study illustrates the changes in clinical presentation and severity observed with the different coronavirus variants.

Effectiveness of the pre-Omicron COVID-19 vaccines against Omicron in reducing infection, hospitalization, severity, and mortality compared to Delta and other variants: A systematic review

Despite widespread mass rollout programs, the rapid spread of the SARS-CoV-2 Omicron variant called into question the effectiveness of the existing vaccines against infection, hospitalization, severity, and mortality compared to previous variants. This systematic review summarizes and compares the effectiveness of the COVID-19 vaccines, with respect to the above outcomes in adults, children, and adolescents. A comprehensive literature search was undertaken on several databases. Only 51 studies met our inclusion criteria, revealing that the protection from primary vaccination against Omicron infection is inferior to protection against Delta and Alpha infections and wanes faster over time. However, mRNA vaccine boosters were reported to reestablish effectiveness, although to a lower extent against Omicron. Nonetheless, primary vaccination was shown to preserve strong protection against Omicron-associated hospitalization, severity, and death, even months after last dose. However, boosters provide more robust and longer-lasting protection against hospitalizations due to Omicron as compared to only primary series.

COVID-19 in Patients with Melanoma: A Single-Institution Study

We conducted a single-center, non-interventional retrospective study of melanoma patients with COVID-19 (1 March 2020 until 17 March 2023). The cohort was further divided into three groups according to the periods of SARS-CoV-2 variant dominance in Greece. We recorded demographics, comorbidities, vaccination data, cancer diagnosis/stage, types of systemic melanoma treatments, date of COVID-19 diagnosis and survival. We identified 121 patients. The vast majority (87.6%) had advanced disease (stages III or IV). A total of 80.1% of the patients were receiving immune checkpoint inhibitor-based therapies, 92.5% had asymptomatic/mild COVID-19 and 7.4% had moderate/severe/critical disease, while 83.5% contracted COVID-19 during the third period of the pandemic. Sixteen patients (13.2%) were hospitalized for COVID-19 with a median length of stay of 12 days (range: 1-55 days). Advanced age, heart failure, number of comorbidities (≤1 vs. >1), vaccination status and the time period of the infection correlated with more severe COVID-19, whereas only heart failure and time period were independently correlated with severity. The 30-day mortality rate after COVID-19 was 4.2%. With a median follow-up of 340 days post-COVID-19, 17.4% of patients were deceased. In this cohort of melanoma patients with COVID-19, the 30-day mortality rate was low. There was no association between melanoma stage, treatment receipt and type of treatment with COVID-19 severity.

The domestication of SARS-CoV-2 into a seasonal infection by viral variants

Introduction

The COVID-19 pandemic was caused by the zoonotic betacoronavirus SARS-CoV-2. SARS-CoV-2 variants have emerged due to adaptation in humans, shifting SARS-CoV-2 towards an endemic seasonal virus. We have termed this process 'virus domestication'.

Methods

We analyzed aggregate COVID-19 data from a publicly funded healthcare system in Canada from March 7, 2020 to November 21, 2022. We graphed surrogate calculations of COVID-19 disease severity and SARS-CoV-2 variant plaque sizes in tissue culture.

Results and Discussion

Mutations in SARS-CoV-2 adapt the virus to better infect humans and evade the host immune response, resulting in the emergence of variants with altered pathogenicity. We observed a decrease in COVID-19 disease severity surrogates after the arrival of the Delta variant, coinciding with significantly smaller plaque sizes. Overall, we suggest that SARS-CoV-2 has become more infectious and less virulent through viral domestication. Our findings highlight the importance of SARS-CoV-2 vaccination and help inform public policy on the highest probability outcomes during viral pandemics.

