What do we know about SARS-CoV-2 transmission? A systematic review and meta-analysis of the secondary attack rate and associated risk factors

Susceptibility and infectiousness of SARS-CoV-2 in children versus adults, by variant (wild-type, alpha, delta): A systematic review and meta-analysis of household contact studies

IMPORTANCE

Understanding the susceptibility and infectiousness of children and adolescents in comparison to adults is important to appreciate their role in the COVID-19 pandemic.

OBJECTIVE

To determine SARS-CoV-2 susceptibility and infectiousness of children and adolescents with adults as comparator for three variants (wild-type, alpha, delta) in the household setting. We aimed to identify the effects independent of vaccination or prior infection.

DATA SOURCES

We searched EMBASE, PubMed and medRxiv up to January 2022.

STUDY SELECTION

Two reviewers independently identified studies providing secondary household attack rates (SAR) for SARS-CoV-2 infection in children (0-9 years), adolescents (10-19 years) or both compared with adults (20 years and older).

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently extracted data, assessed risk of bias and performed a random-effects meta-analysis model.

MAIN OUTCOMES AND MEASURES

Odds ratio (OR) for SARS-CoV-2 infection comparing children and adolescents with adults stratified by wild-type (ancestral type), alpha, and delta variant, respectively. Susceptibility was defined as the secondary attack rate (SAR) among susceptible household contacts irrespective of the age of the index case. Infectiousness was defined as the SAR irrespective of the age of household contacts when children/adolescents/adults were the index case.

RESULTS

Susceptibility analysis: We included 27 studies (308,681 contacts), for delta only one (large) study was available. Compared to adults, children and adolescents were less susceptible to the wild-type and delta, but equally susceptible to alpha. Infectiousness analysis: We included 21 studies (201,199 index cases). Compared to adults, children and adolescents were less infectious when infected with the wild-type and delta. Alpha -related infectiousness remained unclear, 0-9 year old children were at least as infectious as adults. Overall SAR among household contacts varied between the variants.

CONCLUSIONS AND RELEVANCE

When considering the potential role of children and adolescents, variant-specific susceptibility, infectiousness, age group and overall transmissibility need to be assessed.

Seroprevalence of SARS-CoV-2 in self-reported COVID-19-free children

INTRODUCTION

COVID-19 poses risks and leads to complications for vulnerable populations, including children. Unreported cases of COVID-19 among children hinder our understanding of the true disease burden. In this study, we aimed to investigate the proportion of children who report no prior infection to SARS-CoV-2 but who nevertheless exhibit serological evidence of prior infection.

METHODS

Between November 2022 and February 2023, we recruited children and adolescents under 19 years of age who lacked a prior history of SARS-CoV-2 infection. Participants underwent SARS-CoV-2 antibody testing to assess the presence of IgG antibodies specific to nucleocapsid (N) and spike (S) proteins. Demographic and contact information were also collected.

RESULTS

Among 260 COVID-19-free children, the overall anti-N antibody positivity rate, which varied across age groups (4%-25%), was 9.2% (24/260). Contact with individuals who were positive for COVID-19, particularly the children's mothers, significantly increased the likelihood of antibody positivity. The median age of the 34 children who remained unvaccinated against COVID-19 was lower than that of the children who were vaccinated (6.5 vs. 9 years; p < 0.001). Until January 2024, the overall infection rate was 41.9% (99/236) among children who were negative for anti-N antibodies, irrespective of vaccination status or the presence of chronic disease.

CONCLUSION

We discovered previously undisclosed cases of SARS-CoV-2 infection among children. The risk of seropositivity increases substantially with household contact. Regarding children who report no prior exposure to COVID-19, clinicians must remain vigilant, as SARS-CoV-2 remains a concern.

A prospective randomised controlled trial investigating household SARS-CoV-2 transmission in a densely populated community in Cape Town, South Africa - the transmission of COVID-19 in crowded environments (TRACE) study

BACKGROUND

South Africa's first SARS-CoV-2 case was identified 5th March 2020 and national lockdown followed March 26th. Households are an important location for secondary SARS-CoV-2 infection. Physical distancing and sanitation - infection mitigation recommended by the World Health Organization (WHO) at the time - are difficult to implement in limited-resource settings because of overcrowded living conditions.

METHODS

This study (ClinicalTrials.gov NCT05119348) was conducted from August 2020 to September 2021 in two densely populated, low socioeconomic Cape Town community sub-districts. New COVID-19 index cases (ICs) identified at public clinics were randomised to an infection mitigation intervention (STOPCOV) delivered by lay community health workers (CHWs) or standard of care group. STOPCOV mitigation measures included one initial household assessment conducted by a CHW in which face masks, sanitiser, bleach and written information on managing and preventing spread were provided. This was followed by regular telephonic follow-up from CHWs. SARS-CoV-2 PCR and IgM/IgG serology was performed at baseline, weeks 1, 2, 3 and 4 of follow-up.

RESULTS

The study randomised 81 ICs with 245 HHCs. At baseline, no HHCs in the control and 7 (5%) in the intervention group had prevalent SARS-CoV-2. The secondary infection rate (SIR) based on SARS-CoV-2 PCR testing was 1.9% (n = 2) in control and 2.9% (n = 4) in intervention HHCs (p = 0.598). At baseline, SARS-CoV-2 antibodies were present in 15% (16/108) of control and 38% (52/137) of intervention participants. At study end incidence was 8.3% (9/108) and 8.03% (11/137) in the intervention and control groups respectively. Antibodies were present in 23% (25/108) of control HHCs over the course of the study vs. 46% (63/137) in the intervention arm. CHWs made twelve clinic and 47 food parcel referrals for individuals in intervention households in need.

DISCUSSION

Participants had significant exposure to SARS-CoV-2 infections prior to the study. In this setting, household transmission mitigation was ineffective. However, CHWs may have facilitated other important healthcare and social referrals.

Detecting and quantifying heterogeneity in susceptibility using contact tracing data

The presence of heterogeneity in susceptibility, differences between hosts in their likelihood of becoming infected, can fundamentally alter disease dynamics and public health responses, for example, by changing the final epidemic size, the duration of an epidemic, and even the vaccination threshold required to achieve herd immunity. Yet, heterogeneity in susceptibility is notoriously difficult to detect and measure, especially early in an epidemic. Here we develop a method that can be used to detect and estimate heterogeneity in susceptibility given contact by using contact tracing data, which are typically collected early in the course of an outbreak. This approach provides the capability, given sufficient data, to estimate and account for the effects of this heterogeneity before they become apparent during an epidemic. It additionally provides the capability to analyze the wealth of contact tracing data available for previous epidemics and estimate heterogeneity in susceptibility for disease systems in which it has never been estimated previously. The premise of our approach is that highly susceptible individuals become infected more often than less susceptible individuals, and so individuals not infected after appearing in contact networks should be less susceptible than average. This change in susceptibility can be detected and quantified when individuals show up in a second contact network after not being infected in the first. To develop our method, we simulated contact tracing data from artificial populations with known levels of heterogeneity in susceptibility according to underlying discrete or continuous distributions of susceptibilities. We analyzed these data to determine the parameter space under which we are able to detect heterogeneity and the accuracy with which we are able to estimate it. We found that our power to detect heterogeneity increases with larger sample sizes, greater heterogeneity, and intermediate fractions of contacts becoming infected in the discrete case or greater fractions of contacts becoming infected in the continuous case. We also found that we are able to reliably estimate heterogeneity and disease dynamics. Ultimately, this means that contact tracing data alone are sufficient to detect and quantify heterogeneity in susceptibility.

What is the specific role of schools and daycares in COVID-19 transmission? A final report from a living rapid review

Due to rapidly evolving conditions, the question of how to safely operate schools and daycares remained a top priority throughout the COVID-19 pandemic. In response to growing and changing evidence, the National Collaborating Centre for Methods and Tools in Canada maintained a living rapid review on the role of schools and daycares in COVID-19 transmission to guide evidence-informed decision making. This Review presents the final iteration of this living rapid review. 31 sources were searched until Oct 17, 2022. In the final version, eligible studies reported data from Jan 1, 2021 onward on transmission of COVID-19 in school or daycare settings, the effect of infection prevention and control measures on transmission, or the effect of operating schools or daycares on community-level COVID-19 rates. As a rapid review, titles and abstracts were screened by a single reviewer with artificial intelligence integrated into later versions. Full-text screening, data extraction, and critical appraisal were completed by one reviewer and checked by a second reviewer. The Johanna Briggs Institute tools were used for critical appraisal. The certainty of evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation approach, and results were synthesised narratively. Three citizen partners provided input for the final interpretation. This final update includes 73 primary studies. Secondary attack rates were low within school settings when infection prevention and control measures were in place (moderate certainty). Masks might reduce transmission, test-to-stay policies might not increase transmission risk compared with mandatory quarantine, cohorting and hybrid learning might make little to no difference in transmission (low certainty), and the effect of surveillance testing within schools remained inconclusive (very low certainty). Findings indicate that school settings do not substantially contribute to community incidence, hospitalisations, or mortality (low certainty). This living review provides a synthesis of global evidence for the role of schools and daycares during COVID-19, which might be helpful in future pandemics.

Household secondary attack rate amongst the susceptible contacts of COVID-19 cases and its epidemiological profile: A retrospective study from central Gujarat, India

Introduction

Secondary attack rate (SAR) is a proportion of primary contacts developing the diseases within the incubation period upon exposure to a primary case among the total susceptible household contacts. The epidemiological profile and SAR will help in understanding the transmission dynamics of COVID-19 for further strengthening preventive and effective control measures.

Objectives of the Study

The study was conducted with the primary objective to estimate the household SAR of COVID-19 cases at Mahisagar District, Gujarat, and to study the epidemiological profile of primary and secondary cases of COVID-19.

Methodology

A retrospective study was conducted to estimate SAR among 245 confirmed cases of COVID-19 and 898 susceptible household contacts in Mahisagar district through telephonic interview and questionnaire by the Investigator team.

Results

The household SAR was calculated from the current study in Mahisagar district, Gujarat, and was 13.9%. Among primary cases, 74.7% males were affected, and among secondary cases, 52.8% females were affected. The SAR among elderly was 23.9%, and the SAR among children was 3.9%. 74.1% household contacts had developed disease among symptomatic contacts as compared to asymptomatic household contacts.

