A Meta-analysis on the Role of Children in Severe Acute Respiratory Syndrome Coronavirus 2 in Household Transmission Clusters

SARS-CoV-2 Delta Variant in Jingmen City, Hubei Province, China, 2021: Children Susceptible and Vaccination Breakthrough Infection

Background

The delta variant (B.1.617.2) of SARS-CoV-2 was the dominant viral strain causing COVID-19 in China, 2021. We reported a SARS-CoV-2 delta variant outbreak in Jingmen City, Hubei Province, China.

Methods

The data of epidemiological, clinical, laboratorial, and vaccination of COVID-19 cases were collected through field investigation and analyzed.

Results

During the outbreak from 4 to 20 August 2021, 58 cases of the SARS-CoV-2 delta variant (B.1.617.2) were identified with 15 (25.9%) asymptomatic and 43 (74.1%) symptomatic (mild and moderate) patients. The mean serial interval was 2.6 days (standard deviation: 2.0, 95% CI: 1.9-3.6). The median age of the patients was 39 years (ranging from 1 to 60 years) with the high proportion in children (19.0%). The secondary attack rate was 9.8% higher from parents to their children (<18 years) (46.2%, 95% CI: 14.8-77.5%) than that between spouses (36.4%, 95% CI: 14.5-58.2%), but no significant difference was observed (p > 0.05). Approximately half (27; 46.6%) of cases were vaccine breakthrough infections. In vaccine breakthrough cases (fully vaccinated), viral loads decreased 1.9-3.4-folds (p < 0.05), duration of viral shedding shortened 5 days (p < 0.05), and the risk of becoming symptomatic from asymptomatic decreased 33% (95% CI: 5-53%) (aged ≥12 years) than those in unvaccinated infections.

Conclusions

Children are highly susceptible to the SARS-CoV-2 delta variant in the COVID-19 outbreak in Jingmen City in 2021. Inactivated vaccine derived from wide-type strain can effectively reduce the viral load, duration of viral shedding, and clinical severity in vaccine breakthrough cases. Our study indicates that protective measures that include full vaccination against COVID-19, especially in children, should be strengthened.

Distinct airway epithelial immune responses after infection with SARS-CoV-2 compared to H1N1

Children are less likely than adults to suffer severe symptoms when infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), while influenza A H1N1 severity is comparable across ages except for the very young or elderly. Airway epithelial cells play a vital role in the early defence against viruses via their barrier and immune functions. We investigated viral replication and immune responses in SARS-CoV-2-infected bronchial epithelial cells from healthy paediatric (n = 6; 2.5-5.6 years old) and adult (n = 4; 47-63 years old) subjects and compared cellular responses following infection with SARS-CoV-2 or Influenza A H1N1. While infection with either virus triggered robust transcriptional interferon responses, including induction of type I (IFNB1) and type III (IFNL1) interferons, markedly lower levels of interferons and inflammatory proteins (IL-6, IL-8) were released following SARS-CoV-2 compared to H1N1 infection. Only H1N1 infection caused disruption of the epithelial layer. Interestingly, H1N1 infection resulted in sustained upregulation of SARS-CoV-2 entry factors FURIN and NRP1. We did not find any differences in the epithelial response to SARS-CoV-2 infection between paediatric and adult cells. Overall, SARS-CoV-2 had diminished potential to replicate, affect morphology and evoke immune responses in bronchial epithelial cells compared to H1N1.

Risk factors associated with household transmission of SARS-CoV-2 in Negeri Sembilan, Malaysia

AIM

Households are a significant venue for the transmission of SARS-CoV-2. We conducted a study to characterise the transmission dynamics and identify risk factors for household transmission of SARS-CoV-2 in Negeri Sembilan, Malaysia.

METHODS

This retrospective observational study included 185 families of paediatric COVID-19 cases from 1 February 2020 to 31 December 2020. We identified the index case for each household and gathered the socio-demographic, epidemiological investigation results and risk factors for household transmission from medical case records. The secondary attack rate was calculated, and logistic regression analyses were used to identify risk factors associated with secondary household transmission of SARS-CoV-2.

RESULTS

Of the 848 household contacts, 466 acquired secondary infections, resulting in a secondary attack rate of 55%. The median age of the secondary cases was 12 years. Female household contacts and household contacts who slept in the same room with the index case were significantly associated with increased risk for COVID-19. Other independent risk factors associated with higher transmission risk in the household included an index case who was symptomatic, a household index case aged greater than 18 years and a male household index case.

CONCLUSIONS

High rates of household transmission of COVID-19 were found, indicating households were a major setting of transmission of SARS-CoV-2. Our data provide insight into the risk factors for household transmission of SARS-CoV-2 in Malaysia.

Transmission dynamics of COVID-19 in household and community settings in the United Kingdom, January to March 2020

BackgroundHouseholds appear to be the highest risk setting for COVID-19 transmission. Large household transmission studies in the early stages of the pandemic in Asia reported secondary attack rates ranging from 5 to 30%.AimWe aimed to investigate the transmission dynamics of COVID-19 in household and community settings in the UK.MethodsA prospective case-ascertained study design based on the World Health Organization FFX protocol was undertaken in the UK following the detection of the first case in late January 2020. Household contacts of cases were followed using enhanced surveillance forms to establish whether they developed symptoms of COVID-19, became confirmed cases and their outcomes. We estimated household secondary attack rates (SAR), serial intervals and individual and household basic reproduction numbers. The incubation period was estimated using known point source exposures that resulted in secondary cases.ResultsWe included 233 households with two or more people with 472 contacts. The overall household SAR was 37% (95% CI: 31-43%) with a mean serial interval of 4.67 days, an R₀ of 1.85 and a household reproduction number of 2.33. SAR were lower in larger households and highest when the primary case was younger than 18 years. We estimated a mean incubation period of around 4.5 days.ConclusionsRates of COVID-19 household transmission were high in the UK for ages above and under 18 years, emphasising the need for preventative measures in this setting. This study highlights the importance of the FFX protocol in providing early insights on transmission dynamics.

Transmission dynamics of COVID-19 in household and community settings in the United Kingdom, January to March 2020

BackgroundHouseholds appear to be the highest risk setting for COVID-19 transmission. Large household transmission studies in the early stages of the pandemic in Asia reported secondary attack rates ranging from 5 to 30%.AimWe aimed to investigate the transmission dynamics of COVID-19 in household and community settings in the UK.MethodsA prospective case-ascertained study design based on the World Health Organization FFX protocol was undertaken in the UK following the detection of the first case in late January 2020. Household contacts of cases were followed using enhanced surveillance forms to establish whether they developed symptoms of COVID-19, became confirmed cases and their outcomes. We estimated household secondary attack rates (SAR), serial intervals and individual and household basic reproduction numbers. The incubation period was estimated using known point source exposures that resulted in secondary cases.ResultsWe included 233 households with two or more people with 472 contacts. The overall household SAR was 37% (95% CI: 31-43%) with a mean serial interval of 4.67 days, an R0 of 1.85 and a household reproduction number of 2.33. SAR were lower in larger households and highest when the primary case was younger than 18 years. We estimated a mean incubation period of around 4.5 days.ConclusionsRates of COVID-19 household transmission were high in the UK for ages above and under 18 years, emphasising the need for preventative measures in this setting. This study highlights the importance of the FFX protocol in providing early insights on transmission dynamics.

The Association between Contact with Children and the Clinical Course of COVID-19

We examined the association between contact with children and the clinical course of COVID-19 among COVID-19-positive adult patients. Participants completed a survey to assess demographics, medical information related to their COVID-19 diagnosis, contact with children at home and at the workplace. Patients were aged 45.68 ± 14.38 years, mostly female (72.1%), 842 were not hospitalized and 167 were hospitalized. At home, there were no differences between groups for the number of child contact hours or total child hours (hours × number of children) per week (P s > 0.05). The number of children at home was greater among patients not hospitalized (P < 0.05), however this was no longer significant after controlling for covariates (P > 0.05). At the workplace, there were no differences between groups (all P s > 0.05). Sub-group analysis found the proportion of patients that were treated in the intensive care unit (ICU) was greater among patients with no child contact (P < 0.05). A secondary analysis found that patients with no child contact had an increased likelihood of thromboembolism (P < 0.05) and a trend towards more overall COVID-19-related complications (P = 0.076). Overall, an association between contact with children and hospitalization was not found when adjusting for covariates. Sub-group analysis indicated a possible protective effect for more severe disease; however, these findings need further study.

Clinical manifestations of COVID-19 differ by age and obesity status

BACKGROUND

Age and obesity status are associated with severe outcomes among hospitalized individuals with COVID-19. It remains unclear whether age and obesity are risk factors for milder COVID-19 illness.

METHODS

We prospectively enrolled SARS-CoV-2-exposed individuals. Participants recorded symptoms for 28 days and were tested for SARS-CoV-2 by reverse transcription polymerase chain reaction (RT-PCR) and serology. Type, number, and duration of symptoms and SARS-CoV-2 laboratory parameters were compared by age and obesity status.

