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Freelance health journalist and former neuroscientist interested in a wide variety of life science topics. David also writes for The Guardian, BBC, National Geographic, NBC News, Wired, TIME and others.
Over the past month, the rise of Omicron and its associated subvariant BA.2 has once again thrown the spotlight on Long Covid, and in particular, its prevalence in children.
Previously, children were thought to be at far less risk of developing longer term sequelae from Covid-19 because its prevalence and severity is lower in teenagers and younger children, partly because they have fewer ACE2 receptors – the keyhole that the virus uses to access our cells.
However with the rise of ever more contagious variants – some data suggests that BA.2 is 33% more infectious than Omicron – more children are being affected. For example, around 80 children under 5 in the UK are being hospitalised with Covid-19 each day, a rate which is three times higher than last summer.
There are already indications that this is leading to greater rates of Long Covid, the now ubiquitous term for a whole range of symptoms which can include fatigue, insomnia, joint pain, respiratory issues, skin rashes and heart palpitations, lasting many weeks or months following Covid-19 infection.
According to Carlos Oliveira, a pediatric infectious diseases doctor at Yale Medicine, the Yale New Haven children’s post-Covid care program received three times as many referrals in January 2022 compared to August-November 2021.
“Long Covid is a problem in children because in some ways, they’re the most vulnerable population,” says Daniel Munblit, professor of paediatrics and infectious diseases at Sechenov University, who ranks no.2 on Insciter.com for topic citations on Long Covid in children.
“They may have to live with this condition for a very long period of time because they’re young and they have years and decades ahead of them. We don’t know how long some of these consequences will last.”
The biggest question surrounding Long Covid in children is figuring out exactly how prevalent it is, with estimates varying widely. One study last April of 129 children who had tested positive for Covid-19, found that 43% were still experiencing at least one symptom, more than 60 days after their initial infection.
In one of the biggest studies to date, scientists at University College London and Public Health England surveyed 3,065 teenagers who had tested positive for Covid-19 between January and March 2021. They found that somewhere between 2% and 14% were experiencing fatigue, shortness of breath and persistent headache, 15 weeks later.
“I think this variability in prevalence is due to a number of reasons,” says Danilo Buonsenso, a paediatrician at the Gemelli University Hospital in Rome, who ranks no.2 on Insciter.com for topic citations on Long Covid in children. “The definition of Long Covid is an issue, and it also depends a lot on the setting. I am one of the doctors looking into Long Covid and so more patients come to my attention. And this can be an explanation of why I report a higher number of cases.”
Buonsenso believes that there are at least 10% of children who test positive for Covid-19, and still report symptoms 12 weeks later. Some doctors suspect that this may be rising closer to 20% in the wake of Omicron and BA.2.
Given the sheer numbers of young children and teenagers who are now being infected, accurate surveys of Long Covid in this population are becoming ever more vital. “Even if the prevalence of Long Covid in children is 2%, given the thousands and thousands of children who will get Covid-19, that is a very massive number, which will really put a huge stress on our health systems,” says Buonsenso.
There are a whole range of theories for why children are developing long term symptoms as a result of Covid-19.
One hypothesis is that remnants of the SARS-CoV-2 virus linger in various pockets or reservoirs in the body, and continue to seep into the bloodstream continuously, triggering a reaction from the immune system. Another idea is that Long Covid is an autoimmune disease in which the presence of the virus triggers the patient’s own antibodies to attack their own tissue, causing damage long after it has left the body.
Munblit is particularly interested in a potential connection between susceptibility to allergies and Long Covid in children, although he admits that the evidence for this is still limited. One of the main theories for allergic reactions is an imbalance in the body’s Th1 and Th2 white blood cells, and Munblit thinks this could feasibly be a contributory factor to Long Covid symptoms.
“I’m more into thinking that Long Covid may be a result of Th1/Th2 imbalance, both in adults and children,” he says. “There may be some changes to the Th1/Th2 balance which leads to these consequences.”
Others have suggested that an unbalanced gut microbiome could make certain children more vulnerable to developing Long Covid, with viral particles residing in the gut and then getting absorbed back into the bloodstream.
Many major healthcare institutions such as the US National Institutes of Health, have begun to dedicate millions of dollars of funding towards projects studying Long Covid, which may soon yield some more concrete answers.
However Buonsenso says that research is still hindered by a persisting belief among some researchers that Long Covid is psychological. “Many researchers are still thinking that this is a psychological problem and until we all recognise that this is a medical problem, it will be very difficult to have ethics committees that approve clinical trials to understand the mechanistic causes and treatments that will benefit these children,” he says.
One of the main reasons why Long Covid is becoming a growing problem in children is because there is a far greater proportion of adolescents and younger children who remain unvaccinated. Vaccine availability and uptake for children around the world has consistently lagged behind adults.
In the US for example, the Centers for Disease Control and Prevention did not recommend the Pfizer-BioNTech vaccine for 5-11 year olds until November 2021, and under 5s are still not eligible. Current statistics show that only 20% of 5-11 year olds in the US are fully vaccinated, and just 55% of 12-17 year olds.
Oliveira is particularly interested in some studies which have suggested that administering Covid-19 vaccines to children suffering from Long Covid, who have yet to receive a jab, can help alleviate symptoms.
“The idea is that if there are remaining antigens or parts of the virus that are there, increasing the vaccine antibody may lead to clearing of those antigens,” he says.
Just as in adults, studies are ongoing to see whether antiviral medication or anti-inflammatories can yield benefits, but Buonsenso is keen to reassure concerned parents that in the majority of cases, the symptoms resolve relatively quickly.
“The good thing is that most children with Long Covid recover after three months,” he says. “So far, I’d say between two thirds and three quarters recover. But there are a subset of children in my cohort, that still six months afterwards, complain of persisting symptoms. Fatigue is the main problem, some of them have chest pain. In one child, we found chronic pericarditis which was not present before he developed Covid-19. These are the children for which we are proposing more investigations.”
This work on Long Covid could also help scientists understand more about why some children develop long-term symptoms from other viral infections, such as Epstein-Barr and Respiratory syncytial virus.
“In the past we have experienced a massive long term problem with Epstein-Barr virus infections, and other viruses, such as enteroviruses,” says Buonsenso. “Now, the main difference is that it’s happening all at once. Now we have thousands of patients fighting for their condition to be understood. This is an opportunity to understand the post-viral world, which so far has been really neglected.”
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