Conclusion

The household SAR in Mahisagar district, Gujarat, was found to be 13.9%. In primary cases, more males, and in secondary cases, more females were found to be affected. The household SAR was increased in elderly as compared to the younger age group. The SAR was more among the contacts of symptomatic cases than asymptomatic cases. Overall hospitalization in public hospitals was more than that in private hospitals.

Overestimation of Severe Acute Respiratory Syndrome Coronavirus 2 Household Transmission in Settings of High Community Transmission: Insights From an Informal Settlement Community in Salvador, Brazil

Background

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant has spread globally. However, the contribution of community versus household transmission to the overall risk of infection remains unclear.

Methods

Between November 2021 and March 2022, we conducted an active case-finding study in an urban informal settlement with biweekly visits across 1174 households with 3364 residents. Individuals displaying coronavirus disease 2019 (COVID-19)-related symptoms were identified, interviewed along with household contacts, and defined as index and secondary cases based on reverse-transcription polymerase chain reaction (RT-PCR) and symptom onset.

Results

In 61 households, we detected a total of 94 RT-PCR-positive cases. Of 69 sequenced samples, 67 cases (97.1%) were attributed to the Omicron BA.1* variant. Among 35 of their households, the secondary attack rate was 50.0% (95% confidence interval [CI], 37.0%-63.0%). Women (relative risk [RR], 1.6 [95% CI, .9-2.7]), older individuals (median difference, 15 [95% CI, 2-21] years), and those reporting symptoms (RR, 1.73 [95% CI, 1.0-3.0]) had a significantly increased risk for SARS-CoV-2 secondary infection. Genomic analysis revealed substantial acquisition of viruses from the community even among households with other SARS-CoV-2 infections. After excluding community acquisition, we estimated a household secondary attack rate of 24.2% (95% CI, 11.9%-40.9%).

Conclusions

These findings underscore the ongoing risk of community acquisition of SARS-CoV-2 among households with current infections. The observed high attack rate necessitates swift booster vaccination, rapid testing availability, and therapeutic options to mitigate the severe outcomes of COVID-19.

Optimal social distancing in epidemic control: cost prioritization, adherence and insights into preparedness principles

The COVID-19 pandemic experience has highlighted the importance of developing general control principles to inform future pandemic preparedness based on the tension between the different control options, ranging from elimination to mitigation, and related costs. Similarly, during the COVID-19 pandemic, social distancing has been confirmed to be the critical response tool until vaccines become available. Open-loop optimal control of a transmission model for COVID-19 in one of its most aggressive outbreaks is used to identify the best social distancing policies aimed at balancing the direct epidemiological costs of a threatening epidemic with its indirect (i.e., societal level) costs arising from enduring control measures. In particular, we analyse how optimal social distancing varies according to three key policy factors, namely, the degree of prioritization of indirect costs, the adherence to control measures, and the timeliness of intervention. As the prioritization of indirect costs increases, (i) the corresponding optimal distancing policy suddenly switches from elimination to suppression and, finally, to mitigation; (ii) the "effective" mitigation region-where hospitals' overwhelming is prevented-is dramatically narrow and shows multiple control waves; and (iii) a delicate balance emerges, whereby low adherence and lack of timeliness inevitably force ineffective mitigation as the only accessible policy option. The present results show the importance of open-loop optimal control, which is traditionally absent in public health preparedness, for studying the suppression-mitigation trade-off and supplying robust preparedness guidelines.

Personal protective measures and settings on the risk of SARS-COV-2 community transmission: a case-control study

Background

During the SARS-CoV-2 pandemic, nurses of primary health care has been an important role in Spain. Even so, the data obtained in the tracing have been scarcely used to investigate the possible mechanisms of transmission. Few studies focused on community transmission, evaluating the effectiveness of individual protective measures and exposure environment. The main aim of the study was to evaluate the association between individual protective measures and SARS-CoV-2 transmission in the community and to compare secondary attack rates in different exposure settings.

Methods

A case-control study from contact tracing of SARS-CoV-2 index patients. COVID-19 contact tracing was led by nurses at the COVID-19 Coordinating Centre in Majorca (Spain). During the systematic tracing, additional information for this study was collected from the index patient (social-demographic variables, symptoms, the number of close contacts). And also, the following variables from their close contacts: contact place, ventilation characteristics mask-wearing, type of mask, duration of contact, shortest distance, case-contact relationship, household members, and handwashing, the test result for SARS-CoV-2 diagnostic. Close contacts with a positive test for SARS-CoV-2 were classified as "cases" and those negative as "controls."

Results

A total of 1,778 close contacts from 463 index patients were identified. No significant differences were observed between the sexes but between age groups. Overall Secondary Attack Rate (SAR) was 24.0% (95% CI: 22.0-26.0%), 36.9% (95% CI: 33.2-40.6%) in closed spaces without ventilation and 50.7% (95% CI: 45.6-55.8%) in exposure time > 24 h. A total of 49.2% of infections occurred among household members. Multivariate logistic regression analysis showed that open-air setting (OR 0.43, 95% CI: 0.27-0.71), exposure for less than 1 h (OR 0.19, 95% CI: 0.11-0.32), and wearing a mask (OR 0.49, 95% CI: 0.28-0.85) had a protective effect transmission of SARS-CoV-2 in the community.

Conclusion

Ventilation of the space, mask-wearing and shorter exposure time were associated with a lower risk of transmission in the community. The data obtained allowed an assessment of community transmission mechanisms and could have helped to improve and streamline tracing by identifying close contacts at higher risk.

Social determinants of ethnic disparities in SARS-CoV-2 infection: UK Biobank SARS-CoV-2 Serology Study

BACKGROUND

The social determinants of ethnic disparities in risk of SARS-CoV-2 infection during the first wave of the pandemic in the UK remain unclear.

METHODS

In May 2020, a total of 20 195 adults were recruited from the general population into the UK Biobank SARS-CoV-2 Serology Study. Between mid-May and mid-November 2020, participants provided monthly blood samples. At the end of the study, participants completed a questionnaire on social factors during different periods of the pandemic. Logistic regression yielded ORs for the association between ethnicity and SARS-CoV-2 immunoglobulin G antibodies (indicating prior infection) using blood samples collected in July 2020, immediately after the first wave.

RESULTS

After exclusions, 14 571 participants (mean age 56; 58% women) returned a blood sample in July, of whom 997 (7%) had SARS-CoV-2 antibodies. Seropositivity was strongly related to ethnicity: compared with those of White ethnicity, ORs (adjusted for age and sex) for Black, South Asian, Chinese, Mixed and Other ethnic groups were 2.66 (95% CI 1.94-3.60), 1.66 (1.15-2.34), 0.99 (0.42-1.99), 1.42 (1.03-1.91) and 1.79 (1.27-2.47), respectively. Additional adjustment for social factors reduced the overall likelihood ratio statistics for ethnicity by two-thirds (67%; mostly from occupational factors and UK region of residence); more precise measurement of social factors may have further reduced the association.

CONCLUSIONS

This study identifies social factors that are likely to account for much of the ethnic disparities in SARS-CoV-2 infection during the first wave in the UK, and highlights the particular relevance of occupation and residential region in the pathway between ethnicity and SARS-CoV-2 infection.

Trends in the numbers of SARS-CoV-2 infections among students: a prospective cohort study comparing students in sports boarding schools with students in day schools during early COVID-19 pandemic

Introduction

During the first months of the COVID pandemic it emerged that facilities where people gather or live together in cohorts, such as nursing homes or schools, were particularly at high risk for becoming hotspots of virus transmission. German political and health institutions responded with far-reaching interventions and preventive strategies to protect the population from infection with SARS-CoV-2. In this context, it remains unclear whether boarding schools for sports particularly pose a risk of infection to their residents.

Methods

In a single-center prospective cohort study, numbers of SARS-CoV-2 infections of students in sports boarding schools (n = 11) vs. students attending regular day schools (n = 22) in the region Freiburg/Hochschwarzwald in Germany were investigated over a period from October 2020 to January 2021 via regular virus and antibody screening (German Clinical Trials Register; Study ID: DRKS00021909). In addition, individual and behavioral risk factors for infection were stratified via questionnaire, which provide an indication of cohort specific risk factors for infection and the success of the implementation of hygiene concepts, as well as other infection prevention strategies, within the respective facilities.

Results

Regarding SARS-CoV-2 infection numbers, the screening detected no significant group difference between sports boarding schools vs. day schools.

Discussion

The study results provide indications that sports boarding schools did not pose an increased risk of infection, assuming that the facilities prevent virus transmissions with appropriate preventive strategies and hygiene measures. In future pandemic scenarios larger-scale and multicenter studies are necessary to achieve more comprehensive epidemiological data in this field.

Systematic review of seroprevalence of SARS-CoV-2 antibodies and appraisal of evidence, prior to the widespread introduction of vaccine programmes in the WHO European Region, January-December 2020

OBJECTIVES

Systematic review of SARS-CoV-2 seroprevalence studies undertaken in the WHO European Region to measure pre-existing and cumulative seropositivity prior to the roll out of vaccination programmes.

DESIGN

A systematic review of the literature.

DATA SOURCES

We searched MEDLINE, EMBASE and the preprint servers MedRxiv and BioRxiv in the WHO 'COVID-19 Global literature on coronavirus disease' database using a predefined search strategy. Articles were supplemented with unpublished WHO-supported Unity-aligned seroprevalence studies and other studies reported directly to WHO Regional Office for Europe and European Centre for Disease Prevention and Control.

ELIGIBILITY CRITERIA

Studies published before the widespread implementation of COVID-19 vaccination programmes in January 2021 among the general population and blood donors, at national and regional levels.

DATA EXTRACTION AND SYNTHESIS

At least two independent researchers extracted the eligible studies; a third researcher resolved any disagreements. Study risk of bias was assessed using a quality scoring system based on sample size, sampling and testing methodologies.

RESULTS

In total, 111 studies from 26 countries published or conducted between 1 January 2020 and 31 December 2020 across the WHO European Region were included. A significant heterogeneity in implementation was noted across the studies, with a paucity of studies from the east of the Region. Sixty-four (58%) studies were assessed to be of medium to high risk of bias. Overall, SARS-CoV-2 seropositivity prior to widespread community circulation was very low. National seroprevalence estimates after circulation started ranged from 0% to 51.3% (median 2.2% (IQR 0.7-5.2%); n=124), while subnational estimates ranged from 0% to 52% (median 5.8% (IQR 2.3%-12%); n=101), with the highest estimates in areas following widespread local transmission.