RESULTS

Of 552 individuals enrolled from June 2020 to January 2021, 470 (85.1%) tested positive for SARS-CoV-2 including 261 (55.5%) adults ≥18 years, 61 (13.0%) adolescents 12-17 years, and 148 (31.5%) children <12 years. Children had fewer symptoms (median 2 vs. 3, p < 0.001) lasting fewer days (median 5 vs. 7, p < 0.001) compared with adolescents/adults. Body mass index of 300 (63.8%) individuals classified with overweight or obesity (OWOB). Individuals with OWOB suffered more symptoms compared with individuals without OWOB (median 3 vs. 2, p = 0.037), including more cough and shortness of breath (p = 0.023 and 0.026, respectively). Adolescents with OWOB were more likely to be symptomatic (66.7% vs. 34.2%, p = 0.008) and have longer respiratory symptoms (median 7 vs. 4 days, p = 0.049) compared with adolescents without OWOB. Lower RT-PCR Ct values were found in children and symptomatic individuals compared with adolescent and adults and asymptomatic individuals, respectively (p = 0.001 and 0.022).

CONCLUSIONS

Adolescents and adults with OWOB experience more respiratory symptoms from COVID-19 despite similar viral loads. These findings underscore the importance of vaccinating individuals with OWOB.

Children and Adolescents' Behavioral Patterns in Response to Escalating COVID-19 Restriction Reveal Sex and Age Differences

PURPOSE

The COVID-19 pandemic affects students in a myriad of different ways. Our prospective, longitudinal study in a cohort of students in Hannover, Germany explores behavioral patterns during escalating COVID-19 restrictions.

METHODS

In total, 777 students between the age of 9 and 20 were assessed for their activity engagement, travel patterns, and self-assessed compliance with protective recommendations at six time points between June 2020 and June 2021 (3,564 observations) and were monitored for severe acute respiratory syndrome coronavirus 2 infection by nasal swab polymerase chain reaction and serum antibody titers.

RESULTS

Activity engagement decreased, but self-assessed compliance with measures such as mask wearing and social distancing was stable during escalating restrictions. Although we found no sex difference during the summer break, when incidence was lowest, females engaged in a higher variety of activities than males for all other time points. Older students engaged in more activities and self-assigned themselves lower compliance values than younger ones. Greater involvement in different activities was seen in households which traveled more frequently. Infection rate in our cohort was low (0.03% acute infections, 1.94% positive seroprevalence).

DISCUSSION

Our study supports the view that, overall, students show high compliance with COVID-19 recommendations and restrictions. The identification of subsets, such as female and older students, with higher risk behavioral patterns should be considered when implementing public information campaigns. In light of the low infection rate in our cohort, we conclude that in-person learning can occur safely if extensive protective measures are in place and the incidence in the general population remains moderate.

Non-pharmaceutical intervention levels to reduce the COVID-19 attack ratio among children

The attack ratio in a subpopulation is defined as the total number of infections over the total number of individuals in this subpopulation. Using a methodology based on an age-stratified transmission dynamics model, we estimated the attack ratio of COVID-19 among children (individuals 0-11 years) when a large proportion of individuals eligible for vaccination (age 12 and above) are vaccinated to contain the epidemic among this subpopulation, or the effective herd immunity (with additional physical distancing measures). We describe the relationship between the attack ratio among children, the time to remove infected individuals from the transmission chain and the children-to-children daily contact rate while considering the increased transmissibility of virus variants (using the Delta variant as an example). We illustrate the generality and applicability of the methodology established by performing an analysis of the attack ratio of COVID-19 among children in the population of Canada and in its province of Ontario. The clinical attack ratio, defined as the number of symptomatic infections over the total population, can be informed from the attack ratio and both can be reduced substantially via a combination of reduced social mixing and rapid testing and isolation of the children.

The role of schools in driving SARS-CoV-2 transmission: Not just an open-and-shut case

Keeping schools open without permitting COVID-19 spread has been complicated by conflicting messages around the role of children and schools in fueling the pandemic. Here, we describe methodological limitations of research minimizing SARS-CoV-2 transmission in schools, and we review evidence for safely operating schools while reducing overall SARS-CoV-2 transmission.

COVID-19 and children: medical impact and collateral damage

Children mostly experience mild SARS‐CoV‐2 infections, but the extent of paediatric COVID‐19 disease differs between geographical regions and the distinct pandemic waves. Not all infections in children are mild, some children even show a strong inflammatory reaction resulting in a multisystem inflammatory syndrome. The assessments of paediatric vaccination depend on the efficacy of protection conferred by vaccination, the risk of adverse reactions and whether children contribute to herd immunity against COVID‐19. Children were also the target of consequential public health actions such as school closure which caused substantial harm to children (educational deficits, sociopsychological problems) and working parents. It is, therefore, important to understand the transmission dynamics of SARS‐CoV‐2 infections by children to assess the efficacy of school closures and paediatric vaccination. The societal restrictions to contain the COVID‐19 pandemic had additional negative effects on children’s health, such as missed routine vaccinations, nutritional deprivation and lesser mother–child medical care in developing countries causing increased child mortality as a collateral damage. In this complex epidemiological context, it is important to have an evidence‐based approach to public health approaches. The present review summaries pertinent published data on the role of children in the pandemic, whether they are drivers or followers of the infection chains and whether they are (after elderlies) major sufferers or mere bystanders of the COVID‐19 pandemic.

The present review summaries pertinent published data on the role of children in the pandemic, whether they are drivers or followers of the infection chains and whether they are (after elderlies) major sufferers or mere bystanders of the COVID‐19 pandemic.

Age-dependent pathogenic characteristics of SARS-CoV-2 infection in ferrets

While the seroprevalence of SARS-CoV-2 in healthy people does not differ significantly among age groups, those aged 65 years or older exhibit strikingly higher COVID-19 mortality compared to younger individuals. To further understand differing COVID-19 manifestations in patients of different ages, three age groups of ferrets are infected with SARS-CoV-2. Although SARS-CoV-2 is isolated from all ferrets regardless of age, aged ferrets (≥3 years old) show higher viral loads, longer nasal virus shedding, and more severe lung inflammatory cell infiltration, and clinical symptoms compared to juvenile (≤6 months) and young adult (1–2 years) groups. Furthermore, direct contact ferrets co-housed with the virus-infected aged group shed more virus than direct-contact ferrets co-housed with virus-infected juvenile or young adult ferrets. Transcriptome analysis of aged ferret lungs reveals strong enrichment of gene sets related to type I interferon, activated T cells, and M1 macrophage responses, mimicking the gene expression profile of severe COVID-19 patients. Thus, SARS-CoV-2-infected aged ferrets highly recapitulate COVID-19 patients with severe symptoms and are useful for understanding age-associated infection, transmission, and pathogenesis of SARS-CoV-2.

Here, Kim et al. characterize SARS-CoV-2 infection in juvenile, young, and old aged ferrets to provide a further understanding of differences in COVID-19 severity in humans at different ages. Aged ferrets have higher viral loads, shed virus longer, and mimic the transcriptomic profile of severely infected patients.

The Burden of COVID-19 in Children and Its Prevention by Vaccination: A Joint Statement of the Israeli Pediatric Association and the Israeli Society for Pediatric Infectious Diseases

As of October 2021, SARS-CoV-2 infections were reported among 512,613 children and adolescents in Israel (~33% of all COVID-19 cases). The 5-11-year age group accounted for about 43% (223,850) of affected children and adolescents. In light of the availability of the Pfizer-BioNTech BNT162b2 vaccine against COVID-19 for children aged 5-11 years, we aimed to write a position paper for pediatricians, policymakers and families regarding the clinical aspects of COVID-19 and the vaccination of children against COVID-19. The first objective of this review was to describe the diverse facets of the burden of COVID-19 in children, including the direct effects of hospitalization during the acute phase of the disease, multisystem inflammatory syndrome in children, long COVID and the indirect effects of social isolation and interruption in education. In addition, we aimed to provide an update regarding the efficacy and safety of childhood mRNA COVID-19 vaccination and to instill confidence in pediatricians regarding the benefits of vaccinating children against COVID-19. We reviewed up-to-date Israeli and international epidemiological data and literature regarding COVID-19 morbidity and its sequelae in children, vaccine efficacy in reducing COVID-19-related morbidity and SARS-CoV-2 transmission and vaccine safety data. We conducted a risk-benefit analysis regarding the vaccination of children and adolescents. We concluded that vaccines are safe and effective and are recommended for all children aged 5 to 11 years to protect them from COVID-19 and its complications and to reduce community transmissions. Based on these data, after weighing the benefits of vaccination versus the harm, the Israeli Ministry of Health decided to recommend vaccination for children aged 5-11 years.

SARS-CoV-2 in pediatric cancer: a systematic review

The outbreak of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in December 2019 in Wuhan challenges pediatric oncologists in an unexpected way. We provide a comprehensive overview, which systematically summarizes and grades evidence (QoE) on SARS-CoV-2 infections in pediatric cancer patients at 1.5 years of pandemic. A systematic literature search in PubMed combined with an additional exploratory literature review in other international databases was conducted to identify studies on children (aged < 18 years) with a malignant disease and COVID-19 infections. In total, 45 reports on 1003 pediatric cancer patients with SARS-CoV-2 infections were identified out of 1397 reports analyzed. The clinical course of COVID-19 was reported mild or moderate in 358 patients (41.7%), whereas 11.1% of patients showed severe COVID-19. In 12.7% of patients, chemotherapy was postponed, whereas 19% of patients with different underlying malignancies received chemotherapy during SARS-CoV-2 infection. Twenty-five patients with SARS-CoV-2 infections died, potentially related to COVID-19.

CONCLUSION

Despite a favorable COVID-19 outcome in most pediatric cancer patients, the morbidity is reported higher than in children without comorbidities. However, no severe COVID-19 complications were associated to the continuation of chemotherapy in some cohort studies and reports on two patients. Therefore, the risk of cancer progress or relapse due to interruption of chemotherapy has carefully to be weighed against the risk of severe COVID-19 disease with potentially fatal outcome.

