Children have a similar prevalence of COVID-19 antibodies to adults, but more than 99% have mild symptoms

09 June 2020

A study made by SJD Barcelona Children's Hospital in more than 400 homes reveals that 17.5% of children who have had contact with a sick adult have become infected

The Kids Corona study at the SJD Barcelona Children’s Hospital has monitored 724 boys and girls who have lived at home with a coronavirus-positive parent
Approximately 17.5% of these children were infected with COVID-19, a figure similar to that of adults infected through household contact with an infected person, which is 18.9%
The Hospital will conduct a research project in summer camps to determine children’s capacity to transmit the virus

The Kids Corona platform, which the SJD Barcelona Children’s Hospital launched two months ago to study the incidence and impact of COVID-19 on children and pregnant women, has already obtained some initial results. Although these results are preliminary and will continue to be expanded upon over the coming months, in light of the current scientific and social interest in this matter, the Hospital has decided to make them known.

Over the last two months, researchers from the Kids Corona platform have studied 411 families, with a total of 724 children, in which at least one of the parents has had the disease. In addition, the cases of children being treated at the SJD Barcelona Children’s Hospital with a confirmed diagnosis of COVID-19 or symptoms compatible with this disease are being studied, as are pregnant women treated at SJD, Hospital Sant Pau and Hospital Clínic.

Preliminary results of the home transmissibility study

The Kids Corona platform research team has visited the homes of 411 families who have agreed to participate in this study in order to collect various samples: a serology (or immunity) test for all members of the family group, and a PCR test on the children in the household and on the parent with COVID-19 (the first parent to fall ill in the event that the disease has affected both parents).

The serology test has allowed researchers to discover that 17.5% of children living with a parent with COVID-19 have also contracted the virus. This percentage is very similar to that found in adults who have been in contact with an infected partner (18.9%). This leads the researchers to the conclusion that, when exposed to a source of infection, children are infected at the same rate as adults. But the disease is much milder in children than in adults, since over 99% of minors showed no symptoms, or if they did, they were insignificant.

In most cases, the family did not suspect that these children could have been infected as they had no symptoms or very mild ones, mainly fever, within the period of 7 days before to 14 days after the parent was diagnosed.

Moreover, with the PCR test, researchers have analysed whether the infected parents and children had the RNA of the virus in their nasopharynges and could theoretically transmit it to other people. The results of the analyses show that 33.8% of adults and 11.9% of children still had a viral load in the nasopharynx one month after the first case of coronavirus had occurred at home, although it was very low (with an estimated mean viral load of 2,500 copies/ml). There is currently no scientific consensus on the viral load needed to transmit the virus.

The study also seeks to identify any differential markers in children’s microbiota that can act as a shield against the virus. It also analyses the microbiota of children treated for COVID-19 to compare it with that of children treated for other respiratory infections. The results of this part are not yet available and will thus be released at a later date.

Fetalmaternal research studies

Researchers in this line — which is being conducted within the framework of BCNatal (Fetal Medicine Research Centre) in partnership with Hospital Clínic, and also includes cases from Hospital de Sant Pau — will analyse what factors determine the risk of COVID-19 in pregnant women and, if they are infected, whether they remain asymptomatic. Various factors are studied and data are provided to paediatricians so that they can monitor newborns.

To date, researchers have been able to analyse 874 pregnant women. A total of 14% of pregnant women have antibodies against coronavirus. Pregnant women infected in the first trimester (54 women) presented with milder symptoms, with 70% of women showing no symptoms, and 30% only mild symptoms. In infected pregnant women in the third trimester (71 women), however, there were fewer asymptomatic cases (52%), with 43.5% of women showing mild symptoms and 4.5% with pneumonia.

This is the first study of seroprevalence in pregnant women available on an international level. It greatly reduces the severity estimates made using published studies that point to increased severity of COVID-19 in pregnant women. When the study is completed, the impact on the pregnancy can be determined, as can whether the symptoms and risks of COVID-19 in pregnant women are the same or different in non-pregnant women.

Conclusions

The studies conducted to date by the Kids Corona platform have allowed researchers to conclude that:

Children are infected to the same extent as adults when they are in contact with a source of infection. The percentage of transmission of infection in children in the home environment is around 17%.
In children, the disease manifests mildly in more than 99% of cases.
COVID-19 affects 14% of pregnant women, the majority being asymptomatic or mildly symptomatic. The few pregnant women who present with more severe symptoms are those who have had the disease in the third trimester of pregnancy.

New studies to shed light on unanswered questions

The studies have not enabled offering a definitive answer on children’s capacity to transmit the virus. As a result, the Hospital plans to promote further research throughout this summer, to help clarify this issue with a view to returning to school this coming September. It will be a major unique project designed in collaboration with a group of Spanish and international experts, such as the BIOCOMSC of the Polytechnic University of Catalonia (UPC), ISGlobal or the Centre for Genomic Regulation, which will allow us to characterise results and better understand the epidemiology associated with COVID-19.

One of the studies, which will be conducted at summer camps in Catalonia, aims to determine whether children are transmitters of the disease in an environment very similar to schools. The research team of the Kids Corona platform will give children a weekly PCR. If a child tests positive in one of these tests, the team will apply the protocol defined by the Catalan Department of Labour, Social Affairs and Families and Health Department, and will exhaustively monitor all their direct contacts to determine if transmission has occurred.

In parallel, the Hospital will conduct other research work to detect newly diagnosed cases in primary care centres and other hospitals. These studies will be conducted in collaboration with the Catalan Health Department and will adhere to its line of action regarding COVID-19 and children.

Donations that have made the studies possible

All the studies promoted by the Kids Corona platform have been possible thanks to funding from civil society. Worthy of mention is a €500,000 donation from the Fundación Barça, based on a grant from the Stavros Niarchos Foundation, and which is part of the long-term alliance that these institutions started with the SJD Pediatric Cancer Center Barcelona project and which is once again underscored with the Kids Corona platform. Mention must also be made of the €200,000 donated by Banco de Santander.

The project has also received support from the Fundació Privada Nou Mil·lenni, Villa Reyes, Fundació Carmen i Maria José Godó and Immobiliaria Colonial, among other entities.

The BCNatal maternal-fetal research projects led by Dr. Gratacós also have the stable support of the Fundació "la Caixa".

Collaborating centres in the Kids Corona platform research projects

Partners

Hospital Clínic
Hospital de Sant Pau
BIOCOMSC de la UPC
ISGlobal
Centre for Genomic Regulation (CRG)
International University of Cataloni (UIC)
Fundación para el Fomento de la Investigación Sanitaria y Biomédica de la Comunidad Valenciana (FISABIO)

Alianzas en la investigación en pediatría