CONCLUSIONS

The low levels of SARS-CoV-2 antibody in most populations prior to the start of vaccine programmes underlines the critical importance of targeted vaccination of priority groups at risk of severe disease, while maintaining reduced levels of transmission to minimise population morbidity and mortality.

Molnupiravir for intra-household prevention of COVID-19: The MOVe-AHEAD randomized, placebo-controlled trial

OBJECTIVES

To evaluate the efficacy and safety of molnupiravir for intra-household post-exposure prophylaxis (PEP) of COVID-19.

METHODS

MOVe-AHEAD was a randomized, controlled, double-blind, phase 3 trial comparing molnupiravir (800 mg twice daily for 5 days) with placebo. Eligible participants were adult, unvaccinated, asymptomatic household contacts of patients with laboratory-confirmed COVID-19. The primary efficacy endpoint was the incidence of COVID-19 through day 14 in modified intention-to-treat (MITT) participants (those who received ≥1 dose of study intervention) without detectable SARS-CoV-2 at baseline, termed the MITT-VN population. Superiority of molnupiravir was prespecified as a stratified one-sided p-value of <0.0249 for the treatment difference in this endpoint.

RESULTS

The MITT population comprised 763 participants randomized to molnupiravir and 764 to placebo; 83.6% had anti-SARS-CoV-2 antibodies at baseline. In the MITT-VN population, COVID-19 rates through day 14 were 6.5% with molnupiravir and 8.5% with placebo (one-sided p-value: 0.0848). In the molnupiravir arm, 25/35 of confirmed COVID-19 events (71.4%) occurred after completion of treatment (versus 17/49 [34.7%] for placebo). Adverse event rates were low and similar between molnupiravir and placebo.

CONCLUSIONS

Molnupiravir was well-tolerated but did not meet the prespecified superiority criterion, possibly influenced in part by the high pre-existing immunity in the trial population.

J. S, Meena S, Kumar R, Kaur R, Bairwa M, Kant S, Misra P, Rai SK, Ahmad M, Rahman A. Household transmission investigation for Corona Virus Disease 2019 (COVID-19) in a rural and urban population of north India

BACKGROUND

Transmissibility within closed settings, such as households, can provide a strategic way to characterize the virus transmission patterns because the denominator can be well defined. We aimed to characterize the household transmission of Severe Acute Respiratory Syndrome Coronavirus (SARS CoV-2) and its associated risk factors.

METHODS

This prospective case-ascertained study was conducted among the household contacts of laboratory-confirmed SARS CoV-2 cases residing in Ballabgarh, Haryana. We enrolled 148 index cases and their 645 household contacts between December 16, 2020 and June 24, 2021. We defined household contact as any person who had resided in the same household as a confirmed COVID-19 case. Baseline data collection and sample collection for real time- reverse transcriptase polymerase chain reaction (RT-PCR) and IgM/IgG against SARS CoV-2 were done on day 1 visit, and followed for a period of 28 days. RT-PCR was repeated on day 14 or whenever the contact is symptomatic and blood sample for serology was repeated on day 28. We estimated household secondary infection rate (SIR) and other epidemiological indicators-median incubation period and serial interval. We employed binomial logistic regression to quantify risk factors associated with infection.

RESULTS

The household SIR was 30.5% (95% CI: 27.1-34.1%). The secondary clinical attack rate was 9.3% (95% CI: 7.2-11.8). The risk factors that showed higher susceptibility to infection were household contacts who were the primary care giver of the case, whose index cases were symptomatic, those with underlying medical conditions, those living in overcrowded households, who were sharing toilet with the index cases and also who were not wearing a mask when coming in contact with the case. The median (IQR) incubation period was 4 days (4, 5), mean (SD) serial interval 6.4 (±2.2) days, and median (IQR) serial interval 5 days (5, 7).

CONCLUSION

Households favour secondary transmission of SARS CoV- 2, hence, index cases are recommended to self-isolate and wear masks; and household contacts to follow strict COVID infection control measures within households when a family member is infected.

A network meta-analysis of risk factors of infection among close contacts of COVID-19

Objective

We aimed to use network meta-analysis to compare the impact of infection risk factors of close contacts with COVID-19, identify the most influential factors and rank their subgroups. It can provide a theoretical basis for the rapid and accurate tracking and management of close contacts.

Methods

We searched nine databases from December 1, 2019 to August 2, 2023, which only took Chinese and English studies into consideration. Odd ratios (ORs) were calculated from traditional meta-estimated secondary attack rates (SARs) for different risk factors, and risk ranking of these risk factors was calculated by the surface under the cumulative ranking curve (SUCRA).

Results

25 studies with 152647 participants identified. Among all risk factors, the SUCRA of type of contact was 69.6 % and ranked first. Among six types of contact, compared with transportation contact, medical contact, social contact and other, daily contact increased risk of infection by 12.11 (OR: 12.11, 95 % confidence interval (CI): 6.51-22.55), 7.76 (OR: 7.76, 95 % CI: 4.09-14.73), 4.65 (OR: 4.65, 95 % CI: 2.66-8.51) and 8.23 OR: 8.23, 95 % CI: 4.23-16.01) times, respectively. Overall, SUCRA ranks from highest to lowest as daily contact (94.7 %), contact with pollution subjects (78.4 %), social contact (60.8 %), medical contact (31.8 %), other (27.9 %), transportation contact (6.4 %).

Conclusion

The type of contact had the greatest impact on COVID-19 close contacts infection among the risk factors we included. Daily contact carried the greatest risk of infection among six types of contact, followed by contact with pollution subjects, social contact, other, medical contact and transportation contact. The results can provide scientific basis for rapid assess the risk of infection among close contacts based on fewer risk factors and pay attention to high-risk close contacts during management, thereby reducing tracking and management costs.

Effect of SARS-CoV-2 prior infection and mRNA vaccination on contagiousness and susceptibility to infection

The immunity conferred by SARS-CoV-2 vaccines and infections reduces the transmission of the virus. To answer how the effect of immunity is shared between a reduction of infectiousness and an increased protection against infection, we examined >50,000 positive cases and >110,000 contacts from Geneva, Switzerland (June 2020 to March 2022). We assessed the association between secondary attack rate (i.e. proportion of new cases among contacts) and immunity from natural infection and/or vaccination, stratifying per four SARS-CoV-2 variants and adjusting for index cases and contacts' socio-demographic characteristics and the propensity of the contacts to be tested. Here we show that immunity protected contacts from infection, rather than reducing infectiousness of index cases. Natural infection conferred the strongest immunity. Hybrid immunity did not surpass recent infection. Although of smaller amplitude, the reduction in infectiousness due to vaccination was less affected by time and by the emergence of new SARS-CoV-2 variants than the susceptibility to infection. These findings support the role of vaccine in reducing infectiousness and underscore the complementary role of interventions reducing SARS-CoV-2 propagation, such as mask use or indoor ventilation.

Risk of SARS-CoV-2 transmission in the close contacts in a small rural area in the Veneto Region (NE-Italy): past evidence for future scenarios

Background

During the first pandemic phase of COVID-19, an epidemiological study, named First survey, was conducted on the population of a small rural area in northern Italy. In spring 2020, the results showed how a prolonged lockdown slowed down the spread of the virus.

Methods

After contacting positive First Survey subjects and their families, those who decided to join voluntarily underwent a blood test to assess the presence of qualitative lgG about 2 months after the previous one. This was to determine if IgG persisted in individuals who tested positive in the First Survey as well as to assess the antibody status of their close family members, to determine if they were unintentionally infected.

Results

Based on serological analysis, 35.1% of the samples contained blood IgG. In subjects who tested positive during the First Survey, 62.5% remained IgG positive more than 2 months later. Among family members who were exposed to a positive relative, 23.7% were infected. Linear regression analysis showed that the presence of an infected person within a household resulted in the infection spreading to the others, but not excessively. Induced isolation extinguished the infection regardless of the extent of the contagion (intra-family or extra-family). Micro-outbreaks of SARS-Cov-2 infection which arose in the same household from extra-familial infections played a decisive role on the statistical significance of IgG-positive subjects (p < 0.001).

Discussion

The study reveal 52.6% of the IgG-positive subjects in the Second Survey came from the First Survey and 47.4% were family members previously in contact with positive subjects. Data suggest that there have been undiagnosed patients feeding the spread of the virus since the beginning of the pandemic. In conclusion, for future pandemics, it will be necessary: i) to ensure the rapid isolation of symptomatic patients and the early identification of their close contacts, ii) to carry out the maximum number of tests in the shortest possible time, both on symptomatic and asymptomatic subjects, and iii) to implement information campaigns to make people aware of their risks, and implement clear, non-conflicting communication.

Assessment of the Implementation of a Chatbot-Based Screening for Burnout and COVID-19 Symptoms Among Residents During the Pandemic

Background

Early identification of COVID-19 symptoms and burnout among residents is essential for proper management. Digital assistants might help in the large-scale screening of residents.

Objective

To assess the implementation of a chatbot for tele-screening emotional exhaustion and COVID-19 among residents at a hospital in Brazil.

Methods

From August to October 2020, a chatbot sent participants' phones a daily question about COVID-19 symptoms and a weekly question about emotional exhaustion. After 8 weeks, the residents answered the Maslach Burnout Inventory-Human Services Survey (MBI-HSS). The primary outcome was the reliability of the chatbot in identifying suspect cases of COVID-19 and burnout.

Results

Among the 489 eligible residents, 174 (35.6%) agreed to participate. The chatbot identified 61 positive responses for COVID-19 symptoms, and clinical suspicion was confirmed in 9 residents. User error in the first weeks was the leading cause (57.7%, 30 of 52) of nonconfirmed suspicion. The chatbot failed to identify 3 participants with COVID-19 due to nonresponse. Twelve of 118 (10.2%) participants who answered the MBI-HSS were characterized as having burnout by the MBI-HHS. Two of them were identified as at risk by the chatbot and 8 never answered the emotional exhaustion screening question. Conversely, among the 19 participants identified as at risk for emotional exhaustion by the chatbot, 2 (10.5%) were classified with burnout, and 5 (26.3%) as overextended based on MBI-HHS scores.