WHAT IS KNOWN

• Most of pediatric patients with malignant diseases show an asymptomatic, mild or moderate clinical course of SARS-CoV-2 infection. • Current need for a basis for decision-making, whether to stop or interrupt cancer treatment in a patient infected with SARS-CoV-2, and when to continue chemotherapy.

WHAT IS NEW

• Review results comprising over 1000 pediatric COVID-19 cancer patients confirm mild courses of SARS-CoV-2 infection in most patients but also show the attributable mortality is at least 10 times higher compared to reports on hospitalized children without comorbidities. • Review identifies that chemotherapy was continued despite SARS-CoV-2 positivity in 18% of patients with individual chemotherapy modification according to the clinical course of SARS-CoV-2 infection and existing comorbidities. On this basis, no severe COVID-19 complications were associated to the continuation of chemotherapy in several cohort studies and two case reports.

Secondary household transmission of SARS-CoV-2 among children and adolescents: Clinical and epidemiological aspects

OBJECTIVE

To evaluate the secondary attack rate (SAR) in children and adolescents, contacts of essential activities workers who were infected by SARS-CoV-2; and to describe associated clinical and epidemiological data.

METHODS

A cross-sectional study conducted in children and adolescents aged 5 to 19 years of age, that were household contacts of parents and other relatives who were infected by SARS-CoV-2 in the city of Goiânia, Central Brazil, from March to October 2020. Sociodemographic and clinical data were collected from all participants. Nasopharyngeal and oropharyngeal swabs were collected and tested for SARS-CoV-2 RNA using real-time reverse transcription polymerase chain reaction (RT-PCR). Factors associated with SARS-CoV-2 infection and SAR were analyzed using Poisson regression.

RESULTS

A total of 267 children and adolescents were investigated. The prevalence of SARS-CoV-2 RNA by the real-time RT-PCR test and/or the presence of COVID-19 associated symptoms (anosmia/ageusia and flu syndrome) was 25.1% (95.0% Confidence Interval [95.0% CI] = 20.3-30.6). More than half (55.1%) of the participants had sygns and symptoms. The most prevalent signs and symptoms in positive individuals were nasal congestion (62.7%), headache (55.2%), cough (50.8%), myalgia (47.8%), runny nose (47.8%), and anosmia (47.8%). The Poisson model showed that the following signs or symptoms were associated with SARS-CoV-2 infection: fever, nasal congestion, decreased appetite, nausea, anosmia, and ageusia. Families that had more than one infected adult, in addition to the index case, presented greater transmissibility to children and adolescents.

CONCLUSIONS

Our results contribute to the hypothesis that children and adolescents are not important sources of transmission of SARS-CoV-2 in the home environment during a period of social distancing and school closure; even though they are susceptible to infection in the household (around ¼ of our study population).

COVID-19 prevention behaviors, trust, and intent to vaccinate among youth at risk for HIV

The current study examines COVID-19 prevention behaviors and vaccine intentions among 83 youth at high risk for HIV. Most youth self-identified as Latinx (52%), cisgender men (84%), and homosexual (66%). Youth self-reported COVID-19 prevention behaviors and intentions to vaccinate. Participants reported wearing face masks, washing hands, and staying six feet apart, but fewer reported leaving home only for essential needs. About one-third reported that they would not get a vaccine, and lack of trust in their doctors and the government were significantly associated with non-intention. To improve efforts towards herd immunity, interventions to improve health messaging from trusted sources for at-risk youth may be necessary to achieve higher vaccine uptake.

SARS-CoV-2 Delta Variant in Jingmen City, Hubei Province, China, 2021: Children Susceptible and Vaccination Breakthrough Infection

BACKGROUND

The delta variant (B.1.617.2) of SARS-CoV-2 was the dominant viral strain causing COVID-19 in China, 2021. We reported a SARS-CoV-2 delta variant outbreak in Jingmen City, Hubei Province, China.

METHODS

The data of epidemiological, clinical, laboratorial, and vaccination of COVID-19 cases were collected through field investigation and analyzed.

RESULTS

During the outbreak from 4 to 20 August 2021, 58 cases of the SARS-CoV-2 delta variant (B.1.617.2) were identified with 15 (25.9%) asymptomatic and 43 (74.1%) symptomatic (mild and moderate) patients. The mean serial interval was 2.6 days (standard deviation: 2.0, 95% CI: 1.9-3.6). The median age of the patients was 39 years (ranging from 1 to 60 years) with the high proportion in children (19.0%). The secondary attack rate was 9.8% higher from parents to their children (<18 years) (46.2%, 95% CI: 14.8-77.5%) than that between spouses (36.4%, 95% CI: 14.5-58.2%), but no significant difference was observed (p > 0.05). Approximately half (27; 46.6%) of cases were vaccine breakthrough infections. In vaccine breakthrough cases (fully vaccinated), viral loads decreased 1.9-3.4-folds (p < 0.05), duration of viral shedding shortened 5 days (p < 0.05), and the risk of becoming symptomatic from asymptomatic decreased 33% (95% CI: 5-53%) (aged ≥12 years) than those in unvaccinated infections.

CONCLUSIONS

Children are highly susceptible to the SARS-CoV-2 delta variant in the COVID-19 outbreak in Jingmen City in 2021. Inactivated vaccine derived from wide-type strain can effectively reduce the viral load, duration of viral shedding, and clinical severity in vaccine breakthrough cases. Our study indicates that protective measures that include full vaccination against COVID-19, especially in children, should be strengthened.

Secondary transmission of SARS-CoV-2 during the first two waves in Japan: Demographic characteristics and overdispersion

Objectives

Super-spreading events caused by overdispersed secondary transmission are crucial in the transmission of COVID-19. However, the exact level of overdispersion, demographics, and other factors associated with secondary transmission remain elusive. In this study, we aimed to elucidate the frequency and patterns of secondary transmission of SARS-CoV-2 in Japan.

Methods

We analyzed 16,471 cases between January 2020 and August 2020. We generated the number of secondary cases distribution and estimated the dispersion parameter (k) by fitting the negative binomial distribution in each phase. The frequencies of the secondary transmission were compared by demographic and clinical characteristics, calculating the odds ratio using logistic regression models.

Results

We observed that 76.7% of the primary cases did not generate secondary cases with an estimated dispersion parameter k of 0.23. The demographic patterns of primary-secondary cases differed between phases, with 20–69 years being the predominant age group. There were higher proportions of secondary transmissions among older individuals, symptomatic patients, and patients with 2 days or more between onset and confirmation.

Conclusions

The study showed the estimation of the frequency of secondary transmission of SARS-CoV-2 and the characteristics of people who generated the secondary transmission.

SARS-CoV-2 infections in households in a peri-urban community of Lima, Peru: A prospective cohort study

Background

We assessed the prevalence and incidence of SARS‐CoV‐2 infections in a prospective study of households in Lima, Peru.

Methods

Households with a child, a young adult 18–50 years, and an adult age >50 years in peri‐urban Lima were followed with twice‐a‐week household visits during a 2‐month period. Nasal swabs and saliva specimens were collected twice weekly, and nasopharyngeal swabs were collected weekly from each participant, regardless of symptoms. Laboratory‐confirmed SARS‐CoV‐2 infection was defined by two RT‐PCR tests from any of the collected specimens within a week. Blood samples collected at enrollment and end of follow‐up were tested with rapid serological tests. We calculated the prevalence and incidence of laboratory‐confirmed SARS‐CoV‐2 infections.

Results

We enrolled 132 participants from 44 households: 44 children, 44 young adults, and 44 older adults. A total of 13 SARS‐CoV‐2 infections were detected in eight households, for an overall period prevalence of 9.85% (95% confidence interval [CI]: 5.35–16.25). Most (61.54%) infections were symptomatic. Eight of 11 (72.73%) SARS‐CoV‐2 detections corresponded to the Lambda variant. During 218.79 person‐months at risk of follow‐up, there were six new SARS‐CoV‐2 infections detected (2.74 per 100 person‐month, 95% CI: 1.25–6.04). At enrollment, 59 of 128 participants tested had positive SARS‐CoV‐2 IgG serology (46.09%, 95% CI: 37.25–55.12). Five of six new infections occurred among participants with negative baseline serology.

Conclusions

We demonstrated high incidence of SARS‐CoV‐2 infections in households, especially among subjects without evidence of prior infection, most of them not detected by the Ministry of Health system.

Parents' Decisions to Vaccinate Children against COVID-19: A Scoping Review

Since 2019, the COVID-19 pandemic has resulted in sickness, hospitalizations, and deaths of the old and young and impacted global social and economy activities. Vaccination is one of the most important and efficient ways to protect against the COVID-19 virus. In a review of the literature on parents’ decisions to vaccinate their children, we found that widespread vaccination was hampered by vaccine hesitancy, especially for children who play an important role in the coronavirus transmission in both family and school. To analyze parent vaccination decision-making for children, our review of the literature on parent attitudes to vaccinating children, identified the objective and subjective influencing factors in their vaccination decision. We found that the median rate of parents vaccinating their children against COVID-19 was 59.3% (IQR 48.60~73.90%). The factors influencing parents’ attitudes towards child vaccination were heterogeneous, reflecting country-specific factors, but also displaying some similar trends across countries, such as the education level of parents. The leading reason in the child vaccination decision was to protect children, family and others; and the fear of side effects and safety was the most important reason in not vaccinating children. Our study informs government and health officials about appropriate vaccination policies and measures to improve the vaccination rate of children and makes specific recommendations on enhancing child vaccinate rates.