Virological Characteristics of Five SARS-CoV-2 Variants, Including Beta, Delta and Omicron BA.1, BA.2, BA.5

SARS-CoV-2 variants of concern (VOCs) show increasing transmissibility and infectivity and induce substantial injuries to human health and the ecology. Therefore, it is vital to understand the related features for controlling infection. In this study, SARS-CoV-2 WIV04 (prototype) and five VOCs (Beta, Delta, Omicron BA.1, BA.2 and BA.5 variants) were inoculated in Vero cells to observe their growth activities. Apart from evaluating the environmental stability at different temperatures, residual virus titers and infectivity at different temperatures (4 °C, room temperature (RT) and 37 °C) were measured over 7 days. The experiment also assessed the infectivity for different incubation durations. The growth capacity assay suggested that the WIV04, Beta and Delta variants replicated efficiently in Vero cells compared with Omicron Variants, and BA.2 replicated more efficiently in Vero cells than BA.1 and BA.5. In addition, all variants exhibited longer survivals at 4 °C and could remain infectious after 7 days, compared to RT' survival after 5 days and at 37 °C after 1 day. The virus infection assay indicated that the Omicron variant had a weaker ability to infect cells compared to the WIV04, Beta and Delta strains, and a longer infection time was required for these strains, except for BA.2.

Characteristics and outcomes of patients hospitalized for infection with influenza, SARS-CoV-2 or respiratory syncytial virus in the season 2022/2023 in a large German primary care centre

BACKGROUND

In 2022/2023, Influenza A and Respiratory Syncytial Virus (RSV) reappeared in hospitalized patients, which was in parallel to ongoing SARS-CoV-2 infections. The aim of our study was to compare the characteristics and outcomes of these infections during the same time.

METHODS

We included patients of all ages with a positive polymerase chain reaction (PCR) test for Influenza A/B, RSV, or SARS-CoV-2 virus hospitalized in the neurological, internal or paediatric units of the RoMed Hospital Rosenheim, Germany, between October 1st 2022 and February 28th 2023.

RESULTS

A total of 906 patients were included (45.6% female; median age 68.0 years; 21.9% Influenza A, 48.2% SARS-CoV-2, 28.3% RSV). Influenza B (0.2%) and co-infections (1.5%) played a minor role. In patients aged ≥ 18 years (n = 637, 71%), Influenza A, SARS-CoV-2 and RSV groups differed in age (median 72, 79, 76 years, respectively; p < 0.001). Comorbidities, particularly asthma and COPD, were most prevalent for RSV. 103 patients were admitted to the intensive care unit (ICU) (16.3% Influenza A, 15.3% SARS-CoV-2, 19.2% RSV; p = 0.649), 56 died (6.8% Influenza A, 9% SARS-CoV-2, 11.1% RSV; p = 0.496). RSV showed the highest frequencies of low-flow oxygen supplementation for admission and stay. Differences in the length of stay were minor (median 7 days). Conversely, in patients aged < 18 years (n = 261, 28,8%), 19.5%, 17.6% and 60.2% were in the Influenza A, SARS-CoV-2 and RSV groups, respectively; 0.4% showed Influenza B and 2.3% co-infections. 17 patients were admitted to ICU (3.9% Influenza A, 9.6% RSV, 0% SARS-CoV-2); none died. RSV showed the highest frequencies of high- and low-flow oxygen supplementation, SARS-CoV-2 the lowest.

CONCLUSION

When comparing infections with Influenza, SARS-CoV-2 and RSV in the winter 2022/2023 in hospitalized adult patients, rates of ICU admission and mortality were similar. RSV showed the highest frequencies of obstructive airway diseases, and of oxygen supplementation. The latter was also true in children/adolescents, in whom RSV dominated. Thus, in the situation of declining importance of SARS-CoV-2, RSV showed a disease burden that was relatively higher than that from Influenza and SARS-CoV-2 across ages, and this might be relevant for the seasons coming.

Innovation-driven trend shaping COVID-19 vaccine development in China

Confronted with the Coronavirus disease 2019 (COVID-19) pandemic, China has become an asset in tackling the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission and mutation, with several innovative platforms, which provides various technical means in this persisting combat. Derived from collaborated researches, vaccines based on the spike protein of SARS-CoV-2 or inactivated whole virus are a cornerstone of the public health response to COVID-19. Herein, we outline representative vaccines in multiple routes, while the merits and plights of the existing vaccine strategies are also summarized. Likewise, new technologies may provide more potent or broader immunity and will contribute to fight against hypermutated SARS-CoV-2 variants. All in all, with the ultimate aim of delivering robust and durable protection that is resilient to emerging infectious disease, alongside the traditional routes, the discovery of innovative approach to developing effective vaccines based on virus properties remains our top priority.