Conclusions

The chatbot was able to identify residents suspected of having COVID-19 and those at risk for burnout. Nonresponse was the leading cause of failure in identifying those at risk.

Household transmission dynamics of COVID-19 among residents of Delhi, India: a prospective case-ascertained study

Objective

The aim of this study was to observe the secondary infection rate and transmission dynamics of COVID-19 among household contacts, and their associations with various factors across four dimensions of interaction.

Methods

This was a case-ascertained study among unvaccinated household contacts of a laboratory-confirmed COVID-19 case in New Delhi between December 2020 and July 2021. For this study, 99 index cases and their 316 household contacts were interviewed and sampled (blood and oro-nasal swab) on days 1, 7, 14, and 28.

Results

The secondary infection rate among unvaccinated household contacts was 44.6% (95% confidence interval (CI) 39.1-50.1). The predictors of secondary infection among individual contact levels were: being female (odds ratio (OR) 2.13), increasing age (OR 1.01), symptoms at baseline (OR 3.39), and symptoms during follow-up (OR 3.18). Among index cases, age of the primary case (OR 1.03) and symptoms during follow-up (OR 6.29) were significantly associated with secondary infection. Among household-level and contact patterns, having more rooms (OR 4.44) and taking care of the index case (OR 2.02) were significantly associated with secondary infection.

Conclusion

A high secondary infection rate highlights the need to adopt strict measures and advocate COVID-19-appropriate behaviors. A targeted approach for higher-risk household contacts would efficiently limit infections among susceptible contacts.

Efficiency analysis of rapid antigen test based SARS-CoV-2 in hospital contact tracing and screening regime: test characteristics and cost effectiveness

In the context of the current SARS-CoV-2 pandemic, reliable and cost-efficient screening and testing strategies are crucial to prevent disease transmission and reduce socioeconomic losses. To assess the efficiency of a rapid antigen test (RAT)-based SARS-CoV-2 contact-tracing and screening regime, we conducted a retrospective analysis of RAT and polymerase chain reaction (PCR) test data over a 1-year period, assessed test characteristics and estimated cost-effectiveness. The RAT had a sensitivity of 70.2% overall and 89.3% for people with a high risk of infectivity. We estimated inpatient treatment and quarantined healthcare worker costs of over € 5860.83, whereas the cost of identifying one SARS-CoV-2 positive person by RAT for our patient cohort was € 1210.75. In contrast, the estimated respective PCR cost was € 5043.32. Therefore, a RAT-based contract tracing and screening regime may be an efficient and cost-effective way to contribute to the early identification and prevention of SARS-CoV-2 transmission.

Spatial risk for a superspreading environment: Insights from six urban facilities in six global cities across four continents

Introduction

This study sets out to provide scientific evidence on the spatial risk for the formation of a superspreading environment.

Methods

Focusing on six common types of urban facilities (bars, cinemas, gyms and fitness centers, places of worship, public libraries and shopping malls), it first tests whether visitors' mobility characteristics differ systematically for different types of facility and at different locations. The study collects detailed human mobility and other locational data in Chicago, Hong Kong, London, São Paulo, Seoul and Zurich. Then, considering facility agglomeration, visitors' profile and the density of the population, facilities are classified into four potential spatial risk (PSR) classes. Finally, a kernel density function is employed to derive the risk surface in each city based on the spatial risk class and nature of activities.

Results

Results of the human mobility analysis reflect the geographical and cultural context of various facilities, transport characteristics and people's lifestyle across cities. Consistent across the six global cities, geographical agglomeration is a risk factor for bars. For other urban facilities, the lack of agglomeration is a risk factor. Based on the spatial risk maps, some high-risk areas of superspreading are identified and discussed in each city.

Discussion

Integrating activity-travel patterns in risk models can help identify areas that attract highly mobile visitors and are conducive to superspreading. Based on the findings, this study proposes a place-based strategy of non-pharmaceutical interventions that balance the control of the pandemic and the daily life of the urban population.

Estimating the risk reduction of isolation on COVID-19 nonhousehold transmission and severe/critical illness in nonimmune individuals: September to November 2021

There is growing scientific interest in immunity mandates/passports (IMP) for viral diseases in light of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. IMP isolate those who remain nonimmune from various settings to reduce nonhousehold transmissions from the nonimmune and reduce severe/critical illness among the nonimmune. A major limitation in the scientific literature is that there are currently no methods to quantify how many nonimmune individuals need to be isolated to achieve these purported benefits. This paper develops a procedure for estimating the benefits of IMP using a novel variant of the number needed to treat which we call the number needed to isolate (NNI). We use data from the SARS-CoV-2 pandemic to demonstrate the properties and utility of the NNI and to inform the debate about IMP. We focus on data from the European Union, United Kingdom, United States, Canada, Australia, and Israel during the fall 2021 when the Delta (B.1.617.2) variant predominated.

Household secondary attack rate in mild COVID-19

Background

The coronavirus disease 2019 (COVID-19) pandemic has reached a staggering number of almost 280 million cases worldwide, with over 5.4 million deaths as of 29 December 2021. A further understanding of the factors related to the household spread of the infection might help to bring about specific protocols to curb such transmission.

Objective

This study aims to find the secondary attack rate (SAR) and factors affecting SAR among the households of mild COVID-19 cases.

Methods

An observational study was designed where data of patients admitted at All India Institute of Medical Sciences, New Delhi due to mild COVID-19 were collected, and outcome was noted after the discharge of the patient. Index cases who were the first in the household to have a positive infection only were included. Based on these data, the overall household SAR, factors related to the index case and contacts that affected transmissibility were noted.

Results

A total of 60 index cases having contacts with 184 household members were included in the present study. The household SAR was measured to be 41.85%. At least one positive case was present in 51.67% households. Children below 18 years old had lower odds of getting a secondary infection compared to adults and elderly [odds ratio (OR) = 0.46, 95%CI = 0.22-0.94, p = 0.0383). An exposure period of more than a week was significantly associated with a higher risk of infection (p = 0.029). The rate of transmissibility drastically declined with effective quarantine measures adopted by the index case (OR = 0.13, 95%CI = 0.06-0.26, p < 0.00001). Symptomatic index cases contributed more to the SAR than asymptomatic primaries (OR = 4.74, 95%CI = 1.03-21.82, P = 0.045). Healthcare worker index cases had lower rates of spread (OR = 0.29, 95%CI = 0.15-0.58, P = 0.0003).

Conclusion

The high SAR shows the household is a potential high-risk unit for transmissibility of COVID-19. Proper quarantine measures of all those exposed to the index case can mitigate such spread and lead to reduction of risk of COVID-19 within a household.

Transmission risk of asymptomatic SARS-CoV-2 infection: a systematic review and meta-analysis

Background

Global evidence on the transmission of asymptomatic SARS-CoV-2 infection needs to be synthesized.

Methods

A search of 4 electronic databases (PubMed, EMBASE, Cochrane Library, and Web of Science databases) as of January 24, 2021 was performed. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. Studies which reported the transmission rate among close contacts with asymptomatic SARS-CoV-2 cases were included, and transmission activities occurred were considered. The transmission rates were pooled by zero-inflated beta distribution. The risk ratios (RRs) were calculated using random-effects models.

Results

Of 4923 records retrieved and reviewed, 15 studies including 3917 close contacts with asymptomatic indexes were eligible. The pooled transmission rates were 1.79 per 100 person-days (or 1.79%, 95% confidence interval [CI] 0.41%-3.16%) by asymptomatic index, which is significantly lower than by presymptomatic (5.02%, 95% CI 2.37%-7.66%; p<0.001), and by symptomatic (5.27%, 95% CI 2.40%-8.15%; p<0.001). Subgroup analyses showed that the household transmission rate of asymptomatic index was (4.22%, 95% CI 0.91%-7.52%), four times significantly higher than non-household transmission (1.03%, 95% CI 0.73%-1.33%; p=0.03), and the asymptomatic transmission rate in China (1.82%, 95% CI 0.11%-3.53%) was lower than in other countries (2.22%, 95% CI 0.67%-3.77%; p=0.01).

Conclusions

People with asymptomatic SARS-CoV-2 infection are at risk of transmitting the virus to their close contacts, particularly in household settings. The transmission potential of asymptomatic infection is lower than symptomatic and presymptomatic infections. This meta-analysis provides evidence for predicting the epidemic trend and promulgating vaccination and other control measures. Registered with PROSPERO International Prospective Register of Systematic Reviews, CRD42021269446; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=269446.

Effect of COVID-19 vaccination on the SARS-CoV-2 transmission among social and household close contacts: A cohort study

BACKGROUND

COVID-19 vaccination was expected to reduce SARS-CoV-2 transmission, but the relevance of this effect remains unclear. We aimed to estimate the effectiveness of COVID-19 vaccination of the index cases and their close contacts in reducing the probability of SARS-CoV-2 transmission.

METHODS

Transmission of SARS-CoV-2 infection was evaluated in two cohorts of adult close contacts of COVID-19 confirmed cases (social and household settings) by COVID-19 vaccination status of the index case and the close contact, from April to November 2021 in Navarre, Spain. The effects of vaccination of the index case and the close contact were estimated as (1-adjusted relative risk) × 100%.

RESULTS

Among 19,631 social contacts, 3257 (17%) were confirmed with SARS-CoV-2. COVID-19 vaccination of the index case reduced infectiousness by 44% (95% CI, 27-57%), vaccination of the close contact reduced susceptibility by 69% (95% CI, 65-73%), and vaccination of both reduced transmissibility by 74% (95% CI, 70-78%) in social settings, suggesting some synergy of effects. Among 20,708 household contacts, 6269 (30%) were infected, and vaccine effectiveness estimates were 13% (95% CI, -5% to 28%), 61% (95% CI, 58-64%), and 52% (95% CI, 47-56%), respectively. These estimates were lower in older people and had not relevant differences between the Alpha (April-June) and Delta (July-November) variant periods.

CONCLUSIONS

COVID-19 vaccination reduces infectiousness and susceptibility; however, these effects are insufficient for complete control of SARS-CoV-2 transmission, especially in older people and household setting. Relaxation of preventive behaviors after vaccination may counteract part of the vaccine effect on transmission.