SARS-CoV-2 incidence, transmission and reinfection in a rural and an urban setting: results of the PHIRST-C cohort study, South Africa, 2020-2021

BACKGROUND

By August 2021, South Africa experienced three SARS-CoV-2 waves; the second and third associated with emergence of Beta and Delta variants respectively.

METHODS

We conducted a prospective cohort study during July 2020-August 2021 in one rural and one urban community. Mid-turbinate nasal swabs were collected twice-weekly from household members irrespective of symptoms and tested for SARS-CoV-2 using real-time reverse transcription polymerase chain reaction (rRT-PCR). Serum was collected every two months and tested for anti-SARS-CoV-2 antibodies.

RESULTS

Among 115,759 nasal specimens from 1,200 members (follow-up rate 93%), 1976 (2%) were SARS-CoV-2-positive. By rRT-PCR and serology combined, 62% (749/1200) of individuals experienced ≥1 SARS-CoV-2 infection episode, and 12% (87/749) experienced reinfection. Of 662 PCR-confirmed episodes with available data, 15% (n=97) were associated with ≥1 symptom. Among 222 households, 200 (90%) had ≥1 SARS-CoV-2-positive individual. Household cumulative infection risk (HCIR) was 25% (213/856). On multivariable analysis, accounting for age and sex, index case lower cycle threshold value (OR 3.9, 95%CI 1.7-8.8), urban community (OR 2.0,95%CI 1.1-3.9), Beta (OR 4.2, 95%CI 1.7-10.1) and Delta (OR 14.6, 95%CI 5.7-37.5) variant infection were associated with increased HCIR. HCIR was similar for symptomatic (21/110, 19%) and asymptomatic (195/775, 25%) index cases (p=0.165). Attack rates were highest in individuals aged 13-18 years and individuals in this age group were more likely to experience repeat infections and to acquire SARS-CoV-2 infection. People living with HIV who were not virally supressed were more likely to develop symptomatic illness, and shed SARS-CoV-2 for longer compared to HIV-uninfected individuals.

CONCLUSIONS

In this study, 85% of SARS-CoV-2 infections were asymptomatic and index case symptom status did not affect HCIR, suggesting a limited role for control measures targeting symptomatic individuals. Increased household transmission of Beta and Delta variants, likely contributed to successive waves, with >60% of individuals infected by the end of follow-up.

RESEARCH IN CONTEXT

Evidence before this study: Previous studies have generated wide-ranging estimates of the proportion of SARS-CoV-2 infections which are asymptomatic. A recent systematic review found that 20% (95% CI 3%-67%) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections remained asymptomatic throughout infection and that transmission from asymptomatic individuals was reduced. A systematic review and meta-analysis of 87 household transmission studies of SARS-CoV-2 found an estimated secondary attack rate of 19% (95% CI 16-22). The review also found that household secondary attack rates were increased from symptomatic index cases and that adults were more likely to acquire infection. As of December 2021, South Africa experienced three waves of SARS-CoV-2 infections; the second and third waves were associated with circulation of Beta and Delta variants respectively. SARS-CoV-2 vaccines became available in February 2021, but uptake was low in study sites reaching 5% fully vaccinated at the end of follow up. Studies to quantify the burden of asymptomatic infections, symptomatic fraction, reinfection frequency, duration of shedding and household transmission of SARS-CoV-2 from asymptomatically infected individuals have mostly been conducted as part of outbreak investigations or in specific settings. Comprehensive systematic community studies of SARS-CoV-2 burden and transmission including for the Beta and Delta variants are lacking, especially in low vaccination settings.Added value of this study: We conducted a unique detailed COVID-19 household cohort study over a 13 month period in South Africa, with real time reverse transcriptase polymerase chain reaction (rRT-PCR) testing twice a week irrespective of symptoms and bimonthly serology. By the end of the study in August 2021, 749 (62%) of 1200 individuals from 222 randomly sampled households in a rural and an urban community in South Africa had at least one confirmed SARS-CoV-2 infection, detected on rRT-PCR and/or serology, and 12% (87/749) experienced reinfection. Symptom data were analysed for 662 rRT-PCR-confirmed infection episodes that occurred >14 days after the start of follow-up (of a total of 718 rRT-PCR-confirmed episodes), of these, 15% (n=97) were associated with one or more symptoms. Among symptomatic indvidiausl, 9% (n=9) were hospitalised and 2% (n=2) died. Ninety percent (200/222) of included households, had one or more individual infected with SARS-CoV-2 on rRT-PCR and/or serology within the household. SARS-CoV-2 infected index cases transmitted the infection to 25% (213/856) of susceptible household contacts. Index case ribonucleic acid (RNA) viral load proxied by rRT-PCR cycle threshold value was strongly predictive of household transmission. Presence of symptoms in the index case was not associated with household transmission. Household transmission was four times greater from index cases infected with Beta variant and fifteen times greater from index cases infected with Delta variant compared to wild-type infection. Attack rates were highest in individuals aged 13-18 years and individuals in this age group were more likely to experience repeat infections and to acquire SARS-CoV-2 infection within households. People living with HIV (PLHIV) who were not virally supressed were more likely to develop symptomatic illness when infected with SARS-CoV-2, and shed SARS-CoV-2 for longer when compared to HIV-uninfected individuals.Implications of all the available evidence: We found a high rate of SARS-CoV-2 infection in households in a rural community and an urban community in South Africa, with the majority of infections being asymptomatic in individuals of all ages. Asymptomatic individuals transmitted SARS-CoV-2 at similar levels to symptomatic individuals suggesting that interventions targeting symptomatic individuals such as symptom-based testing and contact tracing of individuals tested because they report symptoms may have a limited impact as control measures. Increased household transmission of Beta and Delta variants, likely contributed to recurrent waves of COVID-19, with >60% of individuals infected by the end of follow-up. Higher attack rates, reinfection and acquisition in adolescents and prolonged SARS-CoV-2 shedding in PLHIV who were not virally suppressed suggests that prioritised vaccination of individuals in these groups could impact community transmission.

Under-diagnosis of SARS-CoV-2 infections among children aged 0-15 years, a nationwide seroprevalence study, Israel, January 2020 to March 2021

Until recently, children and adolescents were not eligible for COVID-19 vaccination. They may have been a considerable source of SARS-CoV-2 spread. We evaluated SARS-CoV-2 IgG antibody seroprevalence in Israeli children aged 0–15 years from January 2020 to March 2021. Seropositivity was 1.8–5.5 times higher than COVID-19 incidence rates based on PCR testing. We found that SARS-CoV-2 infection among children is more prevalent than previously thought and emphasise the importance of seroprevalence studies to accurately estimate exposure.

Introduction and expansion of the SARS-CoV-2 B.1.1.7 variant and reinfections in Qatar: A nationally representative cohort study

BACKGROUND

The epidemiology of the SARS-CoV-2 B.1.1.7 (or Alpha) variant is insufficiently understood. This study's objective was to describe the introduction and expansion of this variant in Qatar and to estimate the efficacy of natural infection against reinfection with this variant.

METHODS AND FINDINGS

Reinfections with the B.1.1.7 variant and variants of unknown status were investigated in a national cohort of 158,608 individuals with prior PCR-confirmed infections and a national cohort of 42,848 antibody-positive individuals. Infections with B.1.1.7 and variants of unknown status were also investigated in a national comparator cohort of 132,701 antibody-negative individuals. B.1.1.7 was first identified in Qatar on 25 December 2020. Sudden, large B.1.1.7 epidemic expansion was observed starting on 18 January 2021, triggering the onset of epidemic's second wave, 7 months after the first wave. B.1.1.7 was about 60% more infectious than the original (wild-type) circulating variants. Among persons with a prior PCR-confirmed infection, the efficacy of natural infection against reinfection was estimated to be 97.5% (95% CI: 95.7% to 98.6%) for B.1.1.7 and 92.2% (95% CI: 90.6% to 93.5%) for variants of unknown status. Among antibody-positive persons, the efficacy of natural infection against reinfection was estimated to be 97.0% (95% CI: 92.5% to 98.7%) for B.1.1.7 and 94.2% (95% CI: 91.8% to 96.0%) for variants of unknown status. A main limitation of this study is assessment of reinfections based on documented PCR-confirmed reinfections, but other reinfections could have occurred and gone undocumented.

CONCLUSIONS

In this study, we observed that introduction of B.1.1.7 into a naïve population can create a major epidemic wave, but natural immunity in those previously infected was strongly associated with limited incidence of reinfection by B.1.1.7 or other variants.

Model-based assessment of SARS-CoV-2 Delta variant transmission dynamics within partially vaccinated K-12 school populations

BACKGROUND

We examined school reopening policies amidst ongoing transmission of the highly transmissible Delta variant, accounting for vaccination among individuals ≥12 years.

METHODS

We collected data on social contacts among school-aged children in the California Bay Area and developed an individual-based transmission model to simulate transmission of the Delta variant of SARS-CoV-2 in schools. We evaluated the additional infections in students and teachers/staff resulting over a 128-day semester from in-school instruction compared to remote instruction when various NPIs (mask use, cohorts, and weekly testing of students/teachers) were implemented, across various community-wide vaccination coverages (50%, 60%, 70%), and student (≥12 years) and teacher/staff vaccination coverages (50% - 95%).

