Children are a low-risk group for coronavirus disease 2019 (COVID-19) following infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), with less than 2% of European hospitalizations with the disease being in children below the age of 19 years, and less than 5% in the USA, Spain, and China in 2020.
A current medRxiv* preprint discusses the current epidemiologic profile of this age group, following the massive rollout of vaccines and the emergence of different variants of the virus.
Study: Risk of SARS-CoV-2 testing, PCR-confirmed infections and COVID-19–related hospital admissions in children and young people: birth cohort study. Image Credit: Dragana Gordic/Shutterstock.com
Children with severe COVID-19 often present with fever, nausea or vomiting, and respiratory symptoms. Some weeks after the infection, a few children develop an acute inflammatory syndrome, pediatric inflammatory syndrome temporally associated with SARS-CoV-2 (PIMS-TS), or multisystem inflammatory syndrome related to COVID – MIS-C.
While those below 2 years have the highest risk of acute symptoms, children above 10 account for most PIMS-TS.
Earlier studies show that children with certain symptoms relating to the lungs, throat, brain, or heart, and especially if they have underlying illnesses, are at greater risk for severe COVID-19 and admission to the Pediatric Intensive Care Unit (PICU) admission or death. The highest risk is among infants and older children, the least being in children aged 0-4 years.
This data is important in determining the risk-benefit ratio of vaccinations in children. The current study, on the medRxiv preprint server, aims at helping make this decision clearer, by providing data on population-level risks of COVID-19 testing, confirmation of infection by polymerase chain reaction (PCR) testing, and admissions in children and young people (CYP) for this condition. The scientists attempted to compensate for age, other illnesses, and socioeconomic factors to derive a generalizable conclusion.
What Did the Study Show?
The study used data from a national Scotland birth cohort covering the years from 1997 onward, including only those who remained in Scotland throughout. Public health surveillance data was used to provide SARS-CoV-2 test results.
Covering over 1.2 million CYP, of which about 5% had one or more chronic conditions, the study results showed that COVID-19 testing had been carried out in over a fifth of the cohort. Most had been tested once, but one in seven had been tested twice, and 6% more than twice. This comes to a testing rate of >770/1,000 CYP-years.
The testing rates were highest for children aged 1-4 years, and those aged 18-22 years, as well as those with more than one illness. Children born preterm were more likely to receive a test below the age of 5 years than those born at term. For infants with chronic conditions, testing was more common.
PCR tests were positive in 5% of cases, and excluding multiple positive tests in the same children, this comes to PCR-confirmed infections in 7% of CYP, with an overall rate of ~180/1,000 CYP-years. Again, the highest rates were in those aged 18-22 years and the lowest among those aged 1-4 years.
Except for infants, who tested positive more frequently than other children below 5, age-linked infection rates were observed. Among children above 12 years, PCR-confirmed infections were more likely in higher socioeconomic strata but were less common if previous health conditions were present. For younger children, the opposite was observed.
Having one older child in the family reduced the risk of PCR-confirmed infection in children 1-4 years old by 36%, while for infants the decrease was by 14%. At the age of 12-17 years, a high body mass index increased the risk of being PCR-positive very slightly.
Less than 1% of all admissions were related to COVID-19, with only 25 re-admissions, and a two-day median stay, for an overall rate of admission due to COVID-19 of 29/1,000 CYP-years. Again, infants were admitted at 120/1,000, much higher than any other age group, but the proportion of admissions was highest among CYP with other health conditions. Nonetheless, almost 90% of admissions were in CYP without prior health conditions.
There were <350 admissions related to COVID-19 altogether, and only 13 (intensive care unit) ICU admissions. Half the ICU admissions were in children with one or more chronic illnesses, with a median age of 14 years, and a median ICU stay of 6 days. Half were boys. Less than five were admitted for PIMS-TS, all being boys, with a median 10-day ICU stay.
What Are the Implications?
Relatively high testing rates were seen among the CYP in this study, increasing with age. Less than 2% had a PCR-confirmed infection, with the highest rates in those aged 18-22 years. Testing was more common in those with chronic infections.
PCR-confirmed infection was more common in under-fives and older children >12 years, from lower and higher socioeconomic groups, respectively. Lower socioeconomic status was linked to a higher risk of admission.
This could indicate that parents from lower socioeconomic backgrounds were more likely to be occupationally exposed to infection and to pass it on to preschool children at home. Conversely, older children from such backgrounds may be less likely to attend colleges or other educational centers and are thus shielded from the infection. Further studies are required to explore this risk.
Admissions related to COVID-19 were very uncommon, with the highest rates being in infants and those with more than one chronic condition. This is the case for other injuries and illnesses, thus does not reflect a unique risk for COVID-19 in CYP.
The population-based nature of the study enabled variations with age, socioeconomic status and chronic conditions to be examined for their relationship with testing, confirmed infections, and admissions for COVID-19. However, during the study period, only the wildtype and Alpha variants of the virus were circulating.
Vaccination recommendations for high-risk children aged 12 years or more with two doses of the Pfizer/BioNTech vaccine were first introduced, in July 2021, but changed to one dose for those aged 16-7 years for fear of myocarditis, and eventually to one dose for all children above 12 years. In the US, however, the vaccine is approved for use in children above 5 years.
Admission risks even in infants are low, despite their having the highest admission rate among all CYP. It is only half that of admission for influenza or respiratory syncytial virus infection (at 1/1,000, 2/1,000, and 22/1,000 CYP-years, respectively).
Further studies are urgently needed to examine whether maternal vaccine during pregnancy prevents COVID-19 admissions in infants. These data also provide baseline risks of infection and hospital admission for risk-benefit assessments of childhood vaccination, particularly for preschool children.”
Given the small admission risks reported here, it is to be seen whether the vaccination program will help to significantly improve these risks, though it may reduce school absences – itself a controversial assertion with the emergence of new immune-escape variants of the virus. More such studies must inform the recommendations for universal pediatric vaccination against this overwhelmingly minor infection where children are concerned.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.