SARS-CoV-2 transmission patterns in educational settings during the Alpha wave in Reggio-Emilia, Italy

Child Transmission of SARS-CoV-2 Throughout the Pandemic: An Updated Systematic Review and Meta-Analysis

BACKGROUND

This systematic review sought to characterize child-to-child and child-to-adult transmission of severe acute respiratory coronavirus 2 (SARS-CoV-2).

METHODS

A systematic review was conducted from April 1, 2021, to December 15, 2023, to estimate secondary attack rates (SARs) and secondary infections per index case (case rate) from index cases up to age 20 years. SAR and case rate were analyzed based on age, setting, country and variant prevalence. Meta-analysis was conducted on the SAR data.

RESULTS

Eighty-six studies were included, representing 33,674 index cases. The total pooled SAR was 0.11 (95% CI: 0.07-0.16); 0.05 (95% CI: 0.03-0.10) for child-to-child transmission and 0.15 (95% CI: 0.07-0.30) for child-to-adult transmission. Pooled SAR in households was 0.28 (95% CI: 0.24-0.34) and was 0.02 (95% CI: 0.01-0.04) in schools.

CONCLUSIONS

The role of children in SARS-CoV-2 transmission is small, particularly in schools. This work can help inform policies that effectively reduce transmission while minimizing adverse effects on children.

A modeling study to define guidelines for antigen screening in schools and workplaces to mitigate COVID-19 outbreaks

BACKGROUND

In-person interaction offers invaluable benefits to people. To guarantee safe in-person activities during a COVID-19 outbreak, effective identification of infectious individuals is essential. In this study, we aim to analyze the impact of screening with antigen tests in schools and workplaces on identifying COVID-19 infections.

METHODS

We assess the effectiveness of various screening test strategies with antigen tests in schools and workplaces through quantitative simulations. The primary outcome of our analyses is the proportion of infected individuals identified. The transmission process at the population level is modeled using a deterministic compartmental model. Infected individuals are identified through screening tests or symptom development. The time-varying sensitivity of antigen tests and infectiousness is determined by a viral dynamics model. Screening test strategies are characterized by the screening schedule, sensitivity of antigen tests, screening duration, timing of screening initiation, and available tests per person.

RESULTS

Here, we show that early and frequent screening is the key to maximizing the effectiveness of the screening program. For example, 44.5% (95% CI: 40.8-47.5) of infected individuals are identified by daily testing, whereas it is only 33.7% (95% CI: 30.5-37.3) when testing is performed at the end of the program duration. If high sensitivity antigen tests (Detection limit: 6.3 × 10 4 copies/mL) are deployed, it reaches 69.3% (95% CI: 66.5-72.5).

CONCLUSIONS

High sensitivity antigen tests, high frequency screening tests, and immediate initiation of screening tests are important to safely restart educational and economic activities in-person. Our computational framework is useful for assessing screening programs by incorporating situation-specific factors.

Vaccine-induced reduction of COVID-19 clusters in school settings in Japan during the epidemic wave caused by B.1.1.529 (Omicron) BA.2, 2022

Clusters of COVID-19 in high-risk settings, such as schools, have been deemed a critical driving force of the major epidemic waves at the societal level. In Japan, the vaccination coverage among students remained low up to early 2022, especially for 5-11-year-olds. The vaccination of the student population only started in February 2022. Given this background and considering that vaccine effectiveness against school transmission has not been intensively studied, this paper proposes a mathematical model that links the occurrence of clustering to the case count among populations aged 0-19, 20-59, and 60+ years of age. We first estimated the protected (immune) fraction of each age group either by infection or vaccination and then linked the case count in each age group to the number of clusters via a time series regression model that accounts for the time-varying hazard of clustering per infector. From January 3 to May 30, 2022, there were 4,722 reported clusters in school settings. Our model suggests that the immunity offered by vaccination averted 226 (95% credible interval: 219-232) school clusters. Counterfactual scenarios assuming elevated vaccination coverage with faster roll-out reveal that additional school clusters could have been averted. Our study indicates that even relatively low vaccination coverage among students could substantially lower the risk of clustering through vaccine-induced immunity. Our results also suggest that antigenically updated vaccines that are more effective against the variant responsible for the ongoing epidemic may greatly help decrease not only the incidence but also the unnecessary loss of learning opportunities among school-age students.

Effect of an enhanced public health contact tracing intervention on the secondary transmission of SARS-CoV-2 in educational settings: The four-way decomposition analysis

Background

The aim of our study was to test the hypothesis that the community contact tracing strategy of testing contacts in households immediately instead of at the end of quarantine had an impact on the transmission of SARS-CoV-2 in schools in Reggio Emilia Province.

Methods

We analysed surveillance data on notification of COVID-19 cases in schools between 1 September 2020 and 4 April 2021. We have applied a mediation analysis that allows for interaction between the intervention (before/after period) and the mediator.

Results

Median tracing delay decreased from 7 to 3.1 days and the percentage of the known infection source increased from 34-54.8% (incident rate ratio-IRR 1.61 1.40-1.86). Implementation of prompt contact tracing was associated with a 10% decrease in the number of secondary cases (excess relative risk -0.1 95% CI -0.35-0.15). Knowing the source of infection of the index case led to a decrease in secondary transmission (IRR 0.75 95% CI 0.63-0.91) while the decrease in tracing delay was associated with decreased risk of secondary cases (1/IRR 0.97 95% CI 0.94-1.01 per one day of delay). The direct effect of the intervention accounted for the 29% decrease in the number of secondary cases (excess relative risk -0.29 95%-0.61 to 0.03).

Conclusions

Prompt contact testing in the community reduces the time of contact tracing and increases the ability to identify the source of infection in school outbreaks. Although there are strong reasons for thinking it is a causal link, observed differences can be also due to differences in the force of infection and to other control measures put in place.

Funding

This project was carried out with the technical and financial support of the Italian Ministry of Health - CCM 2020 and Ricerca Corrente Annual Program 2023.