Persisting symptoms common but inability to work rare: a one-year follow-up study of Finnish hospitalised COVID-19 patients

BACKGROUND

Difficulties in recovery persisting for months have been reported in patients with severe COVID-19. Our aim was to investigate respiratory and overall recovery one year after hospital discharge.

METHODS

Finnish patients hospitalised due to COVID-19 during the first wave of the pandemic were recruited to a survey of symptoms, quality of life (RAND-36), work status, and health care use one year after hospital discharge. Patients with lung function test and chest x-ray results available from 3-6 months after hospital discharge underwent spirometry and a chest x-ray at one year.

RESULTS

Ninety-six patients responded to the one-year survey, 32 underwent spirometry and 32 a chest x-ray. Of those working full-time before COVID-19, median duration of sick leave was 40 days and 10% had not returned to work at one year. Health-care service use related to COVID-19 after discharge was reported by 79%, 50% using primary care, 34% occupational health care and 32% specialist care, respectively. Tiredness, fatigue, and physical difficulties increased in follow-up (p = 0.022-0.033). Quality of life did not change. Chest x-ray abnormalities decreased in follow-up, with an abnormal chest x-ray in 58% at 3-6 months and 25% at one year. A restrictive spirometry pattern was more common at one year (16 vs. 34%, p = 0.014).

CONCLUSIONS

Prolonged symptoms are common, some patients have decreased lung function, and a small minority of patients still have not returned to work one year after severe COVID-19. This calls for further research into the underlying causes and risk factors for prolonged recovery.

Evaluation of the US COVID-19 Scenario Modeling Hub for informing pandemic response under uncertainty

Our ability to forecast epidemics far into the future is constrained by the many complexities of disease systems. Realistic longer-term projections may, however, be possible under well-defined scenarios that specify the future state of critical epidemic drivers. Since December 2020, the U.S. COVID-19 Scenario Modeling Hub (SMH) has convened multiple modeling teams to make months ahead projections of SARS-CoV-2 burden, totaling nearly 1.8 million national and state-level projections. Here, we find SMH performance varied widely as a function of both scenario validity and model calibration. We show scenarios remained close to reality for 22 weeks on average before the arrival of unanticipated SARS-CoV-2 variants invalidated key assumptions. An ensemble of participating models that preserved variation between models (using the linear opinion pool method) was consistently more reliable than any single model in periods of valid scenario assumptions, while projection interval coverage was near target levels. SMH projections were used to guide pandemic response, illustrating the value of collaborative hubs for longer-term scenario projections.

Habitual Mask Wearing as Part of COVID-19 Control in Japan: An Assessment Using the Self-Report Habit Index

Although the Japanese government removed mask-wearing requirements in 2023, relatively high rates of mask wearing have continued in Japan. We aimed to assess psychological reasons and the strength of habitual mask wearing in Japan. An Internet-based cross-sectional survey was conducted with non-random participant recruitment. We explored the frequency of mask usage, investigating psychological reasons for wearing masks. A regression analysis examined the association between psychological reasons and the frequency of mask wearing. The habitual use of masks was assessed in the participant's most frequently visited indoor space and public transport using the self-report habit index. The principal component analysis with varimax rotation revealed distinct habitual characteristics. Among the 2640 participants surveyed from 6 to 9 February 2023, only 4.9% reported not wearing masks at all. Conformity to social norms was the most important reason for masks. Participants exhibited a slightly higher degree of habituation towards mask wearing on public transport compared to indoor spaces. The mask-wearing rate was higher in females than in males, and no significant difference was identified by age group. Daily mask wearing in indoor spaces was characterized by two traits (automaticity and behavioral frequency). A high mask-wearing frequency has been maintained in Japan during the social reopening transition period. Mask wearing has become a part of daily habit, especially on public transport, largely driven by automatic and frequent practice.