COVID-19 days fewer in children; experts explain why

Most symptomatic children who tested positive for SARS-CoV-2 recovered within a week, and only a small subset of children experienced lingering symptoms in the COVID Symptom Study, one of the largest UK citizen participatory epidemiological studies thus far.

“We’ve confirmed that COVID-19 in children is usually mild and of short duration, with low symptom burden. Though some children experienced prolonged illness duration, they recovered with time,” said researchers from the UK. “Symptom burden did not increase with time, and most children recovered by day 56.” [Lancet Child Adolesc Health 2021;doi.10.1016/S2352-4642(21)00198-X]

“It is reassuring that the number of children experiencing long-lasting symptoms of COVID-19 is low,” said lead author Dr Emma Duncan from the King’s College London in London, UK. “Still, there’s a small number of children who experience long illness with COVID, and our study validates these experiences.”

Duncan and her team analysed illness duration and symptom burden in symptomatic school-aged children – 588 were aged 5-11 and 1,146 were aged 12-17— who had SARS-CoV-2. Data for children negative for SARS-CoV-2 were also analysed.

The most common symptoms reported in those with COVID-19 were headache (62 percent) and fatigue (55 percent), with a median illness duration of 6 days. A total of 77 children (4.4 percent) experienced symptoms for at least 28 days, which was more common in older children (5.1 percent vs 3.1 percent in younger children). Only 25 children had symptoms for at least 56 days.

In children who had symptoms for longer, the symptom burden was low after day 28 (median 2 symptoms) compared with the first week of illness (median 6 symptoms).

Children with non-COVID illnesses recover quickly

As for children who tested negative for COVID-19 and may have had other illnesses (eg, colds or flu), they recovered more quickly and were less likely to have lingering symptoms vs those with COVID-19. They were ill for 3 days on average and only 0.9 percent of the children had symptoms that lasted at least 4 weeks.

Overall, only 46.4 percent (805) of children who tested negative for COVID-19 had fever, cough, anosmia, or a combination of these symptoms. Few children who tested negative had an illness duration of 28 days or longer (0.9 percent), but they had a greater symptom burden than those who tested positive and whose illness lasted 28 days or longer.

“Our data emphasize that other childhood illnesses might have also protracted burdensome courses, requiring consideration in post-pandemic service planning,” the researchers said. “This also calls for a holistic approach in managing these children.”

Why children fare better than adults

Paediatric experts have a better explanation as to why “long COVID” may be less common in children than adults.

Dr Kevan Herold, professor of immunology and internal medicine at Yale University, said children have a very robust, innate immune response. “Our belief is that it seems to be protective and stops the virus at first encounter.”

“The children’s immune system mounts this really quick and effective immune response that shuts the virus down before it has a chance to replicate,” added Melanie Neeland, an immunologist at the Murdoch Children’s Research Institute in Melbourne, Australia.

Nevertheless, it is still important for children to get vaccinated, said Dr Betsy Herold, paediatric infectious disease specialist at Montefiore Medical Center in the Bronx, New York City, US. “Although they are less likely to develop severe disease, they can still transmit the virus to more vulnerable adults.”