Decreased severity of the Omicron variant of concern: further evidence from Italy

Diverse pro-inflammatory ability of mutated spike protein derived from variant strains of SARS-CoV-2

The severity of COVID-19 has been reported to differ among SARS-CoV-2 mutant variants. The overactivation of macrophages is involved in severe COVID-19, yet the effects of SARS-CoV-2 mutations on macrophages remain poorly understood. To clarify the effects, we examined whether mutations of spike proteins (S-proteins) affect macrophage activation. CD14+ monocyte-derived macrophages were stimulated with the recombinant S-protein of the wild-type, Delta, and Omicron strains or live viral particles of individual strains. Regarding IL-6 and TNF-α, Delta or Omicron S-protein had stronger or weaker pro‑inflammatory ability, respectively, than the wild-type. Similar trends were observed between S-proteins and viral particles. S-protein mutations could be related to the diversity in macrophage activation and severity rates in COVID-19 caused by various SARS-CoV-2 strains.

Multidimensional analysis of immune cells from COVID-19 patients identified cell subsets associated with the severity at hospital admission

BACKGROUND

SARS-CoV-2 emerged as a new coronavirus causing COVID-19, and it has been responsible for more than 760 million cases and 6.8 million deaths worldwide until March 2023. Although infected individuals could be asymptomatic, other patients presented heterogeneity and a wide range of symptoms. Therefore, identifying those infected individuals and being able to classify them according to their expected severity could help target health efforts more effectively.

METHODOLOGY/PRINCIPAL FINDINGS

Therefore, we wanted to develop a machine learning model to predict those who will develop severe disease at the moment of hospital admission. We recruited 75 individuals and analysed innate and adaptive immune system subsets by flow cytometry. Also, we collected clinical and biochemical information. The objective of the study was to leverage machine learning techniques to identify clinical features associated with disease severity progression. Additionally, the study sought to elucidate the specific cellular subsets involved in the disease following the onset of symptoms. Among the several machine learning models tested, we found that the Elastic Net model was the better to predict the severity score according to a modified WHO classification. This model was able to predict the severity score of 72 out of 75 individuals. Besides, all the machine learning models revealed that CD38+ Treg and CD16+ CD56neg HLA-DR+ NK cells were highly correlated with the severity.

CONCLUSIONS/SIGNIFICANCE

The Elastic Net model could stratify the uninfected individuals and the COVID-19 patients from asymptomatic to severe COVID-19 patients. On the other hand, these cellular subsets presented here could help to understand better the induction and progression of the symptoms in COVID-19 individuals.

Long-Term Trajectory and Risk Factors of Healthcare Workers' Mental Health during COVID-19 Pandemic: A 24 Month Longitudinal Cohort Study

BACKGROUND

Research has shown the substantial impact of the COVID-19 pandemic on healthcare workers' (HCWs) mental health, however, it mostly relies on data collected during the early stages of COVID-19. The aim of this study is to assess the long-term trajectory of HCWs' mental health and the associated risk factors.

METHODS

a longitudinal cohort study was carried out in an Italian hospital. At Time 1 (July 2020-July 2021), 990 HCWs took part in the study and completed the General Health Questionnaire (GHQ-12), the Impact of Event Scale (IES-R), and the General Anxiety Disorder (GAD-7)questionnaire. McNemar's test measured changes in symptoms' trajectories, and random effects models evaluated risk factors associated with scores above the cut-off.

RESULTS

310 HCWs participated to the follow-up evaluation (Time 2; July 2021-July 2022). At Time 2, scores above cut-offs were significantly lower (p < 0.001) than at Time 1 for all scales (23% vs. 48% for GHQ-12; 11% vs. 25% for IES-R; 15% vs. 23% for GAD-7). Risk factors for psychological impairment were being a nurse (IES-R: OR 4.72, 95% CI 1.71-13.0; GAD-7: OR 2.82, 95% CI 1.44-7.17), a health assistant (IES-R: OR 6.76, 95% CI 1.30-35.1), or having had an infected family member (GHQ-12: OR 1.95, 95% CI 1.01-3.83). Compared to Time 1, gender and experience in COVID-19 units lost significance with psychological symptoms.