FINDINGS

At 70% vaccination coverage, universal masking reduced infections by >57% among students. Masking plus 70% vaccination coverage enabled achievement of <50 excess cases per 1,000 students/teachers, but stricter risk tolerances, such as <25 excess infections per 1,000 students/teachers, required a cohort approach in elementary and middle school populations. In the absence of NPIs, increasing the vaccination coverage of community members from 50% to 70% or elementary teachers from 70% to 95% reduced the excess rate of infection among elementary school students attributable to school transmission by 24% and 37%, respectively.

INTERPRETATIONS

Amidst Delta variant circulation, we found that schools are not inherently low risk, yet can be made so with high community vaccination coverages and masking. Vaccination of adults protects unvaccinated children.

FUNDING

National Science Foundation grant no. 2032210; National Institutes of Health grant nos. R01AI125842 and R01AI148336; MIDAS Coordination Center (MIDASSUP2020-4).

SARS-CoV-2 transmission across age groups in France and implications for control

The shielding of older individuals has been proposed to limit COVID-19 hospitalizations while relaxing general social distancing in the absence of vaccines. Evaluating such approaches requires a deep understanding of transmission dynamics across ages. Here, we use detailed age-specific case and hospitalization data to model the rebound in the French epidemic in summer 2020, characterize age-specific transmission dynamics and critically evaluate different age-targeted intervention measures in the absence of vaccines. We find that while the rebound started in young adults, it reached individuals aged ≥80 y.o. after 4 weeks, despite substantial contact reductions, indicating substantial transmission flows across ages. We derive the contribution of each age group to transmission. While shielding older individuals reduces mortality, it is insufficient to allow major relaxations of social distancing. When the epidemic remains manageable (R close to 1), targeting those most contributing to transmission is better than shielding at-risk individuals. Pandemic control requires an effort from all age groups.

Age-dependent effects on infectivity and susceptibility to SARS-CoV-2 infection: results from nationwide contact tracing data in Greece

BACKGROUND

Understanding the factors that affect the transmissibility of SARS-CoV-2 remains important to keep transmission low and maximize the health benefits of vaccination. We assessed the factors associated with the transmissibility of SARS-CoV-2 based on contact tracing data.

METHODS

From 1 October to 9 December 2020, 29,385 laboratory-confirmed SARS-CoV-2 cases (index cases, i.e. the first identified laboratory-confirmed cases or with the earliest symptom onset in a setting) and 64,608 traced contacts were identified in Greece. We assessed the prevalence of symptoms in cases, calculated secondary attack rates and assessed factors associated with infectivity and susceptibility to infection.

RESULTS

There were 11,232 contacts secondarily infected (secondary attack rate: 17.4%, 95% CI:17.0-17.8). Contacts aged 0-11 and 12-17 years were less susceptible to infection than adults 65 years or older (odds ratio (OR) [95% CI]: 0.28 [0.26-0.32] and 0.44 [0.40-0.49], respectively). Index cases aged 65 years or older were more likely to infect their contacts than other adults or children/adolescents. The odds of infection [95% CI] were higher in contacts exposed within the household (1.71 [1.59-1.85] vs. other) and in cases with cough (1.17 [1.11-1.25] vs. no cough). There was an interaction between the age of the index and the age of the contact with contacts 65 years or older having a higher probability of infection when exposed to cases of similar age than to children.

CONCLUSIONS

Our findings highlight the role of age and age mixing in infectivity and susceptibility to SARS-CoV-2 infection. Precautions are necessary for individuals 65 or older as they have higher infectivity and susceptibility in contact with their peers.

Using secondary cases to characterize the severity of an emerging or re-emerging infection

The methods to ascertain cases of an emerging infectious disease are typically biased toward cases with more severe disease, which can bias the average infection-severity profile. Here, we conducted a systematic review to extract information on disease severity among index cases and secondary cases identified by contact tracing of index cases for COVID-19. We identified 38 studies to extract information on measures of clinical severity. The proportion of index cases with fever was 43% higher than for secondary cases. The proportion of symptomatic, hospitalized, and fatal illnesses among index cases were 12%, 126%, and 179% higher than for secondary cases, respectively. We developed a statistical model to utilize the severity difference, and estimate 55% of index cases were missed in Wuhan, China. Information on disease severity in secondary cases should be less susceptible to ascertainment bias and could inform estimates of disease severity and the proportion of missed index cases.

[SARS-CoV-2 incidence, transmission, and containment measures in daycare centers during the COVID-19 pandemic-findings from the Corona Daycare Study]

Hintergrund

Kindertageseinrichtungen (Kitas) spielen eine wichtige gesellschaftspolitische Rolle; gleichzeitig begünstigt der enge Kontakt der Kinder in Kitagruppen untereinander und mit Beschäftigten die Übertragung von Infektionen. In der COVID-19-Pandemie ergaben sich die Fragen, wie Infektionsgeschehen in Kitas verlaufen, welche Rolle Kitakinder in der Pandemie spielen und welche Schutz- und Hygienemaßnahmen in Kitas umgesetzt werden. Von 06/2020 bis 12/2021 wird die „Corona-KiTa-Studie“ durchgeführt, in der pädagogische und infektionsepidemiologische Themen gemeinsam bearbeitet werden.

Methoden

In der Studie werden Daten aus unterschiedlichen Quellen erhoben. Es werden amtliche Meldedaten sowie wöchentliche Angaben von Kitas im sog. KiTa-Register kontinuierlich ausgewertet. Zudem werden SARS-CoV-2-Ausbrüche in Kitas vor Ort durch wiederholte Probengewinnung und Befragungen untersucht.

Ergebnisse

Das SARS-CoV-2-Infektionsgeschehen in Kitas bzw. bei Kindern im Kitaalter war von 03/2020 bis 05/2021 sehr dynamisch. In der 2. und 3. Pandemiewelle stiegen SARS-CoV-2-Ausbrüche in Kitas deutlich an, begleitet von einer erheblichen Zunahme an Kita- und Gruppenschließungen. Zuletzt erhöhte sich der Anteil der betroffenen Kinder bei den Ausbrüchen kontinuierlich. Allerdings ergab die erste Untersuchung von SARS-CoV-2-Ausbrüchen (n = 28), dass bei kindlichen Indexfällen im Schnitt nur ein Bruchteil der Kitakontakte (6,8 %) angesteckt wurde. Die Übertragungshäufigkeiten unterschieden sich zwischen einzelnen Kitas deutlich.

Diskussion

Die Zusammenführung von regelmäßig erhobenen Melde- und Befragungsdaten sowie Ausbruchsuntersuchungen ermöglicht ein vielschichtiges Monitoring des Infektionsgeschehens in Kitas, dessen Ergebnisse in Empfehlungen für Public-Health-Maßnahmen einfließen können.

Children and Adults in a Household Cohort Study Have Robust Longitudinal Immune Responses Following SARS-CoV-2 Infection or Exposure

Children have reduced severity of COVID-19 compared to adults and typically have mild or asymptomatic disease. The immunological mechanisms underlying these age-related differences in clinical outcomes remain unexplained. Here, we quantify 23 immune cell populations in 141 samples from children and adults with mild COVID-19 and their PCR-negative close household contacts at acute and convalescent time points. Children with COVID-19 displayed marked reductions in myeloid cells during infection, most prominent in children under the age of five. Recovery from infection in both children and adults was characterised by the generation of CD8 T_CM and CD4 T_CM up to 9 weeks post infection. SARS-CoV-2-exposed close contacts also had immunological changes over time despite no evidence of confirmed SARS-CoV-2 infection on PCR testing. This included an increase in low-density neutrophils during convalescence in both exposed children and adults, as well as increases in CD8 T_CM and CD4 T_CM in exposed adults. In comparison to children with other common respiratory viral infections, those with COVID-19 had a greater change in innate and T cell-mediated immune responses over time. These findings provide new mechanistic insights into the immune response during and after recovery from COVID-19 in both children and adults.

Coronavirus Disease 2019 Cluster Originating in a Primary School Teachers' Room in Japan

BACKGROUND

School closures are a subject of debate during the present coronavirus disease 2019 (COVID-19) pandemic. Because children are not the main driver of COVID-19 transmission in the community, school education must be prioritized in conjunction with appropriate infection prevention and control measures, as determined by local COVID-19 incidence.

METHODS

We investigated the causes and transmission routes of a primary school cluster of COVID-19 that occurred during November and December 2020 in Niigata, Japan.

RESULTS

In the cluster, the virus spread among teachers, then from teachers to students, and then to their family members. This primary school cluster comprised 26 infected patients and included teachers (13/33, 39%), students (9/211, 4%), and family members (4/65, 6%). The secondary attack rate from the 3 index teachers to the remaining 30 teachers was 33%; however, the rate to students was only 4%. Factors contributing to cluster formation include the fact that 2 of the index teachers continued working while symptomatic and that the environment and infection prevention measures in the teachers' room were inadequate.

CONCLUSIONS

To open schools safely and without interruption, adequate measures to prevent COVID-19 infection in schools should be emphasized not only for children but also for teachers and their environment.

Association of Age and Pediatric Household Transmission of SARS-CoV-2 Infection

Importance

As a result of low numbers of pediatric cases early in the COVID-19 pandemic, pediatric household transmission of SARS-CoV-2 remains an understudied topic.

Objective

To determine whether there are differences in the odds of household transmission by younger children compared with older children.

Design, Setting, and Participants

This population-based cohort study took place between June 1 and December 31, 2020, in Ontario, Canada. Private households in which the index case individual of laboratory-confirmed SARS-CoV-2 infection was younger than 18 years were included. Individuals were excluded if they resided in apartments missing suite information, in households with multiple index cases, or in households where the age of the index case individual was missing.