Household Transmission of SARS-CoV-2 and Long-term Immunity in Children: A Prospective Study in Northern Spain

BACKGROUND

The role of children in SARS-CoV-2 transmission and their immune response after infection have been profoundly discussed. Hereby, we analyze both aspects in a Spanish pediatric population.

METHODS

Prospective, multicentre, longitudinal study performed from July 2020 to September 2021 in children up to 14 years old. Venous blood samples were collected every 6 months and serum was analyzed for antibodies against SARS-CoV-2 using a spike (S) and a nucleocapsid (N) protein assays. Household contacts of seropositive children were tested. Household transmission, antibody dynamics, and durability were analyzed.

RESULTS

Two hundred children were recruited and 28 had SARS-CoV-2 antibodies at the end of the study, resulting in an overall seroprevalence of 16.6% (95% CI: 9.5%-19.6%). Most of children (18/28) were secondary cases. The secondary attack rate (SAR) was lower in households with pediatric index cases than in those with adult index cases ( P = 0.023). The median antibody titers in the first positive serology, for the seropositive patients, were 137 BAU/mL (IQR 83.3-427.4) for the S-assay and 132.5 COI (IQR 14.5-170.5) for the N-assay without significant differences between symptomatic and asymptomatic children. The median time between the RT-PCR and the last serology was 7.5 months (IQR 5.2-8.8), and the duration of SARS-CoV-2 antibodies after infection was proven to be at least 18 months. There were no cases of seroreversion.

CONCLUSIONS

(1) Children are not the main drivers of SARS-CoV-2 household transmission. (2) They maintain SARS-CoV-2 antibodies for up to 18 months after infection and the titers are similar between symptomatic and asymptomatic children.

[COVID-19 epidemiology in health and social health workers in the health area of A Coruña and Cee]

OBJECTIVE

Since the beginning of the pandemic, it has become necessary to know the epidemiological evolution of SARS-CoV-2. Therefore, this study aims to describe the characteristics of the casuistry of COVID-19 in health and social-health workers in the health area of A Coruña and Cee during the first epidemic wave, as well as to determine the association between the clinical profile and/or its duration and the condition of RT-PCR repositivization.

MATERIALS AND METHODS

During the study period, 210 cases belonging to healthcare and social-healthcare workers from the healthcare area of A Coruña and Cee were diagnosed. A descriptive analysis of sociodemographic factors was carried out, as well as the search for association between the clinical picture and the duration of detection of a positive RT-PCR.

RESULTS

The most affected categories were nursing (33.3%) and nursing assistants (16.2%). The mean time taken for cases to become RT-PCR negative was 18.3±9.1 days, with a median of 17. It was observed that 26 cases (13.8%) had a positive result in a subsequent RT-PCR, without meeting criteria for reinfection. The existence of skin manifestations and arthralgias was associated with repositivization after adjusting for age and sex (OR=4.6 and OR=6.5, respectively).

CONCLUSIONS

In healthcare professionals diagnosed with COVID-19 during the first wave, symptoms such as dyspnea, skin manifestations and arthralgias led to RT-PCR repositivization after a previous negative result and without meeting criteria for reinfection.

Effect of COVID-19 infection related experiences on social behaviors when a state of emergency is declared: a cohort study

BACKGROUND

Restricting the movement of the public to gathering places and limiting close physical contact are effective measures against COVID-19 infection. In Japan, states of emergency have been declared in specific prefectures to reduce public movement and control COVID-19 transmission. We investigated how COVID-19 infection related experiences including people with a history of infection, people with a history of close contact, and people whose acquaintances have been infected, affected self-restraint from social behaviors during the second state of emergency in Japan.

METHODS

A prospective cohort study was conducted among workers aged 20-65 years using data from an internet survey. The baseline survey was conducted on December 22-25, 2020, and a follow-up survey was on February 18-19, 2021. There were 19,051 participants who completed both surveys and were included in the final analysis. We identified eight social behaviors: (1) eating out (4 people or fewer); (2) eating out (5 people or more); (3) gathering with friends and colleagues; (4) day trip; (5) overnight trip (excluding visiting home); (6) visiting home; (7) shopping for daily necessities; and (8) shopping for other than daily necessities. We set self-restraint regarding each social behavior after the second state of emergency was declared in January 2021 as the dependent variable, and COVID-19 infection related experiences as independent variables. Odds ratios were estimated using multilevel logistic regression analyses nested in the prefecture of residence.

RESULTS

Significant differences by COVID-19 infection related experiences were identified: compared to people without COVID-19 related experiences, people with a history of COVID-19 were less likely self-restraint from most social behaviors. People whose acquaintance had been diagnosed with COVID-19 were significantly more likely to refrain from most social behaviors. There was no significant difference in any social behaviors for people with a history of close contact only.

CONCLUSION

To maximize the effect of a state of emergency, health authorities should disseminate information for each person in the target population, taking into account potential differences related to the infection related experiences.

Risk factors for SARS-CoV-2 transmission in close contacts of adults at high risk of infection due to occupation: results from the contact tracing strategy of the CoVIDA epidemiological surveillance study in Bogotá, Colombia, in 2020-2021

OBJECTIVES

To estimate the risk factors for SARS-CoV-2 transmission in close contacts of adults at high risk of infection due to occupation, participants of the CoVIDA study, in Bogotá D.C., Colombia.

SETTING

The CoVIDA study was the largest COVID-19 intensified sentinel epidemiological surveillance study in Colombia thus far, performing over 60 000 RT-PCR tests for SARS-CoV-2 infection. The study implemented a contact tracing strategy (via telephone call) to support traditional surveillance actions performed by the local health authority.

PARTICIPANTS

Close contacts of participants from the CoVIDA study.

PRIMARY AND SECONDARY OUTCOME MEASURES

SARS-CoV-2 testing results were obtained (RT-PCR with CoVIDA or self-reported results). The secondary attack rate (SAR) was calculated using contacts and primary cases features.

RESULTS

The CoVIDA study performed 1257 contact tracing procedures on primary cases. A total of 5551 close contacts were identified and 1050 secondary cases (21.1%) were found. The highest SAR was found in close contacts: (1) who were spouses (SAR=32.7%; 95% CI 29.1% to 36.4%), (2) of informally employed or unemployed primary cases (SAR=29.1%; 95% CI 25.5% to 32.8%), (3) of symptomatic primary cases (SAR of 25.9%; 95% CI 24.0% to 27.9%) and (4) living in households with more than three people (SAR=22.2%; 95% CI 20.7% to 23.8%). The spouses (OR 3.85; 95% CI 2.60 to 5.70), relatives (OR 1.89; 95% CI 1.33 to 2.70) and close contacts of a symptomatic primary case (OR 1.48; 95% CI 1.24 to 1.77) had an increased risk of being secondary cases compared with non-relatives and close contacts of an asymptomatic index case, respectively.

CONCLUSIONS

Contact tracing strategies must focus on households with socioeconomic vulnerabilities to guarantee isolation and testing to stop the spread of the disease.

Use of surveillance data to elucidate household clustering of SARS-CoV-2 in Fulton County, Georgia a major metropolitan area

BACKGROUND

Households are important for SARS-CoV-2 transmission due to high intensity exposure in enclosed spaces over prolonged durations. We quantified and characterized household clustering of COVID-19 cases in Fulton County, Georgia.

METHODS

We used surveillance data to identify all confirmed COVID-19 cases in Fulton County. Household clustered cases were defined as cases with matching residential address. We described the proportion of COVID-19 cases that were clustered, stratified by age over time and explore trends in age of first diagnosed case within households and subsequent household cases.

RESULTS

Between June 1, 2020 and October 31, 2021, 31,449(37%) of 106,233 cases were clustered in households. Children were the most likely to be in household clusters than any other age group. Initially, children were rarely (∼ 10%) the first cases diagnosed in the household but increased to almost 1 of 3 in later periods.

DISCUSSION

One-third of COVID-19 cases in Fulton County were part of a household cluster. Increasingly children were the first diagnosed case, coinciding with temporal trends in vaccine roll-out among the elderly and the return to in-person schooling in Fall 2021. Limitations include restrictions to cases with a valid address and unit number and that the first diagnosed case may not be the infection source for the household.

Attack Rate for Wild-Type SARS-CoV-2 during Air Travel: Results from 46 Flights Traced by German Health Authorities, January-March and June-August 2020

Background

Evidence on the risk of SARS-CoV-2 transmission during air travel is scarce. We aimed to estimate the attack rate for wild-type SARS-CoV-2 to improve the evidence base for the adaptation of nonpharmaceutical intervention (NPI) strategies aboard airplanes.

Methods

In collaboration with German Public Health Authorities (PHA), we conducted a follow-up of in-flight SARS-CoV-2 contact persons. We included those contact persons whom the Emergency Operations Centre at the Robert Koch-Institute had forwarded to PHA between January to March 2020 (before masking on flights became mandatory) and June to August 2020 (after the introduction of mandatory masking). We retrospectively collected data on whether these contact persons had been successfully contacted, had become symptomatic and had been tested for SARS-CoV-2, and whether alternative exposures other than the flight were known.

Results

Complete data that allowed for the calculation of attack rates were available for 108 contact persons (median age of 36 (IQR 24-53), 40% female), traveling on 46 flights with a median flight duration of 3 hours (IQR 2-3.5). 62 of these persons travelled after masking on flights became mandatory. 13/87 developed symptoms, 44/77 were tested (no data for 21 and 31). 13 persons (9 of whom had been SARS-CoV-2 positive) were excluded from the analysis of attack rates due to a likely alternative exposure. We thus identified 4 probable in-flight transmissions (2 of which occurred after the introduction of mandatory masking). The overall attack rate resulted in 4.2% (4/95; 95% CI: 1.4%-11.0%). Considering flights after mandatory masking, the attack rate was 3.6% (2/56, 95% CI 0.6%-13.4%), before masking 5.1% (2/39, 95% CI 0.9%-18.6%).

Conclusions

The risk of wild-type SARS-CoV-2 transmission during air travel seemed low, but not negligible. In order to formulate an effective, evidence-based NPI protocol for air travel, further studies considering the different transmissibility of SARS-CoV-2 variants of concern and vaccination status are needed.

