Long-lasting symptoms from COVID-19 are rare in children, study finds

Children who develop symptoms of the novel coronavirus (COVID-19) typically get better after six days, and the number who experience symptoms beyond four weeks is low, according to a new study published in the journal The Lancet Child & Adolescent Health.

In the new study, the researchers used data collected through the ZOE COVID Study smartphone app, which includes data from more than 250,000 children in the United Kingdom ages 5 to 17 years old. Symptoms were reported through the app by their parents or guardians, rather than assessed directly in children, and the team did not collect data regarding school attendance.

The researchers focused on reports collected between September 1, 2020 and February 22, 2021. Some 1,734 children developed symptoms of COVID-19 and received a positive PCR test result close to the onset of symptoms, with their symptoms reported regularly until they were healthy again. This meant the researchers could accurately attribute these children’s symptoms to COVID-19 and could assess illness duration robustly.

Overall, the children were sick for an average of six days and experienced an average of three symptoms in the first week of illness, confirming that COVID-19 tends to manifest as a mild illness in children and that they usually recover quickly.

Most children recovered within four weeks, with a minority, 4.4 percent, experiencing symptoms after a. Typically, they had only two symptoms remaining after four weeks. The commonest symptom experienced by children with long illness duration was fatigue, the researchers said. Additionally, 84 percent of children were reported with fatigue at some point in their illness, and this was the most persistent symptom.

Headache and loss of sense of smell were also common, with each symptom experienced by 77.9 percent of children at some stage over the course of their illness. However, headache was more common early in illness whilst loss of sense of smell tended to occur later and to persist longer.

Of the 1,379 children who developed symptoms at least two months before the end of the study period, fewer than 2 percent experienced symptoms for longer than eight weeks.

Older children were typically ill for longer than primary school aged children, with an average illness duration of seven days in children ages 12 to 17 years old versus five days in children ages 5 to 11 years old. Older children were also more likely to have symptoms after four weeks than younger children, 5.1 percent of children ages 12 to 17 years versus 3.1 percent ages 5 to 11 years old, but there was no difference in the numbers of children who still had symptoms after eight weeks.

Importantly, the researchers also assessed the children who tested negative for COVID-19 who may have had other childhood illnesses, such as colds and flu. To do this, they randomly selected a group of age-matched and gender-matched children with symptoms reported through the app who were tested at the same time as the positive children.

Children with COVID-19 were ill for longer compared to children with other illnesses who tested negative for COVID-19, an average of six days’ illness with COVID-19 versus three days with other illnesses and were more likely to be ill for more than four weeks, 4.4 percent with COVID-19 versus 0.9 percent for children with other illnesses. However, at four weeks, the small number of children with other illnesses tended to have more symptoms than those who were ill with COVID-19, with an average five symptoms in COVID-negative group versus two symptoms in COVID-positive group.

The authors noted some limitations to their findings. They could not cross-check the symptoms reported by parents and guardians with health records, noting that most children were managed in the community, and there may be inconsistencies in the way people interpret symptoms on behalf of their children. Crucially, only children who had an adult who was participating in the COVID Symptom Study were able to participate, which may bias participation towards certain demographic groups.

The researchers also said that their findings on the number of children experiencing prolonged symptoms are lower than the most recent figures from the U.K. Government’s Office of National Statistics (ONS). They say this discrepancy may arise because of differences in way the two studies define the end of COVID-19 illness. The current study also allowed for children to have relapsing and remitting symptoms, allowing for periods of a up to a week of being completely healthy. When the ONS used similar cut-offs, the differences between the figures reported here and the ONS data were quite similar. Additionally, ONS estimates are based on data collected monthly, which relies on individuals remembering details of when symptoms were experienced, whereas the COVID Symptom Study collects data in real time.

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