Exposures

Age group of pediatric index cases categorized as 0 to 3, 4 to 8, 9 to 13, and 14 to 17 years.

Main Outcomes and Measures

Household transmission, defined as households where at least 1 secondary case occurred 1 to 14 days after the pediatric index case.

Results

A total of 6280 households had pediatric index cases, and 1717 households (27.3%) experienced secondary transmission. The mean (SD) age of pediatric index case individuals was 10.7 (5.1) years and 2863 (45.6%) were female individuals. Children aged 0 to 3 years had the highest odds of transmitting SARS-CoV-2 to household contacts compared with children aged 14 to 17 years (odds ratio, 1.43; 95% CI, 1.17-1.75). This association was similarly observed in sensitivity analyses defining secondary cases as 2 to 14 days or 4 to 14 days after the index case and stratified analyses by presence of symptoms, association with a school/childcare outbreak, or school/childcare reopening. Children aged 4 to 8 years and 9 to 13 years also had increased odds of transmission (aged 4-8 years: odds ratio, 1.40; 95% CI, 1.18-1.67; aged 9-13 years: odds ratio, 1.13; 95% CI, 0.97-1.32).

Conclusions and Relevance

This study suggests that younger children may be more likely to transmit SARS-CoV-2 infection compared with older children, and the highest odds of transmission was observed for children aged 0 to 3 years. Differential infectivity of pediatric age groups has implications for infection prevention within households, as well as schools/childcare, to minimize risk of household secondary transmission. Additional population-based studies are required to establish the risk of transmission by younger pediatric index cases.

Factors affecting the acceptability of COVID-19 vaccine in the postpartum period

BACKGROUND

Coronavirus disease 2019 (COVID-19) has spread rapidly around the world, causing massive morbidity and mortality. Vaccination during puerperium protects both the mother and the newborn and is important to keep the pandemic under control.

METHODS

Women who gave birth at Ankara City Hospital between February 11, 2021 and March 21, 2021 were included. Data were collected through a face-to-face questionnaire.

RESULTS

We asked 412 postpartum women were surveyed about their acceptance of the COVID-19 vaccine; 137 (33.3%) of them wanted to be vaccinated, while 275 (66.7%) of them did not want to be vaccinated. Reasons for vaccination rejection; 209 (76%) of them stated that there was not enough information about the safety of the vaccine for the postpartum period, and 89 (32.4%) of them thought that the vaccine would not be effective for the disease. Three of the answers in the survey were found significantly different in high-risk pregnancy (HRP) group compared to low-risk pregnancy (LRP) group; 1) Having their babies to be vaccinated, 2) To be vaccinated if it will be recommended to the puerperal women, and 3) Feeling anxious about being infected by SARS-CoV-2 (p < .05).

CONCLUSIONS

Health authorities recommend the COVID-19 vaccine to breastfeeding mothers. However, a relatively low vaccination acceptance rate was observed in the present study. For newly developed vaccines, concern over vaccine safety is the biggest obstacle to vaccine administration. Therefore, the reasons that influence acceptance or refusal of vaccines are important for developing targeted communication strategies and healthcare policies.

Coronavirus disease 2019 in children

PURPOSE OF REVIEW

Over the course of the coronavirus disease 2019 (COVID-19) pandemic, it has become clear that the clinical features, epidemiology, and outcomes of COVID-19 are distinct in children relative to adults. In this review, we will present recent pediatric studies informing our current understanding of COVID-19 in children, and review pediatric considerations surrounding disease transmission, currently available therapies, and vaccination.

RECENT FINDINGS

Recent studies have shed light on the clinical epidemiology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in children, identifying a high prevalence of asymptomatic and mild infections, with severe COVID-19 infrequently reported. Several adult clinical trials have informed the use of remdesivir, anti-SARS-CoV-2 monoclonal antibodies, dexamethasone, and tocilizumab in the management of COVID-19. Associations between underlying comorbid medical conditions and severe outcomes, as well as transmission dynamics of SARS-CoV-2 in children, are complex and warrant further study. Finally, highly efficacious vaccines are available for adults and adolescents, with pediatric trials ongoing.

SUMMARY

Children generally fare well with acute COVID-19 infection, though critical illness is possible. Future research should focus on clarifying the role of children in SARS-CoV-2 transmission and optimal prevention strategies, particularly in the school setting, as well as evaluating pediatric vaccine candidates.

Pediatric Household Transmission of Severe Acute Respiratory Coronavirus-2 Infection-Los Angeles County, December 2020 to February 2021

This brief report presents transmission rates from a prospective study of 15 households with pediatric index cases of severe acute respiratory coronavirus-2 in Los Angeles County from December 2020 to February 2021. Our findings support ongoing evidence that transmission from pediatric index cases to household contacts is frequent but can be mitigated with practicing well-documented control measures at home, including isolation, masking and good hand hygiene.

Comparison of Symptoms and RNA Levels in Children and Adults With SARS-CoV-2 Infection in the Community Setting

Importance

The association between COVID-19 symptoms and SARS-CoV-2 viral levels in children living in the community is not well understood.

Objective

To characterize symptoms of pediatric COVID-19 in the community and analyze the association between symptoms and SARS-CoV-2 RNA levels, as approximated by cycle threshold (Ct) values, in children and adults.

Design, Setting, and Participants

This cross-sectional study used a respiratory virus surveillance platform in persons of all ages to detect community COVID-19 cases from March 23 to November 9, 2020. A population-based convenience sample of children younger than 18 years and adults in King County, Washington, who enrolled online for home self-collection of upper respiratory samples for SARS-CoV-2 testing were included.

Exposures

Detection of SARS-CoV-2 RNA by reverse transcription-polymerase chain reaction (RT-PCR) from participant-collected samples.

Main Outcomes and Measures

RT-PCR-confirmed SARS-CoV-2 infection, with Ct values stratified by age and symptoms.

Results

Among 555 SARS-CoV-2-positive participants (mean [SD] age, 33.7 [20.1] years; 320 were female [57.7%]), 47 of 123 children (38.2%) were asymptomatic compared with 31 of 432 adults (7.2%). When symptomatic, fewer symptoms were reported in children compared with adults (mean [SD], 1.6 [2.0] vs 4.5 [3.1]). Symptomatic individuals had lower Ct values (which corresponded to higher viral RNA levels) than asymptomatic individuals (adjusted estimate for children, -3.0; 95% CI, -5.5 to -0.6; P = .02; adjusted estimate for adults, -2.9; 95% CI, -5.2 to -0.6; P = .01). The difference in mean Ct values was neither statistically significant between symptomatic children and symptomatic adults (adjusted estimate, -0.7; 95% CI, -2.2 to 0.9; P = .41) nor between asymptomatic children and asymptomatic adults (adjusted estimate, -0.6; 95% CI, -4.0 to 2.8; P = .74).

Conclusions and Relevance

In this community-based cross-sectional study, SARS-CoV-2 RNA levels, as determined by Ct values, were significantly higher in symptomatic individuals than in asymptomatic individuals and no significant age-related differences were found. Further research is needed to understand the role of SARS-CoV-2 RNA levels and viral transmission.

Transmission of SARS-CoV-2 After COVID-19 Screening and Mitigation Measures for Primary School Children Attending School in Liège, Belgium

IMPORTANCE

Recent data suggest a relatively low incidence of COVID-19 among children. The possible role that children attending primary school may play in the transmission of SARS-CoV-2 remains poorly understood.

OBJECTIVE

To gain a better understanding of the possible role of children in the transmission of SARS-CoV-2.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study was conducted from September 21 to December 31, 2020, in a primary school in Liège, Belgium, among a volunteer sample of 181 children, parents, and school employees.

EXPOSURES

Participants were tested for SARS-CoV-2 infection once a week for 15 weeks through throat washing, performed with 5 mL of saline and collected in a sterile tube after approximately 30 seconds of gargling. Quantitative reverse transcription-polymerase chain reaction was performed to detect SARS-CoV-2 infection.

MAIN OUTCOMES AND MEASURES

In case of test positivity, participants were asked to complete a questionnaire aimed at determining the timing of symptom onset and symptom duration. SARS-CoV-2 genetic sequencing was also performed. Confirmed cases were linked based on available information on known contacts and viral sequences.

RESULTS

A total of 181 individuals participated in this study, including 63 children (34 girls [54.0%]; mean [SD] age, 8.6 [1.9] years [range, 5-13 years]) and 118 adults (75 women [63.6%]; mean [SD] age, 42.5 [5.7] years [range, 30-59 years]). Forty-five individuals (24.9%) tested positive: 13 children (20.6%; 95% CI, 10.6%-30.6%) and 32 adults (27.1%; 95% CI, 19.1%-35.7%) (P = .34). Children were more often asymptomatic compared with adults (6 [46.2%; 95% CI, 19.1%-73.3%] vs 4 of 31 [12.9%; 95% CI, 1.3%-24.5%]; P = .04). The median duration of symptoms was shorter in children than in adults (0.00 days [IQR, 0.00-1.00 days] vs 15.00 days [IQR, 7.00-22.00 days]). A reconstruction of the outbreak revealed that most transmission events occurred between teachers and between children within the school. Of the observed household transmission events, most seemed to have originated from a child or teacher who acquired the infection at school.

CONCLUSIONS AND RELEVANCE

Despite the implementation of several mitigation measures, the incidence of COVID-19 among children attending primary school in this study was comparable to that observed among teachers and parents. Transmission tree reconstruction suggests that most transmission events originated from within the school. Additional measures should be considered to reduce the transmission of SARS-CoV-2 at school, including intensified testing.