Neighbourhood-level socio-demographic characteristics and risk of COVID-19 incidence and mortality in Ontario, Canada: A population-based study

OBJECTIVES

We aimed to estimate associations between COVID-19 incidence and mortality with neighbourhood-level immigration, race, housing, and socio-economic characteristics.

METHODS

We conducted a population-based study of 28,808 COVID-19 cases in the provincial reportable infectious disease surveillance systems (Public Health Case and Contact Management System) which includes all known COVID-19 infections and deaths from Ontario, Canada reported between January 23, 2020 and July 28, 2020. Residents of congregate settings, Indigenous communities living on reserves or small neighbourhoods with populations <1,000 were excluded. Comparing neighbourhoods in the 90th to the 10th percentiles of socio-demographic characteristics, we estimated the associations between 18 neighbourhood-level measures of immigration, race, housing and socio-economic characteristics and COVID-19 incidence and mortality using Poisson generalized linear mixed models.

RESULTS

Neighbourhoods with the highest proportion of immigrants (relative risk (RR): 4.0, 95%CI:3.5-4.5) and visible minority residents (RR: 3.3, 95%CI:2.9-3.7) showed the strongest association with COVID-19 incidence in adjusted models. Among individual race groups, COVID-19 incidence was highest among neighbourhoods with the high proportions of Black (RR: 2.4, 95%CI:2.2-2.6), South Asian (RR: 1.9, 95%CI:1.8-2.1), Latin American (RR: 1.8, 95%CI:1.6-2.0) and Middle Eastern (RR: 1.2, 95%CI:1.1-1.3) residents. Neighbourhoods with the highest average household size (RR: 1.9, 95%CI:1.7-2.1), proportion of multigenerational families (RR: 1.8, 95%CI:1.7-2.0) and unsuitably crowded housing (RR: 2.1, 95%CI:2.0-2.3) were associated with COVID-19 incidence. Neighbourhoods with the highest proportion of residents with less than high school education (RR: 1.6, 95%CI:1.4-1.8), low income (RR: 1.4, 95%CI:1.2-1.5) and unaffordable housing (RR: 1.6, 95%CI:1.4-1.8) were associated with COVID-19 incidence. Similar inequities were observed across neighbourhood-level sociodemographic characteristics and COVID-19 mortality.

CONCLUSIONS

Neighbourhood-level inequities in COVID-19 incidence and mortality were observed in Ontario, with excess burden experienced in neighbourhoods with a higher proportion of immigrants, racialized populations, large households and low socio-economic status.

Surgical mask wearing behaviour in COVID-19 pandemic and influenza seasons: a cross-sectional study on healthcare professional students and staff's perspective in Southern California

OBJECTIVE

To investigate healthcare professional staff and students' perception of wearing surgical masks before and after their experience with the COVID-19 pandemic, and to evaluate the impact on mask wearing behaviour in future influenza seasons.

DESIGN

Cross-sectional study using anonymous survey.

SETTING AND PARTICIPANTS

Healthcare students and staff from a healthcare academic institution in Southern California participated in the mask survey study. Survey results were collected from June to November 2021. A total of 305 respondents responded to the survey, with 173 being healthcare students and 132 being working healthcare staff.

OUTCOMES

The study examined respondents' perceptions and hospital mask wearing behaviour before and after their COVID-19 pandemic experience, as well as during previous and future influenza seasons.

RESULTS

Two hundred and sixty-four (86.6%) respondents agreed that wearing a surgical mask reduces infection and limits transmission of infectious disease, yet prior to the pandemic, only a small proportion wore a mask in the hospital or during patient care. After experiencing the COVID-19 pandemic, more respondents indicated that they would continue to wear a mask when they are in a hospital in general (n=145, 47.5%), during patient care (n=262, 85.9%), during influenza seasons throughout the hospital (n=205, 67.2%) and during influenza seasons during patient care (n=270, 88.5%).

CONCLUSION

The pandemic experience has greatly influenced the health prevention behaviours of healthcare students and staff. After the pandemic, many respondents will continue to practice surgical mask wearing behaviour in the hospital, especially during face-to-face patient care. This demonstrates a significant change in health prevention perceptions among the current and the future generation of healthcare professionals.

Household Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 From Adult Index Cases With and Without Human Immunodeficiency Virus in South Africa, 2020-2021: A Case-Ascertained, Prospective, Observational Household Transmission Study

BACKGROUND

In South Africa, 19% of adults are living with human immunodeficiency virus (HIV; LWH). Few data on the influence of HIV on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) household transmission are available.

METHODS

We performed a case-ascertained, prospective household transmission study of symptomatic adult index SARS-CoV-2 cases LWH and not living with HIV (NLWH) and their contacts from October 2020 to September 2021. Households were followed up 3 times a week for 6 weeks to collect nasal swabs for SARS-CoV-2 testing. We estimated household cumulative infection risk (HCIR) and duration of SARS-CoV-2 positivity (at a cycle threshold value <30 as proxy for high viral load).

RESULTS

HCIR was 59% (220 of 373), not differing by index HIV status (60% LWH vs 58% NLWH). HCIR increased with index case age (35-59 years: adjusted OR [aOR], 3.4; 95% CI, 1.5-7.8 and ≥60 years: aOR, 3.1; 95% CI, 1.0-10.1) compared with 18-34 years and with contacts' age, 13-17 years (aOR, 7.1; 95% CI, 1.5-33.9) and 18-34 years (aOR, 4.4; 95% CI, 1.0-18.4) compared with <5 years. Mean positivity was longer in cases LWH (adjusted hazard ratio, 0.4; 95% CI, .1-.9).

CONCLUSIONS

Index HIV status was not associated with higher HCIR, but cases LWH had longer positivity duration. Adults aged >35 years were more likely to transmit and individuals aged 13-34 to be infected SARS-CoV-2 in the household. As HIV infection may increase transmission, health services must maintain HIV testing and antiretroviral therapy initiation.

Symptomatic, Presymptomatic, and Asymptomatic Transmission of SARS-CoV-2 in a University Student Population, August-November 2020

OBJECTIVES

The impact and risk of SARS-CoV-2 transmission from asymptomatic and presymptomatic hosts remains an open question. This study measured the secondary attack rates (SARs) and relative risk (RR) of SARS-CoV-2 transmission from asymptomatic and presymptomatic index cases as compared with symptomatic index cases.

METHODS

We used COVID-19 test results, daily health check reports, and contact tracing data to measure SARs and corresponding RRs among close contacts of index cases in a cohort of 12 960 young adults at the University of Notre Dame in Indiana for 103 days, from August 10 to November 20, 2020. Further analysis included Fisher exact tests to determine the association between symptoms and COVID-19 infection and z tests to determine statistical differences between SARs.

RESULTS

Asymptomatic rates of transmission of SARS-CoV-2 were higher (SAR = 0.19; 95% CI, 0.14-0.24) than was estimated in prior studies, producing an RR of 0.75 (95% CI, 0.54-1.07) when compared with symptomatic transmission. In addition, the transmission rate associated with presymptomatic cases (SAR = 0.25; 95% CI, 0.21-0.30) was approximately the same as that for symptomatic cases (SAR = 0.25; 95% CI, 0.19-0.31). Furthermore, different symptoms were associated with different transmission rates.

CONCLUSIONS

Asymptomatic and presymptomatic hosts of SARS-CoV-2 are a risk for community spread of COVID-19, especially with new variants emerging. Moreover, typical symptom checks may easily miss people who are asymptomatic or presymptomatic but still infectious. Our study results may be used as a guide to analyze the spread of SARS-CoV-2 variants and help inform appropriate public health measures as they relate to asymptomatic and presymptomatic cases.

Transmission of SARS-CoV-2 in standardised first few X cases and household transmission investigations: A systematic review and meta-analysis

We aimed to estimate the household secondary infection attack rate (hSAR) of SARS-CoV-2 in investigations aligned with the WHO Unity Studies Household Transmission Investigations (HHTI) protocol. We conducted a systematic review and meta-analysis according to PRISMA 2020 guidelines. We searched Medline, Embase, Web of Science, Scopus and medRxiv/bioRxiv for "Unity-aligned" First Few X cases (FFX) and HHTIs published 1 December 2019 to 26 July 2021. Standardised early results were shared by WHO Unity Studies collaborators (to 1 October 2021). We used a bespoke tool to assess investigation methodological quality. Values for hSAR and 95% confidence intervals (CIs) were extracted or calculated from crude data. Heterogeneity was assessed by visually inspecting overlap of CIs on forest plots and quantified in meta-analyses. Of 9988 records retrieved, 80 articles (64 from databases; 16 provided by Unity Studies collaborators) were retained in the systematic review; 62 were included in the primary meta-analysis. hSAR point estimates ranged from 2% to 90% (95% prediction interval: 3%-71%; I 2 = 99.7%); I 2 values remained >99% in subgroup analyses, indicating high, unexplained heterogeneity and leading to a decision not to report pooled hSAR estimates. FFX and HHTI remain critical epidemiological tools for early and ongoing characterisation of novel infectious pathogens. The large, unexplained variance in hSAR estimates emphasises the need to further support standardisation in planning, conduct and analysis, and for clear and comprehensive reporting of FFX and HHTIs in time and place, to guide evidence-based pandemic preparedness and response efforts for SARS-CoV-2, influenza and future novel respiratory viruses.

The role of children in household transmission of COVID-19: a systematic review and meta-analysis

OBJECTIVES

To explore household transmissibility of SARS-CoV-2 in children in new-variants dominating periods.

METHODS

Through retrieval in PubMed and Embase, studies were included in two parts: meta-analysis of the household secondary attack rate (SAR) and case analysis of household pediatric infections.

RESULTS

A total of 95 articles were included: 48 for meta-analysis and 47 for case analysis. Pediatric COVID-19 only comprised a minority of the household transmission. The total pooled household SAR of child index cases and contacts were 0.20 (95% confidence interval [CI]: 0.15-0.26) and 0.24 (95% CI: 0.18-0.30). Lower household transmissibility was reported in both child index cases and contacts than in adults (relative risk [RR] = 0.64, 95% CI: 0.50-0.81; RR = 0.74, 95% CI: 0.64-0.85). Younger children were as susceptible as the older children (RR = 0.89, 95% CI: 0.72-1.10). Through subgroup analyses of different variants and periods, increased household SAR was observed in children (Wild: 0.20; Alpha: 0.42; Delta: 0.35; Omicron: 0.56), and no significant difference was found in household SAR between children and adults when new variants dominated.

