August 20, 2020

expert reaction to study claiming children are silent spreaders of SARS-CoV-2

A study, published in the Journal of Pediatrics*, has claimed that children are silent spreaders of SARS-CoV-2.

Prof Russell Viner, President of the Royal College of Paediatrics and Child Health:

“This study adds a piece to the jigsaw of evidence built up on children, COVID-19 and transmission, yet it is essential to recognise the limitations of the data in this study. This is a small study of 49 COVID-19 positive patients  presenting to one hospital – the majority being teenagers  – and tells us about viral load in symptomatic children and not in the general population. I am concerned about the authors conclusions regarding viral load, as their Figure 2A suggests this is based upon limited data from children (<30 swabs) and compares children in the first week with adults beyond the first week of symptoms. Yet evidence suggests that viral load drops after the first week of illness, as their data appear to show in both children and adults. So this comparison is unhelpful and potentially misleading.

“Previous studies have shown us that children can and do have viral loads similar to adults.  Viral load tells us about the potential for transmission of the individual child, not the reality of transmission by children as a group. Real-world data tell us that children can transmit this virus but that as a group they play only a limited role in transmission of this pandemic. The overall jigsaw of evidence remains reassuring about transmission by children and young people.”

Prof Adilia Warris, Professor of Paediatric Infectious Diseases at the University of Exeter, said:

“The data presented here does not support the claim that children are silent spreaders of COVID-19.

“The authors do show that children who presented with respiratory symptoms during this pandemic, and who tested positive for SARS-CoV-2, displayed viral loads comparable to adult hospitalized patients, especially in the first two days of symptoms.  Interestingly, of the children presenting with symptoms, only around 28 per cent of children tested positive,  and of these, more than 60 per cent were over the age of 11, 26 per cent were obese (with less than 10 per cent in the non SARS-CoV-2 group), and exposure to the virus was by either mum or dad (77 per cent), supporting a larger role for adults in the transmission of this virus.

“The study was not designed to assess risk of transmission. Although a high viral load contributes to the level of contagiousness, it is not the only factor playing a role. The study was performed in children presenting and/or admitted to hospital, which we know is different from children presenting to community practices, and therefore the conclusions and translations the authors make with respect to schools is in my opinion too far-reaching, and is not supported by the data they present.”

Dr Simon Clarke, Associate Professor in Cellular Microbiology at the University of Reading, said:

“In my opinion the headline of the press release is very misleading, because the study does not actually demonstrate that children spread the virus.

“It is already fairly well documented that children do indeed contract the coronavirus causing Covid-19 and that they produce it in large quantities.  However it is less clear how much infection they cause in others or how their age may influence that.  This study only adds to our understanding of the extent of infection in children, but not the spread of Covid-19.  It does not demonstrate, in any way, that children actually spread of the virus to adults or other children.”

Dr Andrew Preston, Reader in Microbial Pathogenesis at the University of Bath, said:

“In my opinion many of the statements in this paper are largely unfounded.

“The authors conclude that children can carry high levels of virus in their airways, even though displaying mild symptoms. They argue that children present a risk of transmitting the infection to others, which would be of great concern when considering the re-opening of schools.

“However, that is very misleading because the study was limited to symptomatic children. It is recognised that symptomatic individuals likely pose a greater risk of transmission than asymptomatic individuals. The discussion appears to suggest children in general will be walking around with high viral loads, when in fact this study was limited to small numbers of children with symptoms. Those displaying symptoms would be isolating, not walking around in schools.

“It is recognised that there could be a period before symptoms develop when a child might be shedding virus, but the low numbers of children who display disease means this would be relatively rare. The study does not include any appraisal of the transmissibility of the virus in the children studied, which is a significant weakness.

“The measurement of viral load in the respiratory tract detected viral RNA, not viral particles, so it is not clear that the high levels detected would equate to high infectivity.

“The study is a valuable contribution to the study of COVID-19 in children, but the paper makes some bold claims regarding the role of children as silent spreaders of the COVID-19 virus. Without studies of transmission, and while focused only on symptomatic children who are a minority of the whole children cohort, these claims are largely unfounded.”

* ‘Pediatric SARS-CoV-2: Clinical Presentation, Infectivity, and Immune Responses’ by Lael M. Yonker et al. was published in the Journal of Pediatrics on Thursday 20 August 2020.

DOI: https://doi.org/10.1016/j.jpeds.2020.08.037

Declared interests

None received.