Low SARS-CoV-2 seroprevalence but high perception of risk among healthcare workers at children's hospital before second pandemic wave in Germany

BACKGROUND

Healthcare workers are considered a particularly high-risk group during the coronavirus disease 2019 (COVID-19) pandemic. Healthcare workers in paediatrics are a unique subgroup: they come into frequent contact with children, who often experience few or no symptoms when infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and, therefore, may transmit the disease to unprotected staff. In Germany, no studies exist evaluating the risk of COVID-19 to healthcare workers in paediatric institutions.

METHODS

We tested the staff at a large children's hospital in Germany for immunoglobulin (Ig) G antibodies against the nucleocapsid protein of SARS-CoV-2 in a period between the first and second epidemic wave in Germany. We used a questionnaire to assess each individual's exposure risk and his/her own perception of having already been infected with SARS-CoV-2.

RESULTS

We recruited 619 participants from all sectors, clinical and non-clinical, constituting 70% of the entire staff. The seroprevalence of SARS-CoV-2 antibodies was 0.325% (95% confidence interval 0.039-1.168). Self-perceived risk of a previous SARS-CoV-2 infection decreased with age (odds ratio, 0.81; 95% confidence interval, 0.70-0.93). Having experienced symptoms more than doubled the odds of a high self-perceived risk (odds ratio, 2.18; 95% confidence interval, 1.59-3.00). There was no significant difference in self-perceived risk between men and women.

CONCLUSIONS

Seroprevalence was low among healthcare workers at a large children's hospital in Germany before the second epidemic wave, and it was far from a level that confers herd immunity. Self-perceived risk of infection is often overestimated.

Pediatric COVID-19: Immunopathogenesis, Transmission and Prevention

Children are unique in the context of the COVID-19 pandemic. Overall, SARS-CoV-2 has a lower medical impact in children as compared to adults. A higher proportion of children than adults remain asymptomatic following SARS-CoV-2 infection and severe disease and death are also less common. This relative resistance contrasts with the high susceptibility of children to other respiratory tract infections. The mechanisms involved remain incompletely understood but could include the rapid development of a robust innate immune response. On the other hand, children develop a unique and severe complication, named multisystem inflammatory syndrome in children, several weeks after the onset of symptoms. Although children play an important role in the transmission of many pathogens, their contribution to the transmission of SARS-CoV-2 appears lower than that of adults. These unique aspects of COVID-19 in children must be considered in the benefit-risk analysis of vaccination. Several COVID-19 vaccines have been authorized for emergency use in adolescents and clinical studies are ongoing in children. As the vaccination of adolescents is rolled out in several countries, we shall learn about the impact of this strategy on the health of children and on transmission within communities.

Pooled RT-qPCR testing for SARS-CoV-2 surveillance in schools - a cluster randomised trial

BACKGROUND

The extent to which children and adolescents contribute to SARS-CoV-2 transmission remains not fully understood. Novel high-capacity testing methods may provide real-time epidemiological data in educational settings helping to establish a rational approach to prevent and minimize SARS-CoV-2 transmission. We investigated whether pooling of samples for SARS-CoV-2 detection by RT-qPCR is a sensitive and feasible high-capacity diagnostic strategy for surveillance of SARS-CoV-2 infections in schools.

METHODS

In this study, students and school staff of 14 educational facilities in Germany were tested sequentially between November 9 and December 23, 2020, two or three times per week for at least three consecutive weeks. Participants were randomized for evaluation of two different age adjusted swab sampling methods (oropharyngeal swabs or buccal swabs compared to saliva swabs using a 'lolli method'). Swabs were collected and pooled for SARS-CoV-2 RT-qPCR. Individuals of positive pooled tests were retested by RT-qPCR the same or the following day. Positive individuals were quarantined while the SARS-CoV-2 negative individuals remained in class with continued pooled RT-qPCR surveillance. The study is registered with the German Clinical Trials register (registration number: DRKS00023911).

FINDINGS

5,537 individuals were eligible and 3970 participants were enroled and included in the analysis. In students, a total of 21,978 swabs were taken and combined in 2218 pooled RT-qPCR tests. We detected 41 positive pooled tests (1·8%) leading to 36 SARS-CoV-2 cases among students which could be identified by individual re-testing. The cumulative 3-week incidence for primary schools was 564/100,000 (6/1064, additionally 1 infection detected in week 4) and 1249/100,000 (29/2322) for secondary schools. In secondary schools, there was no difference in the number of SARS-CoV-2 positive students identified from pooled oropharyngeal swabs compared to those identified from pooled saliva samples (lolli method) (14 vs. 15 cases; 1·3% vs. 1·3%; OR 1.1; 95%-CI 0·5-2·5). A single secondary school accounted for 17 of 36 cases (47%) indicating a high burden of asymptomatic prevalent SARS-CoV-2 cases in the respective school and community.

INTERPRETATION

In educational settings, SARS-CoV-2 screening by RT-qPCR-based pooled testing with easily obtainable saliva samples is a feasible method to detect incident cases and observe transmission dynamics.

FUNDING

Federal Ministry of education and research (BMBF; Project B-FAST in "NaFoUniMedCovid19"; registration number: 01KX2021).

A Longitudinal, Clinical, and Spatial Epidemiologic Analysis of a Large COVID-19 Long-Term Care Home Outbreak

Objectives

COVID-19 has had devastating effects on long-term care homes across much of the world, and especially within Canada, with more than 50% of the mortality from COVID-19 in 2020 in these homes. Understanding the way in which the virus spreads within these homes is critical to preventing further outbreaks.

Design

Retrospective chart review.

Settings and Participants

Long-term care home residents and staff in Ontario, Canada.

Methods

We conducted a longitudinal study of a large long-term care home COVID-19 outbreak in Ontario, Canada, using electronic medical records, public health records, staff assignments, and resident room locations to spatially map the outbreak through the facility.

Results

By analyzing the outbreak longitudinally, we were able to draw 3 important conclusions: (1) 84.5% had typical COVID-19 symptoms and only 15.5% of residents had asymptomatic infection; (2) there was a high attack rate of 85.8%, which appeared to be explained by a high degree of interconnectedness within the home exacerbated by staffing shortages; and (3) clustering of infections within multibedded rooms was common.

Conclusion and Implications

Low rates of asymptomatic infection suggest that symptom-based screening in residents remains very important for detecting outbreaks, a high degree of interconnectedness explains the high attack rate, and there is a need for improved guidance for homes with multibedded rooms on optimizing resident room movement to mitigate spread of COVID-19 in long-term care homes.

Model-based assessment of SARS-CoV-2 Delta variant transmission dynamics within partially vaccinated K-12 school populations

BACKGROUND

We examined school reopening policies amidst rising transmission of the highly transmissible Delta variant, accounting for vaccination among individuals aged 12 years and older, with the goal of characterizing risk to students and teachers under various within-school non-pharmaceutical interventions (NPIs) combined with specific vaccination coverage levels.

METHODS

We developed an individual-based transmission model to simulate transmission of the Delta variant of SARS-CoV-2 among a synthetic population, representative of Bay Area cities. We parameterized the model using community contact rates from vaccinated households ascertained from a household survey of Bay Area families with children conducted between February - April, 2021.

INTERVENTIONS AND OUTCOMES

We evaluated the additional infections in students and teachers/staff resulting over a 128-day semester from in-school instruction compared to remote instruction when various NPIs (mask use, cohorts, and weekly testing of students/teachers) were implemented in schools, across various community-wide vaccination coverages (50%, 60%, 70%), and student (≥12 years) and teacher/staff vaccination coverages (50% - 95%). We quantified the added benefit of universal masking over masking among unvaccinated students and teachers, across varying levels of vaccine effectiveness (45%, 65%, 85%), and compared results between Delta and Alpha variant circulation.

RESULTS

The Delta variant sharply increases the risk of within-school COVID-transmission when compared to the Alpha variant. In our highest risk scenario (50% community and within-school vaccine coverage, no within-school NPIs, and predominant circulation of the Delta variant), we estimated that an elementary school could see 33-65 additional symptomatic cases of COVID-19 over a four-month semester (depending on the relative susceptibility of children <10 years). In contrast, under the Bay Area reopening plan (universal mask use, community and school vaccination coverage of 70%), we estimated excess symptomatic infection attributable to school reopening among 2.0-9.7% of elementary students (8-36 excess symptomatic cases per school over the semester), 3.0% of middle school students (13 cases per school) and 0.4% of high school students (3 cases per school). Excess rates among teachers attributable to reopening were similar. Achievement of lower risk tolerances, such as <5 excess infections per 1,000 students or teachers, required a cohort approach in elementary and middle school populations. In the absence of NPIs, increasing the vaccination coverage of community members from 50% to 70% or elementary teachers from 70% to 95% reduced the estimated excess rate of infection among elementary school students attributable to school transmission by 24% and 41%, respectively. We estimated that with 70% coverage of the eligible community and school population with a vaccine that is ≤65% effective, universal masking can avert more cases than masking of unvaccinated persons alone.

CONCLUSIONS

Amidst circulation of the Delta variant, our findings demonstrated that schools are not inherently low risk, yet can be made so with high community vaccination coverages and universal masking. Vaccination of adult community members and teachers protects unvaccinated elementary and middle school children. Elementary and middle schools that can support additional interventions, such as cohorts and testing, should consider doing so, particularly if additional studies find that younger children are equally as susceptible as adults to the Delta variant of SARS-CoV-2.