CONCLUSION

Although children were found not to be dominant in the household transmission, their transmissibility of SARS-CoV-2 appeared to be on the rise as new variants emerged.

Factors Associated With Using the COVID-19 Mobile Contact-Tracing App Among Individuals Diagnosed With SARS-CoV-2 in Amsterdam, the Netherlands: Observational Study

Background

Worldwide, efforts are being made to stop the COVID-19 pandemic caused by SARS-CoV-2. Contact tracing and quarantining are key in limiting SARS-CoV-2 transmission. Mathematical models have shown that the time between infection, isolation of cases, and quarantining of contacts are the most important components that determine whether the pandemic can be controlled. Mobile contact-tracing apps could accelerate the tracing and quarantining of contacts, including anonymous contacts. However, real-world observational data on the uptake and determinants of contact-tracing apps are limited.

Objective

The aim of this paper is to assess the use of a national Dutch contact-tracing app among notified cases diagnosed with SARS-CoV-2 infection and investigate which characteristics are associated with the use of the app.

Methods

Due to privacy regulations, data from the app could not be used. Instead, we used anonymized SARS-CoV-2 routine contact-tracing data collected between October 28, 2020, and February 26, 2021, in the region of Amsterdam, the Netherlands. Complete case logistic regression analysis was performed to identify which factors (age, gender, country of birth, municipality, number of close contacts, and employment in either health care or education) were associated with using the app. Age and number of close contacts were modelled as B-splines due to their nonlinear relationship.

Results

Of 29,766 SARS-CoV-2 positive cases, 4824 (16.2%) reported app use. Median age of cases was 41 (IQR 29-55) years, and 46.7% (n=13,898) were male. In multivariable analysis, males (adjusted odds ratio [AOR] 1.11, 95% CI 1.04-1.18) and residents of municipalities surrounding Amsterdam were more likely to use the app (Aalsmeer AOR 1.34, 95% CI 1.13-1.58; Ouder-Amstel AOR 1.96, 95% CI 1.54-2.50), while people born outside the Netherlands, particularly those born in non-Western countries (AOR 0.33, 95% CI 0.30-0.36), were less likely to use the app. Odds of app use increased with age until the age of 58 years and decreased sharply thereafter (P<.001). Odds of app use increased with number of contacts, peaked at 8 contacts, and then decreased (P<.001). Individuals working in day care, home care, and elderly nursing homes were less likely to use the app.

Conclusions

Contact-tracing app use among people with confirmed SARS-CoV-2 infection was low in the region of Amsterdam. This diminishes the potential impact of the app by hampering the ability to warn contacts. Use was particularly low among older people, people born outside the Netherlands, and people with many contacts. Use of the app was also relatively low compared to those from some other European countries, some of which had additional features beyond contact tracing, making them potentially more appealing. For the Dutch contact-tracing app to have an impact, uptake needs to be higher; therefore, investing more into promotional efforts and additional features could be considered.

SARS-CoV-2 viral load is associated with risk of transmission to household and community contacts

Background

Factors that lead to successful SARS-CoV-2 transmission are still not well described. We investigated the association between a case’s viral load and the risk of transmission to contacts in the context of other exposure-related factors.

Methods

Data were generated through routine testing and contact tracing at a large university. Case viral loads were obtained from cycle threshold values associated with a positive polymerase chain reaction test result from October 1, 2020 to April 15, 2021. Cases were included if they had at least one contact who tested 3–14 days after the exposure. Case-contact pairs were formed by linking index cases with contacts. Chi-square tests were used to evaluate differences in proportions of contacts testing positive. Generalized estimating equation models with a log link were used to evaluate whether viral load and other exposure-related factors were associated with a contact testing positive.

Results

Median viral load among the 212 cases included in the study was 5.6 (1.8–10.4) log₁₀ RNA copies per mL of saliva. Among 365 contacts, 70 (19%) tested positive following their exposure; 36 (51%) were exposed to a case that was asymptomatic or pre-symptomatic on the day of exposure. The proportion of contacts that tested positive increased monotonically with index case viral load (12%, 23% and 25% corresponding to < 5, 5–8 and > 8 log₁₀ copies per mL, respectively; X² = 7.18, df = 2, p = 0.03). Adjusting for cough, time between test and exposure, and physical contact, the risk of transmission to a close contact was significantly associated with viral load (RR = 1.27, 95% CI 1.22–1.32).

Conclusions

Further research is needed to understand whether these relationships persist for newer variants. For those variants whose transmission advantage is mediated through a high viral load, public health measures could be scaled accordingly. Index cases with higher viral loads could be prioritized for contact tracing and recommendations to quarantine contacts could be made according to the likelihood of transmission based on risk factors such as viral load.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07663-1.

Sociodemographic factors and self-restraint from social behaviors during the COVID-19 pandemic in Japan: A cross-sectional study

The control of human flow has led to better control of COVID-19 infections. Japan's state of emergency, unlike other countries, is not legally binding but is rather a request for individual self-restraint; thus, factors must be identified that do not respond to self-restraint, and countermeasures considered for those factors to enhance its efficacy. We examined the relationship between sociodemographic factors and self-restraint toward social behaviors during a pandemic in Japan. This cross-sectional study used data for February 18-19, 2021, obtained from an internet survey; 19,560 participants aged 20-65 were included in the analysis. We identified five relevant behaviors: (1) taking a day trip; (2) eating out with five people or more; (3) gathering with friends and colleagues; (4) shopping for other than daily necessities; (5) shopping for daily necessities. Multilevel logistic regression analyses were used to examine the relationship between sociodemographic factors and self-restraint for each of the behaviors. Results showed that for behaviors other than shopping for daily necessities, women, those aged 60-65, married people, highly educated people, high-income earners, desk workers and those who mainly work with interpersonal communication, and those with underlying disease reported more self-restraint. Older people had less self-restraint than younger people toward shopping for daily necessities; an underlying disease had no effect on the identified behavior. Specialized interventions for these groups that include recommendations for greater self-restraint may improve the efficacy of the implementing measures that request self-restraint.

Impact of Age and Symptom Development on SARS-CoV-2 Transmission in Households With Children-Maryland, New York, and Utah, August 2020-October 2021

Background

Households are common places for spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We investigated factors associated with household transmission and acquisition of SARS-CoV-2.

Methods

Households with children age <18 years were enrolled into prospective, longitudinal cohorts and followed from August 2020 to August 2021 in Utah, September 2020 to August 2021 in New York City, and November 2020 to October 2021 in Maryland. Participants self-collected nasal swabs weekly and with onset of acute illness. Swabs were tested for SARS-CoV-2 using reverse transcription polymerase chain reaction. We assessed factors associated with SARS-CoV-2 acquisition using a multilevel logistic regression adjusted for household size and clustering and SARS-CoV-2 transmission using a logistic regression adjusted for household size.

Results

Among 2053 people (513 households) enrolled, 180 people (8.8%; in 76 households) tested positive for SARS-CoV-2. Compared with children age <12 years, the odds of acquiring infection were lower for adults age ≥18 years (adjusted odds ratio [aOR], 0.34; 95% CI, 0.14-0.87); however, this may reflect vaccination status, which protected against SARS-CoV-2 acquisition (aOR, 0.17; 95% CI, 0.03-0.91). The odds of onward transmission were similar between symptomatic and asymptomatic primary cases (aOR, 1.00; 95% CI, 0.35-2.93) and did not differ by age (12-17 years vs <12 years: aOR, 1.08; 95% CI, 0.20-5.62; ≥18 years vs <12 years: aOR, 1.70; 95% CI, 0.52-5.83).

Conclusions

Adults had lower odds of acquiring SARS-CoV-2 compared with children, but this association might be influenced by coronavirus disease 2019 (COVID-19) vaccination, which was primarily available for adults and protective against infection. In contrast, all ages, regardless of symptoms and COVID-19 vaccination, had similar odds of transmitting SARS-CoV-2. Our findings underscore the importance of SARS-CoV-2 mitigation measures for persons of all ages.

COVID-19: impact on Public Health and hypothesis-driven investigations on genetic susceptibility and severity

COVID-19 is a new complex multisystem disease caused by the novel coronavirus SARS-CoV-2. In slightly over 2 years, it infected nearly 500 million and killed 6 million human beings worldwide, causing an unprecedented coronavirus pandemic. Currently, the international scientific community is engaged in elucidating the molecular mechanisms of the pathophysiology of SARS-CoV-2 infection as a basis of scientific developments for the future control of COVID-19. Global exome and genome analysis efforts work to define the human genetics of protective immunity to SARS-CoV-2 infection. Here, we review the current knowledge regarding the SARS-CoV-2 infection, the implications of COVID-19 to Public Health and discuss genotype to phenotype association approaches that could be exploited through the selection of candidate genes to identify the genetic determinants of severe COVID-19.

Household Transmission of SARS-CoV-2 in Bhutan

Introduction

The transmission trend of SARS-CoV-2 is continuously evolving. Understanding the dynamics in different settings is crucial for any effective containment measures. We aimed to study the characteristics of household transmission of SARS-CoV-2 in Bhutanese households by determining the transmissibility within household contacts of confirmed COVID-19 index cases and their factors of infectivity.

Methods

We conducted a retrospective observational study on household transmission in 306 household contacts of 93 COVID-19 positive index cases diagnosed from April 16, 2021, to June 30, 2021. A pro forma was used to collect data on the epidemiological, demographic, and clinical profile of all recruited individuals. Secondary attack rates (SAR) were calculated, and risk factors for transmission were estimated.

Results

180 of 306 household contacts developed secondary household transmission (SAR 58.8%; 95% CI: 53.2-64.2). The median age of household contacts was 22 years. The median household size was 4 (mean 4.3 ± 2.199) members. Contacts exposed to adult index cases (aPR 1; 95% CI 1, 1.02, p = 0.01) and vaccinated index cases (uPR 0.41, 95% CI 0.25, 0.66, p < 0.001) had a higher SAR and prevalence of secondary infections.

