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COVID: How different variants affected Canadian children

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A new study of more than 1,400 Canadian children who contracted COVID-19 found that fever and cough were associated more heavily with Omicron and Delta variants, but that serious outcomes like hospitalization and being moved to the intensive care unit remained even across all variants.

The fact that rates of hospitalization and being moved to the intensive care unit remained stable even with later variants could be a sign that when it comes to children, the virus is not getting milder, researchers said.

“Unlike in adults, it does not appear that children are being less severely affected by emerging variants, and understanding the clinical presentation of COVID-19 in children is needed to design therapeutic trials on this population,” researchers wrote in the study.

The question of how severe different variants are, and how they present differently across populations, is the one that researchers have posed for the entire pandemic.

In this new study, published Thursday in the peer-reviewed journal JAMA Network Open, researchers wanted to investigate whether children experienced different symptoms depending on which variant of COVID-19 they had contracted.

They looked at 7,272 children who had presented to one of 14 pediatric emergency departments between August 2020 and February 2022 and were tested for COVID-19.

Around 1,440 tested positive for the virus. Slightly more than half — 55 per cent — were boys, and the median age was two years old.

It’s known that different variants tend to affect the body differently, with previous research noting that Omicron variants have a tendency to infect the upper airways more easily than other variants.

But not many studies have observed this impact on children.

Compared to the original strain of COVID-19, both Delta and Omicron came with a higher level of fever and cough, this study found.

In terms of which part of the body the symptoms seemed to affect the most, upper respiratory tract symptoms were associated with Delta infection, while lower respiratory tract symptoms were more common with Omicron infection.

Children infected with Omicron were also more likely to have more systemic symptoms apart from just respiratory symptoms. Children infected with the Alpha variant had the fewest number of individual COVID-19 symptoms.

Despite the differences in symptoms produced by individual variants, there was no clear difference in the proportion of children hospitalized or admitted to the intensive care unit.

However, children infected with Omicron were more likely to have additional emergency department visits compared to those infected with Delta.

Patients with Omicron were also more likely to have a chest radiography performed, to be put on an IV during their hospital stay and to receive corticosteroid treatment.

“While several reports described Omicron as being responsible for less severe disease than prior variants, particularly among adults, we found that children with Omicron infection received more interventions and were more likely to experience ED revisits,” researchers wrote. “Our findings are not unique, as they align with other pediatric studies that report higher pediatric hospitalization rates during the Omicron period.”

All of the 14 Canadian pediatric emergency departments that data was pulled from are part of the Pediatric Emergency Research Canada network.

All patients included in the study were then contacted by phone a median of two days after their emergency department visit to gather demographic, clinical or epidemiological data, as well as data on any comorbidities.

Researchers also performed a follow-up two weeks later for 1,224 participants to see how cases developed. A total of 998 participants provided data on whether the child in question was vaccinated or not, with just eight per cent of them having received at least one dose.

In terms of the most common individual symptoms, 75 per cent of the cohort experienced fever, 56 per cent had a cough, and 53 per cent had a runny nose.

Infection with the Alpha variant came with the fewest number of symptoms considered “core” COVID-19 symptoms — fever, cough and loss of taste/smell. Out of all participants, 89 per cent of children experienced at least one of these three symptoms, and they were the most common among those with Omicron.

The Alpha variant also came with the lowest percentage of patients with drowsiness, pink eye, oral changes, a runny nose or a sore throat as a symptom.

Delta infection came with the highest percentage of patients with pink eye and cough as symptoms, with 61 per cent of Delta patients experiencing a cough.

Researchers noted that the proportion of children experiencing severe disease was lower than has been measured in previous research, stating that this could be because some emergency department visits included in this study were for the purposes of obtaining a COVID-19 test, and were not spurred by serious illness.

The study is also limited by the fact that only one third of the cohort got variant testing to be sure of which variant patients had. All other variant designations were decided by which variant was dominant in that region at the time the patient contracted the virus, meaning there could be errors in the data. The majority of Alpha and Delta patients had their variants confirmed with testing.