Are children infectious? New data and need for further investigation
To date, it seems clear that children have milder symptoms of COVID-19 and that a significant proportion of child sufferers are asymptomatic. However, it is still unclear whether and to what extent they can nevertheless transmit the disease. While schools have been closed in most countries as part of the strategy to contain the COVID-19 pandemic, in Sweden day care centers and schools for children up to 15 years of age remained open. A recent study of all pediatric hospital admissions in the Stockholm region, where all children were tested for COVID-19 regardless of why they were hospitalized, shows that the percentage of adolescents with COVID-19 aged 16-18 (16%), for whom education was taking place by distance learning only, was similar to the percentage of children aged 1-5 years (17%). In addition, the observed incidence of severe illness among Swedish children was low. These results, compared with those from other countries that implemented country-wide school closures, suggest that keeping schools open did not worsen the spread of the pandemic for children in Sweden, although further studies would be needed to elucidate the impact of opening schools on the overall transmission of COVID-19, not only among children but also from children to adults and the potential impact on their hospitalizations.
Another study from China has estimated the risk of infection for household versus non-household transmissions by age group. By creating and analyzing a database with detailed information for over a thousand transmission pairs reconstructed from more than nine thousand confirmed cases of COVID-19, the study estimates that the risk of being infected outside households is higher for people aged between 18 and 64 years, whereas children and adolescents (<18), as well as older people (>65), have a higher risk of being infected within their homes. Although in this study, there were no recorded instances of children younger than 18 years acquiring COVID-19 from other children in the home, this may be related to the usual household composition in Chinese cities, where families of three with an only child are common. Along this line, a recent report based on data from 81 countries underlines the already stated importance of considering the population's age structure and coresidency patterns, defined as how big households are and how old their members are, in order to determine the vulnerability of each country to outbreaks of COVID-19. This in turn would define how effective general and age-specific household confinement policies can be in reducing mortality during and after an outbreak.
Future studies on summer camps and schools will be key to finally elucidating whether children are infectious and, if so, to what extent. Nonetheless, in many countries school closure was the first measure taken to reduce the spread of the pandemic and has been or will be one of the last to be kept in place. Importantly, the potential negative consequences of school closure on children beyond the COVID-19 infection have been and continue to be widely commented by the research community and will also need to be considered by governments around the world.
First results from the study of seroprevalence in pregnant women within the Kids Corona project
A multicenter study, included in the Kids Corona project, from three hospitals in Barcelona has evaluated the seroprevalence and clinical presentation of COVID-19 in 874 cases of pregnant women in the first and third trimester. The results, so far available as a preprint, show that 14% of pregnant women have antibodies against SARS-CoV-2, a substantially larger proportion than the present rates of PCR positive cases reported for women aged between 20 and 40 years in Barcelona (0.78%), and most have developed the infection asymptomatically or with mild symptoms. Although the susceptibility to infection seemed to be the same in the first or third trimesters of gestation, the few pregnant women with more severe symptoms were those who contracted the infection during the third trimester, which is in line with earlier reports. These data show a reduced number of cases requiring critical care than those previously found by PCR testing (9%) and highlight the value of seroprevalence studies to capture the high proportion of asymptomatic or mild infections.
Demographic and socioeconomic data associated with COVID-19 infection among pregnant women
Pregnant women with COVID-19 appear to generally experience a mild clinical course and have similar risks of developing a severe case of the illness to the non-pregnant population. However, they are nevertheless considered a vulnerable group within the COVID-19 pandemic. A recent investigation in universally tested pregnant women from New York City has aimed to study potential associations between the infection in pregnant women and their demographic characteristics and socioeconomic status. The study finds that COVID-19 transmission is associated with large household membership, household crowding, and low socioeconomic status. These data may aid the identification of population subsets at higher risk of infection within an already vulnerable group.
A study made by SJD Barcelona Children's Hospital · Instritut de Recerca Sant Joan de Déu reveals that 17% of children who have had contact with a sick person have become infected. Children have a similar prevalence of COVID-19 antibodies to adults, but more than 99% have mild symptoms.