Children and COVID-19: The Evidence

As schools make decisions about re-opening, and parents make decisions about their children, they need answers to questions like these: Are there cases of COVID-19 occurring in schools, and if so, how many?

The Washington Post has linked to a Google spreadsheet built by a teacher in Olathe, Kansas, Alisha Morris.  There are over 700 entries so far, with annotations to report details about each one. 

Right away, the notes in this dataset bring up an important point. While the discussion about schools revolves to a considerable extent about the disease's prevalence and effects in children, schools are in fact occupied by children, teachers, administrators, and other staff: lunchroom, custodial, bus drivers. There are four transmission channels of COVID-19 to consider: 

1) child to child 2) child to adult

3) adult to child

4) adult to adult

In addition, for both children and adults, transmission can occur when COVID-19 is contracted outside of the school (primarily from home), and brought to school, or when COVID-19 is contracted in school and taken to contexts outside of school). 

For decision-makers, the takeaway is that understanding what will happen as schools re-open cannot be based only on the observed characteristics of COVID-19 in children. 

Can children spread COVID-19? 

While it is known that more cases of COVID-19 have been recorded among adults, especially older adults, that does not mean that there is necessarily some inherent interaction between the coronavirus and children's immune systems which protect them. The observed numbers have been collected while schools are closed. In order to draw reliable conclusions about the infectiousness of COVID-19 in children, researchers would have to have known populations (infected vs non-infected) in controlled conditions. Those conditions would have to include knowing exactly whom children come into contact with both inside and outside school, and exactly how they behave when in the presence of others (masks, social distancing).

Percentages of children infected could be an artifact of how tests are made available, particularly in communities with shortages. If it is true that children overall tend to have milder forms of the disease, then untested children will not appear in the data, giving the illusion that children mostly do not contract the disease. 

A study from Europe which reviewed available reports from a variety of national school contexts supports the hope that when children do contract COVID-19, they tend to suffer milder cases, as long as they do not suffer from pre-existing risk factors such as childhood obesity or diabetes. However, this study also reports research indicating that the viral load of children when infected is the same as that of adults, and that this viral load is highest in the first week of infection. Since the first week of infection often includes the period of mild or no symptoms, the danger of spread through unidentified cases remains. 

On the question of whether outbreaks can occur through children at all, the available evidence supports the idea that it can. A study of an outbreak in Israel records a significant outbreak affecting children from 7th through 12th grade, and adult staff. It is useful to see here that different age cohorts experienced different levels of infection.

Secondary spread was confirmed by tracing: "By mid-June 2020, 87 additional confirmed COVID-19 cases had occurred among close contacts of the first school’s cases. These included siblings attending other schools, friends and participants in sports and dancing afternoon classes, students’ parents and family members of school staff." In this outbreak, crowded classrooms made proper social distancing impossible, and seasonal heat kept classes mostly in closed classrooms with air conditioning.  Across the board, researchers conclude that school environments can entail significant risk. They especially urge that known measures of controlling spread - masks, cleaning, social distancing, limiting between-group contacts - be rigorously applied wherever school attendance is considered.

All opinions expressed in this blog are solely those of the authors, and do not reflect those of University of Texas Rio Grande Valley, or any organizations of which either is a member.