Conclusions

Our findings suggest substantial evidence of secondary infections among household contacts, especially in the context of public health mandated lockdowns. Aggressive early contact tracing and case identification with subsequent case isolation from other household members remains a crucial step in preventing secondary transmission.

Relationship between moral sensitivity and the quality of nursing care for the elderly with Covid-19 in Iranian hospitals

BACKGROUND

The quality of care has a significant impact on the condition of elderly patients. Many factors affect the quality of care, including ethical considerations. Ethical considerations, such as moral sensitivity, change in times of crisis. The present study was conducted to assess the relationship between moral sensitivity and the quality of nursing care for the elderly with Covid-19 in Iranian hospitals.

METHODS

This was a cross-sectional descriptive correlational study. The participants included 445 nurses that were selected by quota sampling method from hospitals admitting COVID-19 patients. The data were collected using the Moral Sensitivity Questionnaire (MSQ) and Quality Patient Care Scale (QUALPAC) as self-reports. We used the SPSS software v.16 for statistical analysis.

RESULTS

The total score of moral sensitivity and quality of care was 52.29 ± 16.44 and 2.83 ± 0.23, respectively. Moral sensitivity negatively correlates with psychological, social, and physical aspects (P < 0.05). Modifying autonomy, interpersonal orientation, and experiencing moral conflict predicted β = 0.10 of the psychosocial aspect of quality of care. Structural moral meaning and expressing benevolence predicted the changes in the physical dimension of quality of care (β = 0.02).

CONCLUSION

The quality of care had a significant inverse correlation with moral sensitivity. Multiple regression analysis showed that modifying autonomy, interpersonal orientation, and experiencing moral conflict could predict the psychosocial dimensions. Structuring moral meaning could predict the physical dimension. The communication aspects were not related to any of the dimensions of moral sensitivity.

COVID-19 disease in children presenting to the pediatric emergency department: A multicenter study with 8886 cases from Turkey

Background

The aim was to evaluate the epidemiological, clinical, laboratory, and radiologic data of children with SARS-CoV-2 positivity by polymerase chain reaction (PCR) together with treatment strategies and clinical outcomes and to evaluate cases of multisystem inflammatory syndrome in children (MIS-C) in this population.

Methods

This was a multicenter retrospective observational cohort study performed in the pediatric emergency departments of 19 tertiary hospitals. From March 11, 2020, to May 31, 2021, children who were diagnosed with confirmed nasopharyngeal/tracheal specimen SARS-CoV-2 PCR positivity or positivity for serum-specific antibodies against SARS-CoV-2 were included. Demographics, presence of chronic illness, symptoms, history of contact with SARS-CoV-2 PCR-positive individuals, laboratory and radiologic investigations, clinical severity, hospital admissions, and prognosis were recorded.

Results

A total of 8886 cases were included. While 8799 (99.0%) cases resulted in a diagnosis of SARS-CoV-2 with PCR positivity, 87 (1.0%) patients were diagnosed with MIS-C. Among SARS-CoV-2 PCR-positive patients, 51.0% were male and 8.5% had chronic illnesses. The median age was 11.6 years (IQR: 5.0–15.4) and 737 (8.4%) patients were aged <1 year. Of the patients, 15.5% were asymptomatic. The most common symptoms were fever (48.5%) and cough (30.7%) for all age groups. There was a decrease in the rate of fever as age increased (p < 0.001); the most common age group for this symptom was <1 year with the rate of 69.6%. There was known contact with a SARS-CoV-2 PCR-positive individual in 67.3% of the cases, with household contacts in 71.3% of those cases. In terms of clinical severity, 83 (0.9%) patients were in the severe-critical group. There was hospital admission in 1269 (14.4%) cases, with 106 (1.2%) of those patients being admitted to the pediatric intensive care unit (PICU). Among patients with MIS-C, 60.9% were male and the median age was 6.4 years (IQR: 3.9–10.4). Twelve (13.7%) patients presented with shock. There was hospital admission in 89.7% of these cases, with 29.9% of the patients with MIS-C being admitted to the PICU.

Conclusion

Most SARS-CoV-2 PCR-positive patients presented with a mild clinical course. Although rare, MIS-C emerges as a serious consequence with frequent PICU admission. Further understanding of the characteristics of COVID-19 disease could provide insights and guide the development of therapeutic strategies for target groups.

Prevalence of SARS-CoV-2 IgG antibodies among dental teams in Germany

OBJECTIVES

During the corona pandemic, dental practices temporarily closed their doors to patients except for emergency treatments. Due to the daily occupational exposure, the risk of SARS-CoV-2 transmission among dentists and their team is presumed to be higher than that in the general population. This study examined this issue among dental teams across Germany.

MATERIALS AND METHODS

In total, 2784 participants provided usable questionnaires and dry blood samples. Dry blood samples were used to detect IgG antibodies against SARS-CoV-2. The questionnaires were analyzed to investigate demographic data and working conditions during the pandemic. Multivariable logistic mixed-effects models were applied.

RESULTS

We observed 146 participants with positive SARS-CoV-2 IgG antibodies (5.2%) and 30 subjects with a borderline finding (1.1%). Seventy-four out of the 146 participants with SARS-CoV-2 IgG antibodies did not report a positive SARS-CoV-2 PCR test (50.7%), while 27 participants without SARS-CoV-2 IgG antibodies reported a positive SARS-CoV-2 PCR test (1.1%). Combining the laboratory and self-reported information, the number of participants with a SARS-CoV-2 infection was 179 (6.5%). Though after adjustment for region, mixed-effects models indicated associations of use of rubber dams (OR 1.65; 95% CI: 1.01-2.72) and the number of protective measures (OR 1.16; 95% CI: 1.01-1.34) with increased risk for positive SARS-CoV-2 status, none of those variables was significantly associated with a SARS-CoV-2 status in fully adjusted models.

CONCLUSIONS

The risk of SARS-CoV-2 transmission was not higher among the dental team compared to the general population.

CLINICAL RELEVANCE

Following hygienic regulations and infection control measures ensures the safety of the dental team and their patients.

School Closure Versus Targeted Control Measures for SARS-CoV-2 Infection

OBJECTIVES

To compare effects of school closures with effects of targeted infection prevention and control (IPC) measures in open schools on SARS-CoV-2 infection rates in students.

METHODS

We conducted interrupted time-series analyses to compare trends in infection rates in grades 1-10 in 7 boroughs in Oslo, Norway, between February 15 and April 18, 2021. All schools at all levels had implemented strict IPC measures. While grades 1-4 attended school throughout the study period, school closures were implemented for grades 5-10 from March 17. We obtained individual level data from nationwide registries.

RESULTS

A total of 616, 452, and 446 students in grades 1-4, 5-7 and 8-10, respectively, were registered with a positive SARS-CoV-2 test during the study period, when the α-variant dominated. A statistically significant reduction in postintervention trends was observed for grades 1-4 (coefficient -1.26; 95% confidence interval (CI), -2.44 to -0.09). We did not observe any statistically significant between-group differences in postintervention trends between grades 1-4 and 5-7 (coefficient 0.66; 95% CI, -1.25 to 2.58) nor between grades 1-4 and 8-10 (coefficient -0.63; 95% CI, -2.30 to 1.04). Findings indicate that keeping schools open with strict IPC measures was equally effective as school closures on reducing student infection rates.

CONCLUSIONS

School closure was not more effective than targeted IPC measures in open schools in reducing student infection rates. Our findings suggest that keeping schools open with appropriate IPC measures should be preferred over school closures, considering the negative consequences closures have on students.

Evaluating the effects of second-dose vaccine-delay policies in European countries: A simulation study based on data from Greece

The results of a simulation-based evaluation of several policies for vaccine rollout are reported, particularly focusing on the effects of delaying the second dose of two-dose vaccines. In the presence of limited vaccine supply, the specific policy choice is a pressing issue for several countries worldwide, and the adopted course of action will affect the extension or easing of non-pharmaceutical interventions in the next months. We employ a suitably generalised, age-structure, stochastic SEIR (Susceptible → Exposed → Infectious → Removed) epidemic model that can accommodate quantitative descriptions of the major effects resulting from distinct vaccination strategies. The different rates of social contacts among distinct age-groups (as well as some other model parameters) are informed by a recent survey conducted in Greece, but the conclusions are much more widely applicable. The results are summarised and evaluated in terms of the total number of deaths and infections as well as life years lost. The optimal strategy is found to be one based on fully vaccinating the elderly/at risk as quickly as possible, while extending the time-interval between the two vaccine doses to 12 weeks for all individuals below 75 years old, in agreement with epidemic theory which suggests targeting a combination of susceptibility and infectivity. This policy, which is similar to the approaches adopted in the UK and in Canada, is found to be effective in reducing deaths and life years lost in the period while vaccination is still being carried out.

Epidemiological, Radiographical, and Laboratorial Characteristics of Chinese Asymptomatic Cases With COVID-19: A Systematic Review and Meta-Analysis

The comprehensive understanding of the characteristics of asymptomatic cases are helpful for the identification and management of patients with asymptomatic COVID-19 infection. Four electronic databases were searched from December 1, 2019 to February 8, 2022 for relevant articles. Data synthesis, subgroup analysis, and sensitivity analysis were performed on the included studies. I² and Q tests were applied to evaluate heterogeneity across studies. The risk of publication bias was assessed and visualized using a funnel plot. A total of 45 studies consisting of 2,655 patients with no symptoms at the screening point were included. Pooled results showed that in China, 65% of initial no-symptoms COVID-19 patients did not present any COVID-19-related symptom during follow-up or by end of disease course (asymptomatic infections). High proportions of initial no-symptoms COVID-19 patients (76%) and patients with asymptomatic infection (55%) had abnormal CT features at the screening point. High proportion of patients with asymptomatic infection had been detected Ig G⁺ (72%) and/or Ig M⁺ (57%) at the screening point. The chest CT scan and SARS-CoV-2-specific antibody testing could serve as effective supplementary methods to identify asymptomatic cases in the early stage of SARS-CoV-2 infection. However, the chest CT scan and the SARS-CoV-2-specific IgM and IgG testing should not replace reverse transcription–polymerase chain reaction (RT-PCR) for screening in asymptomatic patients. The combination of repeated RT-PCR, chest CT scans, and the SARS-CoV-2-specific IgM and IgG testing should be performed for those highly suspected SARS-CoV-2 infections.