LIMITATIONS

We did not consider the effect of social distancing in classrooms, or variation in testing frequency, and considerable uncertainty remains in key transmission parameters.

A cross-sectional and prospective cohort study of the role of schools in the SARS-CoV-2 second wave in Italy

BACKGROUND

During COVID-19 pandemic, school closure has been mandated in analogy to its effect against influenza, but it is unclear whether schools are early COVID-19 amplifiers.

METHODS

We performed a cross-sectional and prospective cohort study in Italy during the second COVID-19 wave (from September 30, 2020 until at least February 28, 2021). We used databases from the Italian Ministry of Education, the Veneto region systems of SARS-CoV-2 cases notification and of schools' secondary cases tracing to compare SARS-CoV-2 incidence in students/school staff and general population and incidence across age groups. Number of tests, secondary infections by type of index case and ratio cases/ tests per school were estimated using an adjusted multivariable generalized linear regression model. Regional reproduction numbers Rt were estimated from Italian Civil Protection daily incidence data with a method of posterior distribution using a Markov Chain Monte Carlo algorithm.

FINDINGS

SARS-CoV-2 incidence among students was lower than in the general population. Secondary infections at school were <1%, and clusters of ≥2 secondary cases occurred in 5-7% of the analysed schools. Incidence among teachers was comparable to the population of similar age (P = 0.23). Secondary infections among teachers were rare, occurring more frequently when the index case was a teacher than a student (37% vs. 10%, P = 0.007). Before and around the date of school opening in Veneto, SARS-CoV-2 incidence grew maximally in 20-29- and 45-49-years old individuals, not among students. The lag between school opening dates in Italian regions and the increase in the regional COVID-19 Rt was not uniform. Finally, school closures in two regions where they were implemented before other measures did not affect Rt decrease.

INTERPRETATION

This analysis does not support a role for school opening as a driver of the second COVID-19 wave in Italy, a large European country with high SARS-CoV-2 incidence.

FUNDING

Fondazione MITE.

An examination of school reopening strategies during the SARS-CoV-2 pandemic

The SARS-CoV-2 pandemic led to closure of nearly all K-12 schools in the United States of America in March 2020. Although reopening K-12 schools for in-person schooling is desirable for many reasons, officials understand that risk reduction strategies and detection of cases are imperative in creating a safe return to school. Furthermore, consequences of reclosing recently opened schools are substantial and impact teachers, parents, and ultimately educational experiences in children. To address competing interests in meeting educational needs with public safety, we compare the impact of physical separation through school cohorts on SARS-CoV-2 infections against policies acting at the level of individual contacts within classrooms. Using an age-stratified Susceptible-Exposed-Infected-Removed model, we explore influences of reduced class density, transmission mitigation, and viral detection on cumulative prevalence. We consider several scenarios over a 6-month period including (1) multiple rotating cohorts in which students cycle through in-person instruction on a weekly basis, (2) parallel cohorts with in-person and remote learning tracks, (3) the impact of a hypothetical testing program with ideal and imperfect detection, and (4) varying levels of aggregate transmission reduction. Our mathematical model predicts that reducing the number of contacts through cohorts produces a larger effect than diminishing transmission rates per contact. Specifically, the latter approach requires dramatic reduction in transmission rates in order to achieve a comparable effect in minimizing infections over time. Further, our model indicates that surveillance programs using less sensitive tests may be adequate in monitoring infections within a school community by both keeping infections low and allowing for a longer period of instruction. Lastly, we underscore the importance of factoring infection prevalence in deciding when a local outbreak of infection is serious enough to require reverting to remote learning.

A guideline to limit indoor airborne transmission of COVID-19

The current revival of the American economy is being predicated on social distancing, specifically the Six-Foot Rule, a guideline that offers little protection from pathogen-bearing aerosol droplets sufficiently small to be continuously mixed through an indoor space. The importance of airborne transmission of COVID-19 is now widely recognized. While tools for risk assessment have recently been developed, no safety guideline has been proposed to protect against it. We here build on models of airborne disease transmission in order to derive an indoor safety guideline that would impose an upper bound on the "cumulative exposure time," the product of the number of occupants and their time in an enclosed space. We demonstrate how this bound depends on the rates of ventilation and air filtration, dimensions of the room, breathing rate, respiratory activity and face mask use of its occupants, and infectiousness of the respiratory aerosols. By synthesizing available data from the best-characterized indoor spreading events with respiratory drop size distributions, we estimate an infectious dose on the order of 10 aerosol-borne virions. The new virus (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) is thus inferred to be an order of magnitude more infectious than its forerunner (SARS-CoV), consistent with the pandemic status achieved by COVID-19. Case studies are presented for classrooms and nursing homes, and a spreadsheet and online app are provided to facilitate use of our guideline. Implications for contact tracing and quarantining are considered, and appropriate caveats enumerated. Particular consideration is given to respiratory jets, which may substantially elevate risk when face masks are not worn.

A guideline to limit indoor airborne transmission of COVID-19

The current revival of the American economy is being predicated on social distancing, specifically the Six-Foot Rule, a guideline that offers little protection from pathogen-bearing aerosol droplets sufficiently small to be continuously mixed through an indoor space. The importance of airborne transmission of COVID-19 is now widely recognized. While tools for risk assessment have recently been developed, no safety guideline has been proposed to protect against it. We here build on models of airborne disease transmission in order to derive an indoor safety guideline that would impose an upper bound on the "cumulative exposure time," the product of the number of occupants and their time in an enclosed space. We demonstrate how this bound depends on the rates of ventilation and air filtration, dimensions of the room, breathing rate, respiratory activity and face mask use of its occupants, and infectiousness of the respiratory aerosols. By synthesizing available data from the best-characterized indoor spreading events with respiratory drop size distributions, we estimate an infectious dose on the order of 10 aerosol-borne virions. The new virus (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) is thus inferred to be an order of magnitude more infectious than its forerunner (SARS-CoV), consistent with the pandemic status achieved by COVID-19. Case studies are presented for classrooms and nursing homes, and a spreadsheet and online app are provided to facilitate use of our guideline. Implications for contact tracing and quarantining are considered, and appropriate caveats enumerated. Particular consideration is given to respiratory jets, which may substantially elevate risk when face masks are not worn.

Age-dependent pathogenic characteristics of SARS-CoV-2 infection in ferrets

While the seroprevalence of SARS-CoV-2 in healthy people does not differ significantly among age groups, those aged 65 years or older exhibit strikingly higher COVID-19 mortality compared to younger individuals. To further understand differing COVID-19 manifestations in patients of different ages, three age groups of ferrets were infected with SARS-CoV-2. Although SARS-CoV-2 was isolated from all ferrets regardless of age, aged ferrets (≥ 3 years old) showed higher viral loads, longer nasal virus shedding, and more severe lung inflammatory cell infiltration and clinical symptoms compared to juvenile (≤ 6 months) and young adult (1-2 years) groups. Transcriptome analysis of aged ferret lungs revealed strong enrichment of gene sets related to type I interferon, activated T cells, and M1 macrophage responses, mimicking the gene expression profile of severe COVID-19 patients. Thus, SARS-CoV-2-infected aged ferrets highly recapitulate COVID-19 patients with severe symptoms and are useful for understanding age-associated infection, transmission, and pathogenesis of SARS-CoV-2.

Household SARS-CoV-2 transmission and children: a network prospective study

Background

The role of children in household transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains uncertain. Here, we describe the epidemiological and clinical characteristics of children with COVID-19 in Catalonia (Spain) and investigate the dynamics of household transmission.

Methods

Prospective, observational, multicenter study performed during summer and school periods (1 July-31 October, 2020), in which epidemiological and clinical features, and viral transmission dynamics were analyzed in COVID-19 patients <16 years. A pediatric index case was established when a child was the first individual infected within a household. Secondary cases were defined when another household member tested positive for SARS-CoV-2 before the child. The secondary attack rate (SAR) was calculated, and logistic regression was used to assess associations between transmission risk factors and SARS-CoV-2 infections.

Results

The study included 1040 COVID-19 patients <16 years. Almost half (47.2%) were asymptomatic, 10.8% had comorbidities, and 2.6% required hospitalization. No deaths were reported. Viral transmission was common among household members (62.3%). More than 70% (756/1040) of pediatric cases were secondary to an adult, whereas 7.7% (80/1040) were index cases. The SAR was significantly lower in households with COVID-19 pediatric index cases during the school period relative to summer (p=0.02), and when compared to adults (p=0.006). No individual or environmental risk factors associated with the SAR were identified.

Conclusions

Children are unlikely to cause household COVID-19 clusters or be major drivers of the pandemic even if attending school. Interventions aimed at children are expected to have a small impact on reducing SARS-CoV-2 transmission.

The Experience of Greece as a Model to Contain COVID-19 Infection Spread

The severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) emerged in late 2019 and has caused a pandemic known as corona virus disease 2019 (COVID-19), responsible for the death of more than 2 million people worldwide. The outbreak of COVID-19 has posed an unprecedented threat on human lives and public safety. The aim of this review is to describe key aspects of the bio-pathology of the novel disease, and discuss aspects of its spread, as well as targeted protective strategies that can help shape the outcome of the present and future health crises. Greece is used as a model to inhibit SARS-COV-2 spread, since it is one of the countries with the lowest fatality rates among nations of the European Union (E.U.), following two consecutive waves of COVID-19 pandemic. Furthermore, niche research technological approaches and scientific recommendations that emerged during the COVID-19 era are discussed.