CONCLUSIONS

data over more than 24 months from the pandemic onset showed improvement of HCWs' mental health; our findings suggested the need to tailor and prioritize preventive actions towards healthcare workforce.

Reduction in severity and mortality in COVID-19 patients owing to heterologous third and fourth-dose vaccines during the periods of delta and omicron predominance in Thailand

OBJECTIVES

The COVID-19 pandemic has evolved quickly, with different variants of concern resulting in the need for countries to offer booster vaccinations. Although studies have assessed homologous schedules in detail, the effectiveness of heterologous booster vaccine schedules against severity and mortality with newer variants remains to be explored fully.

METHODS

Utilizing a Hospital Information System for COVID-19 established in Chiang Mai, Thailand, we conducted a cohort study by linking patient-level data on laboratory-confirmed COVID-19 cases to the national immunization records, during delta-predominant and omicron-predominant periods.

RESULTS

Compared to omicron, COVID-19 cases during the delta period were 10 times more likely to have severe outcomes and in-hospital deaths. During omicron, a third vaccine dose had an 89% reduced risk of both severe COVID-19 and death. The third dose received 14-90 days before the date of the positive test showed the highest protection (93%). Severe outcomes were not observed with the third dose during delta, and the fourth dose during the omicron period. All the vaccine types used for boosting in Thailand offered similar protection against severe COVID-19.

CONCLUSION

Booster doses provided a very high level of protection against severe COVID-19 outcomes and deaths. Booster campaigns should focus on improving coverage by utilizing all available vaccines to ensure optimal protection.

A comparative study of spike protein of SARS-CoV-2 and its variant Omicron (B.1.1.529) on some immune characteristics

The emergence of Omicron variant raises great concerns because of its rapid transmissibility and its numerous mutations in spike protein (S-protein). S-protein can act as a pathogen-associated molecular pattern and complement activator as well as antigen. We compared some immune characteristics of trimer S-proteins for wild type (WT-S) and B.1.1.529 Omicron (Omicron-S) to investigate whether the mutations have affected its pathogenicity and antigenic shift. The results indicated that WT-S and Omicron-S directly activated nuclear factor-κB (NF-κB) and induced the release of pro-inflammatory cytokines in macrophages, but the actions of Omicron-S were weaker. These inflammatory reactions could be abrogated by a Toll-like receptor 4 antagonist TAK-242. Two S-proteins failed to induce the production of antiviral molecular interferon-β. In contrast to pro-inflammatory effects, the ability of two S-proteins to activate complement was comparable. We also compared the binding ability of two S-proteins to a high-titer anti-WT-receptor-binding domain antibody. The data showed that WT-S strongly bound to this antibody, while Omicron-S was completely off-target. Collectively, the mutations of Omicron have a great impact on the pro-inflammatory ability and epitopes of S-protein, but little effect on its ability to activate complement. Addressing these issues can be helpful for more adequate understanding of the pathogenicity of Omicron and the vaccine breakthrough infection.

A Comparison Between Omicron and Earlier COVID-19 Variants' Disease Severity in the Milan Area, Italy

Background

In the context of the fourth wave of the COVID-19 pandemic in Italy, which occurred in correspondence with the outbreak of the Omicron variant, it became fundamental to assess differences in the risk of severe disease between the Omicron variant and the earlier SARS-CoV-2 variants that were still in circulation despite Omicron becoming prevalent.

Methods

We collected data on 2,267 genotyped PCR-positive swab tests and assessed whether the presence of symptoms, risk of hospitalization, and recovery times were significantly different between Omicron and the earlier variants. Multivariable models adjusted for sex, age class, citizenship, comorbidities, and symptomatology allowed assessing the difference in outcomes between Omicron and the earlier variants according to vaccination status and timing of administration.

Results

Compared to the earlier variants in the same period, Omicron was less symptomatic, resulted in fewer hospital admissions for those who were unvaccinated and for those who were already immunized after the booster dose, and was associated with quicker recovery, yet not in subjects with three vaccination doses.

Conclusion

Despite being milder, Omicron's higher transmissibility and vaccine resistance should not lead to underrating its damage potential, especially with regard to hospital and health service saturation.