Covid-19 pandemic: What we know about Delta variant and children

Covid-19 cases among children are surging across the world amid Delta-fuelled outbreaks, spurring hospitalisations and raising concern about the risk of severe illness and persistent “long hauler” symptoms. It’s also prompted questions about the safety of schools.

How common is Covid in children?

In the US, as of September 16, more than 5.5 million children and adolescents had tested positive for the coronavirus since the start of the pandemic, according to the American Academy of Paediatrics. That represents 15.7 per cent of all cases, though individuals under 18 make up 22.2 per cent of the US population. However, after declining in early summer, paediatric cases have increased exponentially and comprise a higher share of the total — 25.7 per cent in the week ending September 16, or almost 226,000 cases. That surge, coinciding with increased circulation of the Delta variant, has translated into more Covid-related hospitalisations among children and adolescents, although serious cases remain proportionately rare.

Why are children being infected more?

Delta is at least twice as infectious as the original coronavirus strain that emerged in late 2019 and is causing more Covid-19 cases in susceptible individuals across all age groups. There’s no evidence that Delta is targeting children more than other age groups, but vaccination rates are higher in older people since adolescents generally got access to the shots much later. They still aren’t approved for children under 12. Vaccination of adults appears to prevent illness in children: Researchers at the CDC found emergency department visits and hospital admissions for children were higher in states with lower population vaccination coverage, and fewer in states with higher vaccination coverage.

How serious is a Delta infection for children?

Covid-19 remains a mild disease in the vast majority of children, and there’s no eviden­ce that Delta is changing that. Severe disease after any infection with SARS-CoV-2, the coronavirus that causes Covid, in children remains rare, and hospitalisation and death exceedingly rare. Often children are hospitalised for other reasons and coincidentally test positive for SARS-CoV-2. Some who have had Covid may later develop a rare but serious condition known as Multi­system Inflammatory Syndrome in Child­ren, though the cause is unknown.

Why are children less likely to get severely ill?

Children have a more robust innate immune response than older adults. That typically enables kids to successfully counter the infection before it’s had a chance to spread to the lungs to cause pneumonia and the inflammatory cascade that can be life-threatening in seniors. It’s also possible that the routine paediatric immunisations that younger children receive boost their innate immune response.

Are children more likely to transmit Delta?

The Delta variant is inherently more transmissible and, therefore, will be more contagious between children, between adults, and between adults and children and vice versa. Studies and modelling of transmission patterns indicate that younger children and adolescents play a lesser role in spreading SARS-CoV-2 at a population level, and that prioritising vaccination in older age groups yields more population-level protection against Covid.

Should children get vaccinated?

The case for immunising children is much less clear-cut than it is with adults, who are at greater risk of getting seriously ill. Vaccines have received emergency authorisation for use on children older than 12 in the US and elsewhere, while studies are underway to assess the safety and effectiveness of shots for those younger. Pfizer Inc and partner BioNTech SE said their vaccine was safe and produced strong antibody responses in children ages 5 to 11 in a large-scale trial. Some kids who have chronic medical conditions are at a higher risk of getting really sick from Covid, which is why some authorities have listed them as a priority group. Any recommendations will need to weigh the risk of harm from Covid against the risk of harm from the inoculation, as well as the broader benefits of vaccination, such as reducing transmission in the community and avoiding school closu­res. Researchers in Australia using modelling found herd immunity is unlikely unless children ages 5 to 15 are also vaccinated.

Can children get long Covid?

Yes, though it’s uncertain how frequently it occurs. An analysis and review of published studies by researchers in Switzerland and Australia found that long Covid might be less of a concern in children and adolescents than in adults, with symptoms typically persisting for less than 12 weeks. Still, the authors found that studies of the likelihood of persistent symptoms in children are limited and difficult to interpret. In some cases, children who had an infection weren’t compared with uninfected “controls” to identify whether chronic fatigue, anxiety and other ailments could be indirect consequences of the pandemic, such as lockdowns and school closures. In one large, self-selected, online study, only 13.5 per cent of eligible participants responded, leading to a potential response bias, for ex­ample, toward those experiencing lingering symptoms being more motivated to participate, resulting in an over-representation of symptom prevalence.