In a group of nonhospitalized children 0 to 16 years old, SARS-CoV-2 neutralizing antibody levels peaked at about 84% 1 to 3 months after they tested positive for COVID-19 but remain high for more than a year, finds a single-center study published yesterday in JAMA Pediatrics.

The study involved pre-Omicron strains and also found that antibody response in the first month after infection was most durable in participants younger than 5 years.

From Feb 1, 2020, to Sep 30, 2021, researchers in Singapore analyzed SARS-CoV-2 neutralizing antibody responses in 126 children aged 0 to 16 years for up to 16 months after COVID-19 diagnosis. Average participant age was 7.4 years, 58.7% were boys, and 30% completed two to four visits for blood sampling.

Antibodies still 70% at 9 to 13 months

All patients with COVID-19 symptoms (72%) had a mild illness. The most common symptoms were fever, cough, and a runny nose. No patients developed multisystem inflammatory syndrome in children (MIS-C).

SARS-CoV-2 neutralizing antibody levels peaked at a median of 84% roughly 1 to 3 months after infection and remained at roughly 69.8% after 9 to 13 months. An adjusted analysis showed no association between neutralizing antibody levels by time since infection and patient characteristics such as sex and symptom status.

In the first month after infection, children younger than 5 years had the highest antibody levels (71.6%; 95% confidence interval [CI], 58.5% to 84.6%), while those aged 12 to 16 had the lowest (49.9%; 95% CI, 41.3% to 58.6%). Neutralizing antibody levels remained stable in the younger group at all time points for up to 16 months.

"The findings suggest that risk of SARS-CoV-2 reinfection in younger children is lower than in adults, which has important implications for scheduling COVID-19 vaccination after infection," the study authors wrote. "The findings also broaden the understanding about less severe clinical disease in younger children."

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