Health

Covid-19 has affected older people more severely than children, but scientists are increasingly concerned about long Covid in young people. By Manuela Callari.

Kids and long Covid

A man and child on Main Beach at the Gold Coast.
Credit: AAP / Jono Searle

Children have been largely spared the most severe symptoms of the Covid-19 infection, but as vaccines increasingly protect the adult population, the Delta variant is spreading quickly among young people.

Although acute infection in children still tends to be milder than in adults, countries such as Britain and the United States have seen a surge in children hospitalisations. In Australia, Covid-19 transmission among children has increased, too.

“There’s an increase in transmission across the whole population from children, to teenagers, young people and older people,” says Professor Robert Booy, a paediatrician and infectious diseases expert at The Children’s Hospital at Westmead and senior professorial fellow at the National Centre for Immunisation Research and Surveillance. “Delta goes for the fertile country; it goes for people who are not immune.”

In the past fortnight, children and teenagers have made up more than 30 per cent of all cases in New South Wales, with 953 infections among 10- to 19-year-olds from August 10-16.

Often the symptoms in children are very mild, but concerns are growing that, like adults, they are at risk of long Covid where they have problems that continue after recovery from the original infection. Some scientists have begun to worry that long Covid could potentially cause more harm to children than acute infection.

Research on the impact of Covid-19 on children is urgently needed, says Associate Professor Asha Bowen, a paediatrician at Perth Children’s Hospital and head of Skin Health at the Wesfarmers Centre of Vaccines and Infectious Diseases at the Telethon Kids Institute. Because only a few children have caught the infection and the illness is mild in most of them, the research effort has focused predominantly on adults, she says.

“We need to do more studies to understand how best to provide medical care for children, as well as to help families understand whether their children might have long Covid.”

This research is crucial to informing school reopening and vaccine rollout policies. In Australia, the Therapeutic Goods Administration has recently approved the Pfizer Covid-19 vaccine for children as young as 12 years old. Yet considering the sluggish vaccine rollout in our country, it might be a long time before children receive their shots.

In April, an Italian research group at the Gemelli University Hospital in Rome published a cross-sectional study that looked at 129 children aged six to 16 years who had been diagnosed with Covid-19 between March and November 2020. This study was the first attempt to quantify long Covid in children.

They found that more than one-third of the children had one or two symptoms four months after the acute infection. Another one-quarter of them had three or more symptoms.

Interestingly, even children who had experienced only mild acute infection, or were asymptomatic, reported long-lasting symptoms. The most common complaints were insomnia, fatigue, muscle pain and flu-like symptoms.

In a separate, larger study, published as a preprint in March, researchers surveyed the parents of children with persisting symptoms after Covid-19, predominantly in Britain and the US, between January 2020 and January 2021. They found similar results. Out of 510 children, 87 per cent experienced tiredness and weakness up to eight months after infection; 79 per cent had headaches; almost as many had abdominal pain. More than half had muscle and joint pain. Gastrointestinal symptoms and skin rashes were also common.

The study suggested that children with long Covid might manifest a number of neuropsychiatric conditions, such as difficulty concentrating, remembering and processing information and finding the right words when speaking.

More recent studies have been generally more positive. There are several reasons for this. The line between Covid-19 symptoms and pandemic symptoms is blurry, especially for children dislocated by home-learning and restrictions on their movement.

Another issue is that there isn’t an agreed definition of long Covid, so numbers might change depending on what symptoms are being looked at.

The largest study on long Covid in children so far, conducted in Britain, was published earlier this month in The Lancet. It found that lingering Covid-19 symptoms are rarer in school-age children than first thought.

Researchers at King’s College London looked at daily health reports logged by parents or carers on behalf of more than 250,000 children aged five to 17. The children had been hospitalised between March 2020 and February 2021 for various reasons, and nearly 7000 of them also tested positive for Covid-19.

The researchers found that fewer than one in 20 children with symptomatic Covid-19 acute infection experienced symptoms lasting longer than four weeks, and almost all children fully recovered within eight weeks.

“I think this data is reassuring to parents, teachers, and those children who are affected,” Professor Emma Duncan of King’s College London, one of the authors of the study, said at a press conference. “Our data says that although some children do have prolonged symptoms duration, most children will get better with time.”

According to data released by Britain’s Office for National Statistics in April, only 9.8 per cent of children aged two to 11 years old and 13 per cent aged 12 to 16 reported at least one symptom five weeks after contracting Covid-19.

These numbers are in accord with the most recent study from Australia, which followed 171 children from households who attended Melbourne’s Royal Children’s Hospital during Victoria’s second wave last winter. Most children in this study had a mild infection or were asymptomatic, and only a handful was briefly admitted to the hospital for observation or rehydration.

“Only a very small proportion [8 per cent] had persistent symptoms beyond a few weeks, and all of them had resolved by three months,” says Dr Shidan Tosif, a paediatrician at The Royal Children’s Hospital and one of the authors of the study. “Our research suggests that [long Covid] is a very rare outcome in children.”

Tosif says most studies on long Covid in children, including the one he conducted, have several limitations, which might explain the vast discrepancy between results. He says there is an urgent need to conduct larger studies that include a control group and harmonise the definition of long Covid.

It is also crucial to discriminate between the direct and indirect impact of Covid-19 on children, he said – lockdowns, restricted education and fewer social interactions can have long-lasting effects on children’s physical health, separate from the impact of the actual infection. “The indirect impact [of the pandemic] on mental wellbeing, which is really profound, can cause some of those symptoms even if you don’t have Covid.”

This double impact of the pandemic in children was observed in a German study published as a preprint in The Lancet last May. Researchers took blood samples and surveyed more than 1500 secondary-school children in Dresden from May 2020 to April 2021, to track rates of infection and symptoms of long Covid. Nearly 200 of them had antibodies indicating previous Covid-19 infection.

Surprisingly, the researchers reported no difference in rates of long Covid symptoms in the two groups. According to the authors, the result suggests long Covid in children might be less common than previously thought and emphasises the impact of pandemic-associated symptoms regarding the wellbeing and mental health of young adolescents.

Tosif says understanding what element of the immune system protects children from severe acute infection can give us clues on whether they are also protected from long Covid.

At The Royal Children’s Hospital in Melbourne, Tosif and his team are running a long study on children who have tested positive for Covid-19 and their families to understand how children’s immune response differs from adults.

In the meantime, encouraging news comes from the July report on long Covid from Britain’s Office for National Statistics, which says the two doses of the Covid-19 vaccine reduce by half the odds of experiencing long-lasting symptoms after post-vaccination infection in all age groups.

“In the future, children will probably need to be vaccinated,” Tosif says. “But right now, the best thing to do is for eligible adults to get vaccinated. That is the best way to prevent this infection from being transmitted generally and therefore in children.”

This article was first published in the print edition of The Saturday Paper on Aug 21, 2021 as "Kids and long Covid".

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Manuela Callari is a freelance science writer.