Author: Christine Salvatore MD, MS. Associate Professor of Clinical Pediatrics, Weill Cornell Medical College, Cornell University

Reviewer: Kristin Moffit, MD. Associate Physician in Pediatrics, Division of Infectious Diseases, Assistant Professor of Pediatrics, Harvard Medical School

COVID-19 in Children and the Dynamics of Infection in Families

Klara M. Posfay-Barbe, Noemie Wagner, Magali Gauthey et al. Pediatrics July 2020, e20201576; DOI: https://doi.org/10.1542/peds.2020-1576

Age-dependent effects in the transmission and control of COVID-19 epidemics

Nicholas G. Davies, Petra Klepac, Yang Liu et al. Nature Medicine June 2020; DOI: https://doi.org/10.1038/s41591-020-0962-9

Background

The COVID-19 pandemic, which started in late 2019, has significantly affected most countries in the world. As a response many preventive measures have beeen implemented by National Health Departments. Preventive measures directed at children early in the pandemic included school and playground closures; however, the pediatric population has been less affected during this pandemic reflected by lower rates of infection and less severe disease (5-8% of cases). Understanding the role of age in transmission of SARS-CoV-2 is critical for determining which public health interventions will be most effective at controlling community transmission. These 2 recent articles describe the in vivo dynamics of infection transmission among families and a theoretical mathematical model of transmission and the impact on disease spreading.

Methods and results

The Swiss paper identified all patients under 16 years old with a diagnosis of SARS-CoV-2 infection by nasopharyngeal swab PCR during a one-month period at the peak of the pandemic. Parents and all household contacts were then identified. Authors reported 40 COVID positive children among a total of 4310 patients tested (0.9%) and 111 household members; parental interviews occurred at a median of 18 days following diagnosis. In the majority of cases (79%), an adult household member had suspected or confirmed COVID-19 before the study child; a child was the first to develop symptoms in only 8% of households.

In the 2nd paper the authors used a complex, age-structured, mathematical, dynamic model to evaluate the susceptibility, transmission and impact of interventions aiming to reduce transmission. They estimated, based on actual clinical data, that susceptibility in children under 20 years old is half that of adults and that clinical manifestations occur in approximately 21% in children between 10 and 19 years of age and increases to 69% when the infection affects elderly over 70 years. Then they made the assumption that children tend to make more social contacts (for example in school) than adults and, therefore, they should actually transmit more the virus than the adults. To determine the impact of school closure they compared projections for a city with high proportion of elderly individuals (Milano, Italy, median age 43 years), one with moderately aged population (Birmingham, UK; median age 30 years) and a city in a low income country with a high proportion of young individuals (Bulawayo, Zimbabwe; median age 15 years). From their mathematical models, authors found that school closure did not modify transmission rate and disease burden in any of the three cities under evaluation, and rates were similar compared to prior to school closure, indicating that children are less involved in disease transmission.

Comment

Both papers, even though with completely different strategies (one clinical-epidemiologic and one theoretical mathematic), come to the same conclusion: children are not major spreaders of SARS-CoV-2.

As was shown Davies et al, in countries with relatively younger median age the expected per capita incidence of clinical cases should be lower compared to countries with older median age population. There is also the assumption that subclinical cases are less infectious compared to visible symptomatic disease and this knowledge would be important for decision making.

At the beginning of the pandemic, school closures comprised one of the main public health interventions as children were considered important contributors to infection transmission based on influenza transmission dynamics. During the following months with increased understanding of COVID-19, even though discussion still continues and there are divergent opinions, it is more evident that children are less likely the major drivers of the epidemic. With the aim of decreasing transmission rates and public health burden, interventions should be designed to impart the most effective and impactful outcome; however, preventative strategies to minimize possible transmission by subclinical or asymptomatic cases should still be integral components of school re-opening plans based on growing evidence regarding how children are impacted by COVID-19.