Vaccination against SARS-CoV-2, the virus that causes Covid-19, provides moderate protection against long Covid, which can cause long-term serious acute illness, in children and adolescents, according to a study.
Vaccination also has a stronger effect in adolescents, who have a higher risk of developing long Covid than young children, said researchers from 17 health systems in the US, in work led by investigators at the Children’s Hospital of Philadelphia (CHOP) in Pennsylvania, US.
While overall severity of Covid has been lower in children than adults, the burden of long Covid has been difficult to accurately describe since the symptoms can vary widely and the exact ways the virus causes them are unknown. Some symptoms include brain fog, dyspnoea, gastrointestinal dysfunction, generalised pain and fatigue, while others are more acute, like inflammatory reaction or heart problems.
“To date, no studies have assessed clinical data for large, diverse groups of children to address this important question,” said lead author Hanieh Razzaghi, from CHOP.“Using clinical data from across health care networks allowed us to have a large enough sample of patients to identify rare effects of the virus and its impact on children,” Razzaghi added. The findings were published in the journal Pediatrics.
Data from 17 health systems were used to assess vaccine effectiveness against long Covid in two groups of patients between 5 and 11 years old and 12 and 17 years old, respectively, as well as the time period in which patients were impacted. The vaccination rate was 56 per cent in the cohort of 1,037,936 children.
The incidence of probable long Covid was 4.5 per cent among patients with Covid, though only 0.7 per cent of patients were clinically diagnosed with long Covid. The study estimated effectiveness of the vaccine within 12 months of administration as 35.4 per cent against probable long Covid and 41.7 per cent against diagnosed long Covid.
The estimate was higher in adolescents compared with younger children (50.3 per cent vs. 23.8 per cent), and higher at six months (61.4 per cent) but decreased to 10.6 per cent at 18 months. Children who were vaccinated after recovering from Covid also appeared to benefit, with vaccine effectiveness of 46 per cent against probable long Covid after a subsequent episode of Covid.
“This study provides us with important data showing the protective effects of the vaccine against long-haul Covid and suggests that this protection is mostly from preventing visible infections. We hope this means that as vaccines are improved to be more effective against current strains of SARS-CoV-2, their protection against long Covid will get better, too,” said Charles Bailey, Associate Professor of Pediatrics at CHOP.
“These retrospective data provide guidance for additional research into the ways long Covid develops, and how we can better protect children and adolescents,” Bailey added.